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Purpose: The purse seine fishery for sardine is the most important fishery in Portugal. The aim of the present study is to assess the environmental impacts of sardine fished by the Portuguese fleet and to analyse a number of variables such as vessel size and time scale. An additional goal was to incorporate fishery-specific impact categories in the case study. Methods: Life Cycle Assessment methodology was applied, and data were collected from nine vessels, which represented around 10 % of the landings. Vessels were divided into two length categories, above and below 12 m, and data were obtained for the years 2005 to 2010. The study was limited to the fishing phase only. The standard impact categories included were energy use, global warming potential, eutrophication potential, acidification potential and ozone depletion potential. The fishery-specific impact categories were overfishing, overfishedness, lost potential yield, mean trophic level and the primary production required, and were quantified as much as possible. Results and discussion: The landings from the data set were constituted mainly by sardine (91 %), and the remainders were other small pelagic species (e.g. horse mackerel). The most important input was the fuel, and both vessel categories had the same fuel consumption per catch 0.11 l/kg. Average greenhouse gas emissions (carbon footprint) were 0.36 kg CO eq. per kilo sardine landed. The fuel use varied between years, and variability between months can be even higher. Fishing mortality has increased, and the spawning stock biomass has decreased resulting in consequential overfishing for 2010. A correlation between fuel use and stock biomass was not found, and the stock condition does not seem to directly influence the global warming potential in this fishery. Discards were primarily non-target small pelagic species, and there was also mortality of target species resulting from slipping. The seafloor impact was considered to be insignificant due to the fishing method. Conclusions: The assessment of the Portuguese purse seine fishery resulted in no difference regarding fuel use between large and small vessels, but differences were found between years. The stock has declined, and it has produced below maximum sustainable yield. By-catch and discard data were missing but may be substantial. Even being difficult to quantify, fishery impact categories complement the environmental results with biological information and precaution is need in relation to the stock management. The sardine carbon footprint from Portuguese purse seine was lower than that of other commercial species reported in. [ABSTRACT FROM AUTHOR]

The northeastern offshore population of the pantropical spotted dolphin ( Stenella attenuata) in the eastern tropical Pacific remains listed as depleted under the Marine Mammal Protection Act, and recent estimates of abundance show that recovery has been slow. One hypothesis for the slow recovery is that continued chase and encirclement by the tuna fishery negatively affects reproduction. Insufficient life-history sampling in this region over the last two decades makes traditional estimates of reproductive rates impossible. Here, we examine the current reproductive patterns of these dolphins by measuring blubber progesterone (BP) concentrations in biopsy samples to assess pregnancy state. BP was quantified in 212 biopsies from female offshore spotted dolphins sampled between 1998 and 2003 in the northeastern tropical Pacific, and we found that 11.5 % of the biopsied females (mature and immature) were pregnant. The relationship between pregnancy and fishery exposure was analyzed, and we found that pregnant females were exposed to significantly less fishery activity than non-pregnant ones ( p = 0.022), suggesting that the fishery may have an inhibitive effect on pregnancy. Spatial analysis indicated that pregnancy was more aggregated than random ( p < 0.05) at a scale up to 180-nmi, with the highest proportion pregnant in the mouth of the Gulf of California, an area with relatively low reported fishery activity. [ABSTRACT FROM AUTHOR]

South Africa's small pelagics fishery is currently the largest in volume and second largest in value in the southern Benguela. It exploits short-lived, small pelagic fishes such as anchovy (for reduction into fish meal and oil) and sardine (for reduction as well as human consumption through canned products), and to a lesser extent redeye round herring and mesopelagics, largely for reduction. We explore the recent history (1940s to present) of the social-ecological system around this fishery. The natural subsystem, at the scales of the ocean environment and the ecosystem, is characterized by high interannual and documented decadal-scale variability. We characterize the human social subsystem at the scales of the fishing industry, legislation, and west coast fishing towns, and demonstrate interdependencies between the natural and social subsystems by following system-scale changes. The pelagic fishing industry has evolved to deal with variability through consolidation, diversification, and range expansion. Legislation has increasingly looked for conservation of the resource while ensuring economic viability of the industry, and hence factory- and vessel-related jobs. Fishing communities under apartheid stayed largely dependent on company-generated infrastructure, combining seasonal employment in the fishing factories with inshore fishing, targeting rock lobster and line fish. While the pelagic industry persisted and communities survived, the resource base for both offshore and inshore fisheries gradually eroded. The advent of democracy in the mid-1990s brought allocation of long-term fishing rights to individuals or companies under conditions of depleted inshore resources aggravated by a shift in the distribution of pelagic fish away from the west coast towards the Cape south coast in the second half of the 1990s. The resultant loss of employment and fishing rights in the inshore has generated community coping strategies that include poaching and challenges to the current Marine Living Resources Act, while the industry continues to expand by range and species, possibly further eroding the resource base. We argue that the situation in the pelagic social-ecological system is indicative of further loss of resilience to change. Coping with future longterm, system-scale change will necessitate careful long-term scenario planning among the various interest groups involved, joint research being one way to overcome the communications breakdown and initiate the joint planning process. [ABSTRACT FROM AUTHOR]

Changes in hydroxyl lipids (L-OHs; a stress level indicator), body weight, triglycerides, fatty acids, and free amino acids (FAAs) were investigated inDecapterus maraudsicaught by purse seine from two different ocean regions near Japan to determine the effect of short-term holding without feeding on the reduction in oxidative stress. In experiment 1, the L-OHs in the dorsal muscle significantly decreased by 9 d, whereas those in the liver decreased significantly by the end of the 33-d holding period. The body weight, lipid content, and triglyceride composition did not change significantly for 9 d and then decreased significantly by 33 d. Fatty acid composition of the dorsal muscle and liver did not change significantly within the holding period. The FAA content in the dorsal muscle did not change until 9 d and then decreased by 33 d. In experiment 2, the L-OHs in the dorsal muscle had significantly increased at 33 d, whereas the levels in the liver of the fish after transport to port were twice as high as those in the fish that had just been caught, but then they decreased significantly by the end of the holding period. The change in body weight, lipid content, and triglyceride composition were the same as in experiment 1. The fatty acid compositions changed at 33 d, and the total FAA content did not change until 20 d and then decreased at 33 d. Both results suggest that to avoid stress and to obtain a higher quality fish product, fish captured by purse seine should be held without feeding for 8–9 d rather than immediately shipped after capture. The results of this study may be useful for improving the quality and commodity value of fish captured in commercial fisheries, such as by purse seine, and those held in aquaculture operations, such as in sea cages. Received March 12, 2013; accepted July 26, 2013 [ABSTRACT FROM PUBLISHER]

Seasonal variation in daily growth rates in the early and middle larval stages of round herring Etrumeus teres were largely determined by the sea temperatures experienced by hatch-date cohorts in the Pacific coastal waters off southern Japan. Round herring larvae were collected by purse seining in the coastal waters of central Tosa Bay. A total of 451 larvae were aged by reading daily rings in otoliths. Individuals within a range of 2-5 hatch dates were grouped as hatch-date cohorts. We selected 16 cohorts that hatched during September 2000 and March 2002 and calculated mean widths of otolith growth increments for each cohort during the first feeding stage ( W, increments 1-5) and the maximum increment width in the middle larval stage ( W). Seasonal variation in mean W and W among the 16 cohorts was largely (80-90 %) explained by the sea temperature in the bay. These results indicate that temperature was a predominant determinant of larval growth rates; other environmental factors, such as food availability, did not substantially affect growth rates of round herring larvae in coastal waters along the subtropical Kuroshio Current off southern Japan. [ABSTRACT FROM AUTHOR]

Abstract: We initiated the first cage culture of the Mediterranean horse mackerel (Trachurus mediterraneus) in the Black Sea. The wild fish was captured by purse seine and transferred into sea cages. Fish were fed by sea bass feed during grow out period, but fish mortalities were observed. However, the causes of mortalities were unknown. Therefore, cultured Mediterranean horse mackerel have been sampled monthly for two years to determine possible parasitic and bacterial agents. During the study, no parasite was found while several Gram negative bacterial species including Aeromonas hydrophila, Chryseobacterium indologenes, Vibrio vulnificus, Bulkholderia cepacia, Photobacterium damselae damselae and Vibrio alginolyticus were isolated from cultured fish. Antibiotic resistance analyses showed that more than 50% of the bacteria were resistant to streptomycin, sulfamethoxazole, gentamycin, cephalothin, and ampicillin while they were very sensitive to florfenicol and chloramphenicol. The most prevalent resistance genes were found to be beta-lactam (blaTEM-OT3-4 ) and Tetracycline (tetB). This is the first study reporting isolation and antibiotic sensitivities of bacterial species in horse mackerel, which is expected to be a valuable source in predicting possible disease problems in horse mackerel aquaculture. [Copyright &y& Elsevier]

The diel horizontal migration (DHM) of fish between the inshore and offshore zones of the Římov Reservoir (Czech Republic, deep, stratified, meso-eutrophic) was investigated by a combination of horizontal and vertical hydroacoustic surveys at 3-h intervals over 48 h and day/night purse seining in August 2007. An overwhelming majority of fish were aggregated within the epilimnetic layer. Considering only the horizontal surveys, cyclic diel fish movements between inshore and offshore habitats were apparent, while the total fish biomass remained constant between day and night. A higher fish biomass was detected in the offshore zone during daytime by both hydroacoustics and purse seining. In contrast, a higher fish biomass was recorded at night in the inshore zone. Bream Abramis brama, roach Rutilus rutilus, and perch Perca fluviatilis dominated the daytime offshore fish assemblage whereas bleak Alburnus alburnus prevailed at night. Bream and roach decreased in abundance at night while perch completely disappeared from the offshore habitat. The diel differences in size distributions and direct catches suggested the population-wide horizontal offshore migration of bleak and inshore migration of all perch during dusk. On the other hand, partial inshore migration of bream and roach adults was observed during dusk (52 and 80%, respectively). The different proportions of offshore residents among species and size classes suggested that differences in size, and, therefore, predation vulnerability, contributed to the observed migration patterns. [ABSTRACT FROM AUTHOR]

This study analyzes the determinants of the choice of remuneration system and examines their influence on the economic performance of fisheries. The purse seine fisheries in Khanh Hoa province, Vietnam, are used as the study case, with data collected from 158 fishing households in 2005 and 2008. The principal-agent framework and the propensity score-matching technique are employed for the analysis. We demonstrate that insurance incentive-based problems are the rationale for the coexistence of share contracts and flat-wage contracts, even though share contracts bring greater economic benefit to both vessel owners and crew members. Crew members are found to be risk averse. Crew size and residence are important factors that influence the choice of contracts. Compared with flat-wage contracts, small share-contracted vessels are more efficient in managing the operating costs, while large ones are more efficient in yielding a high catch. [ABSTRACT FROM AUTHOR]

Abstract: Technical efficiency, uncertainties in data quality and natural fluctuations in fishing stocks constitute potential sources of fishing vessel inefficiency. Moreover, debate is on-going as to whether the skill of the fishermen (“skipper effect”) is an underlying actor in fishing efficiency. Therefore, this article monitors, calculates and quantifies the inefficiency caused by the “skipper effect”, if any, through the use of data envelopment analysis (DEA), with the aim of determining whether best practice target operational values in DEA, and their associated environmental impact reductions through LCA+DEA methodology, are achievable beyond the theoretical baseline they involve. A window analysis model is applied to the US menhaden fishery, a purse seining fleet with high homogeneity, since it is owned by the same company, with similar vessel and management characteristics. Results revealed relevant inefficiency levels in the four ports assessed, suggesting the existence of a “skipper effect” in all of them. Strong variances between vessels were identified, not only on an annual mean basis, but also per week of study. These variances could be attributed to random variation through time, if it were not for the fact that best performing vessels managed to repeatedly perform at high efficiency rates throughout the period. Moreover, standard deviations of low efficiency vessels were higher in all ports. Consequently, best performing targets calculated in LCA+DEA may be difficult to achieve in fleets where skipper skill strongly influences the sources of inefficiency. In these cases, the results suggest that resource minimization should be linked to specific measures to improve the individual skills of low performing vessels to attain best practice targets. [Copyright &y& Elsevier]

The article discusses the World Trade Organization Appellate Body's ruling in the 2012 case entitled United States--Measures Concerning the Importation, Marketing, and Sale of Tuna and Tuna Products which deals with tuna canning laws, international law, and dolphin-safe product labeling requirements under U.S. law. America's purse-seine fishing net regulations are examined, along with Mexican tuna imports and the Earth Island Institute environmental group.

This study provides a historical overview of the use of drifting fish aggregating devices (DFADs) in purse seine fisheries since the early 1990s, using global tuna fisheries datasets from the four tuna Regional Fisheries Management Organizations (RFMOs). Tropical tuna purse seine fisheries typically target large yellowfin (Thunnus albacares) and bigeye (Thunnus obesus) tunas on free-swimming schools and skipjack (Katsuwonus pelamis) and juveniles of yellowfin and bigeye associated with drifting objects. DFADs have enabled global skipjack catches to markedly increase, and have also introduced major scientific issues for all tuna-RFMOs. In particular, they have strongly modified the fishing strategies of purse seiners that fish on a combination of free-swimming and DFAD-associated schools. Consequently, the cumulated search time traditionally used to quantify nominal fishing effort to assess the status of tuna stocks is inconsistent and cannot be used to derive time series of abundance indices from catch-per-unit of-effort (CPUE). In addition, the lack of information available on the construction, deployment, and use of DFADs has prevented effective monitoring of the fishing pressure over the last two decades exerted by purse seine fleets using this fishing mode. Juveniles of tropical tunas represent a substantial proportion of purse seine catch on DFADs in the three oceans, which has raised particular concern for some bigeye stocks that have been subject to overfishing in the past. Catches of juvenile tunas by DFAD fishing may also result in a decrease in recruitment for fisheries that target adult tunas such as longliners. In addition, some demographic parameters of tunas and other species associated with DFADs may be affected by the resultant habitat modification arising from the widespread deployment of DFADs. Evidence in the literature and provided by the ratio-estimator method suggest that fishing DFAD-associated schools may result in about 100 000 t of bycatch and discards annually. In addition, there is further potential for ghost fishing related mortality of sensitive species such as marine turtles and pelagic sharks. In this context and following a precautionary approach, we finally discuss the increasing need for all tuna-RFMOs to reduce, or at least monitor and control, the use of DFADs to mitigate their adverse effects not only on yellowfin and bigeye stocks but also on open-ocean ecosystems. [ABSTRACT FROM AUTHOR]

Abstract: This paper discusses the development of ITQs in Norway. Even if some would deny that anything such exists, fisheries management in Norway has some unmistakable characteristics of an ITQ system. Both boatowners and policy makers have discovered the attractions of transferable quotas, the former as a means to increase their private profits, the latter as a vehicle to reduce fleet overcapacity. The slow evolution of transferability is mainly the result of ideological opposition and opposition to structural changes, the latter involving falling number of fishermen, changes in location of the fishing industry, and changed composition of the fishing fleet. The development of this system in the purse seine fleet and the fleet fishing for cod and similar species is traced. Then the concept of resource rent is discussed, as well as how it has become capitalized in quota values, which show up as a rise in value of long term assets of the fishing industry. [Copyright &y& Elsevier]

The empirical habitat suitability index (HSI) has been widely used to examine the habitat characteristics of terrestrial animals, though rarely used in highly migratory fish such as tuna. This study used the geographic information system technique to establish empirical models of HSI for yellowfin tuna (YFT) in the Western and Central Pacific Ocean (WCPO). Daily catch data from the Taiwanese purse seine fishery during 2003–2007 were aggregated monthly into sequential degrees before match processing the conducted data to obtain monthly remote-sensing data for multi-environmental factors, including sea surface temperature (SST), chlorophyll-a (chl-a), sea surface height (SSH) and sea surface salinity (SSS). According to the frequency distribution of each factor on which YFT were caught, this study transformed the values of the four factors into a suitability index (SI) ranging from low to high (0–1). These SI values were consequently combined into different empirical HSI models, and the optimum models were selected using the general linear model. The optimum empirical HSI for YFT in the study area was converted for SI (SST, SSH, chl-a and SSS) using the arithmetic mean model, of which the correct prediction rate was 71.9%. An agreement was present between the average HSI and total YFT catch. Furthermore, the high HSI area corresponds with the displacement of catch per unit effort (CPUE). [ABSTRACT FROM AUTHOR]

The marine fishery in Senegal, West Africa, is a major source of employment and food security. It currently faces the consequences of ecological degradation. This paper examines job satisfaction among small-scale purse seine fishers, who constitute one of the dominant fishing métiers in Senegal. The research sample consists of 80 purse seine fishers in three locations along the coast with varied degrees of urbanisation. The findings suggest that purse seine fishers are generally satisfied with the extent to which the fishery meets their Social Needs and Self-Actualisation. They are dissatisfied, however, with the degree to which Basic Needs are met, with the way in which Management is carried out, and-to a lesser extent-with the condition of the natural environment. However, the study shows significant differences between the more rural and urbanised settlements. These are most pronounced with regard to the willingness to change fishing type, move to another profession or advise a young person to enter fishing. [ABSTRACT FROM AUTHOR]

Tenningen, M., Vold, A., and Olsen, R. E. 2012. The response of herring to high crowding densities in purse-seines: survival and stress reaction. – ICES Journal of Marine Science, 69: .To study the effects of crowding in purse-seines on the survival and stress response of herring (Clupea harengus), large-scale field experiments were conducted in the North Sea during 2008 and 2009. The mortality was 28% at a crowding density of 221 kg m−3 and increased further with increasing density. Crowding densities <150 kg m−3 did not result in any additional mortality compared with the control group (0.9–2.0%). Smaller herring and herring with a lower condition factor were more vulnerable to the effects of crowding. Blood analyses showed a significant increase in cortisol, lactate, and blood ions in the crowded fish. Lactate returned to control levels 2 d post-stress, whereas cortisol and blood ion levels continued to increase during the 4- to 5-d monitoring period. Furthermore, plasma glucose appeared to be substantially reduced at the end of the trial, indicating that the herring were incapable of restoring homeostasis and were approaching energy exhaustion. These results provide important information about the crowding densities that can be tolerated in the purse-seine fisheries for herring and will benefit future development of guidelines for purse-seine slipping operations. [ABSTRACT FROM PUBLISHER]

Amandè, M. J., Chassot, E., Chavance, P., Murua, H., Delgado de Molina, A., and Bez, N. 2012. Precision in bycatch estimates: the case of tuna purse-seine fisheries in the Indian Ocean. – ICES Journal of Marine Science, 69: .Estimating bycatch, i.e. the incidental catch of non-target marine animals and undersized individuals of target species, by raising observer data to the whole fishery is routine practice. The annual bycatch of the European tropical tuna purse-seine fishery over the period 2003–2009 was estimated at 11 590 t [95% confidence interval: (8165–15 818 t)], corresponding to 4.7% of the tuna landings. An analysis of the variability in the precision of this estimate, based on generalized linear models and Monte Carlo simulations, showed that the current sampling coverage of the tropical tuna fishery observer programme, which is 4.6% of the fishing trips, resulted in large uncertainties in bycatch estimates by species, i.e. none of the estimates have a relative root mean square error smaller than 50%. Although the overall magnitude of bycatch of the fishery appeared to be small, the current sampling coverage was insufficient to give any reliable estimate for low-occurring species, such as marine turtles, some oceanic pelagic sharks, and some billfishes. Increasing the sampling coverage would likely improve bycatch estimates. Simulation outputs were produced to help define (i) trade-offs between the priority species to be monitored, (ii) the estimation precision, (iii) expected accuracy, and (iv) the associated sampling costs. [ABSTRACT FROM PUBLISHER]

Abstract: The aim of this study was to test the selectivity of a trawl main body, especially for small fish, during night sampling. The tested trawl had a mesh size of 80/40/20mm in the main body, a mouth opening of approximately 100m2, and a length of 48m and was originally designed for sampling vendace, Coregonus albula L. Trawl selectivity was determined by comparing the catch using this gear with that from a purse seine net (mesh size 6–10mm, length 120m, height 12m) at the same sites and time. The size distributions of the total catch and densities of three dominant species (common bream, Abramis brama (L.), roach, Rutilus rutilus (L.) and bleak, Alburnus alburnus (L.)) were compared between the two types of gear. Densities of these species were divided into size groups before comparison: (i) small fish (60–120mm, standard length SL); (ii) middle-sized fish (125–180mm SL); and (iii) large fish (>180mm SL), which included only roach and bream. Significant differences in the fish density between the trawl and purse seine nets were found. Generally, the densities in all size categories of bleak and small roach were underestimated in trawl catches, whereas the densities of middle- and large-sized bream were underestimated in the purse seine catch. We conclude that both types of gear are size selective – small fish escaped through the mesh of the trawl main body, whereas larger bream were able to escape from the purse seine before closing. The trawl with the given mesh sizes is recommended for quantitative sampling only of fish larger than 180mm (SL) under low light-intensity conditions. [Copyright &y& Elsevier]

Abstract: Two techniques, the conventional purse seine method and a novel method using vertical hydroacoustic surveys at fixed positions, were applied simultaneously in the Gambia River estuary to sample a fish population. Environmental parameters were measured simultaneously. Four surveys were performed during different hydrological seasons to reflect the main sources of variation in the environmental conditions of the estuary. A total of 153 samples resulted from these surveys. To identify the environmental conditions in which the two methods yield similar pictures of the fish population, a regression tree was constructed in which the dependent variable was the difference between the standardised values of the catches from the purse seine and the estimated biomass from the acoustic samples. A highly significant correlation was found between the two approaches using a set of data (128 samples) that excluded the samples with specific environmental conditions (downstream samples with high transparency, and upstream ones with high transparency, high depth and high temperature). We conclude that, except under these specific environmental conditions, vertical hydroacoustic samples recorded at a fixed station can serve as a proxy of the catches from a purse seine and can allow the monitoring of fish biomass in estuaries without damaging the environment. [Copyright &y& Elsevier]

Wahoo (Acanthocybium solandri) is distributed in all tropical and subtropical oceans and caught incidentally by the tuna purse-seine fishery in the Eastern Pacific Ocean (EPO). Generalized additive models (GAM) and boosted regression trees (BRT) were used to analyze relationships between presence of wahoo in logbook data from the Mexican tuna purse-seine fishery with environment, geographic area and set type (unassociated, associated with dolphins or floating objects set). Model performance was evaluated using changes in deviance in the fitted models and the area under the receiver operating characteristic curve (ROC). Results indicate little difference between the performance of GAM and BRT models. Both methods were consistent with predictions of presence of wahoo with respect to the variables used. Set type was the single most important predictor of variation in presence of wahoo, with highest probability of incidental catch in sets made on floating objects. With respect to environmental factors, sea surface temperature (20–25°C) and chlorophyll-a concentration (<2mgm−3) determined the highest probability of incidental catch of wahoo. The coast of Baja California Sur, Mexico and south of the equator were predicted to have a high probability of incidental catch of wahoo. [Copyright &y& Elsevier]

I analyze drivers of investment in a fishery with tradable quotas. Theory predicts that tradable quotas increase efficiency because efficient firms buy quotas from less efficient firms. I identify what drives investment, using data on Norwegian purse seiners. Results show that while the basic economic investment model explains investment within firms, it does not explain differences between firms. These differences are explained by other firm-specific factors such as geographical location, whether it is a family firm, and prices paid for quotas. Consequently, investment strategies are not necessarily driven by efficiency considerations, and quota trade may not increase allocative efficiency. [ABSTRACT FROM AUTHOR]

An ecosystem approach to fisheries management is a widely recognized goal, but describing and measuring the effects of a fishery on an ecosystem is difficult. Ecological information on the entire catch (all animals removed, whether retained or discarded) of both species targeted by the fishery and nontarget species (i.e., bycatch) is required. We used data from the well-documented purse-seine fishery for tunas (Thunnus albacares, T. obesus, and Katsuwonus pelamis) in the eastern tropical Pacific Ocean to examine the fishery's ecological effects. Purse-seine fishing in the eastern tropical Pacific is conducted in 3 ways that differ in the amount and composition of target species and bycatch. The choice of method depends on whether the tunas are swimming alone (unassociated sets), associated with dolphins (dolphin sets), or associated with floating objects (floating-object sets). Among the fishing methods, we compared catch on the basis of weight, number of individuals, trophic level, replacement time, and diversity. Floating-object sets removed 2-3 times as much biomass as the other 2 methods, depending on how removal was measured. Results of previous studies suggest the ecological effects of floating-object sets are thousands of times greater than the effects of other methods, but these results were derived from only numbers of discarded animals. Management of the fishery has been driven to a substantial extent by a focus on reducing bycatch, although discards are currently 4.8% of total catch by weight, compared with global averages of 7.5% for tuna longline fishing and 30.0% for midwater trawling. An ecosystem approach to fisheries management requires that ecological effects of fishing on all animals removed by a fishery, not just bycatch or discarded catch, be measured with a variety of metrics. [ABSTRACT FROM AUTHOR]

Abstract: Developing socioeconomic indicators for ecosystem-based fisheries management is particularly important. This is because socioeconomic factors have direct effects on ecosystems, and ecosystems have direct effects on socioeconomic factors. Therefore, it is imperative that socioeconomic indicators are developed and evaluated in order to predict changes in ecosystems and to provide advice for effective fisheries management. In this study, socioeconomic indicators have been developed to be combined with biological and ecological indicators, in order to conduct the ecosystem-based fisheries assessment. In terms of socioeconomic indicators, five socioeconomic criteria were considered as important attributes of socioeconomic changes. These were economic production, business conditions, levels of income, the state of the market, and levels of employment. In order to establish reference points for the evaluation of indicators, target reference points and limit reference points were set through a comparison with other industries or other fisheries rather than by using the Traffic Light System (TLS) method, which has been used in many previous studies. In addition, on the basis of the application of developed indicators and reference points to the Korean large purse seine fishery, the socioeconomic conditions of the fishery and the usefulness of the indicators were evaluated and management implications were discussed. [Copyright &y& Elsevier]

Abstract: In this study the microbiota of Atlantic mackerel (Scomber scombrus) collected by a commercial purse seiner was examined. Fish were collected directly from the purse seine and from the Refrigerated Sea Water (RSW) transport tank after loading. The culturable microbiota and Specific Spoilage Bacteria (SSB) were quantified on Iron Agar Lyngby (IAL) and identified using commercially available Biochemical API® kits on pure cultured isolates. These kits showed to be sub-optimal in characterising the isolates, since only half of the strains were identified. The same isolates were also identified by a nucleic acid based PCR-DGGE approach, and only half of the sequences gave the same results as the API®. Characterisation by PCR-DGGE was also performed on bacterial DNA from IAL plates (bulk cell samples) and on samples where the bacterial DNA was extracted directly from fish material without any cultivation (direct DNA samples). The microbiota of Atlantic mackerel was dominated by members of the Gram-negative genera as Psychrobacter sp., Proteus sp., Photobacterium sp., Vibrio sp., Shewanella sp., Synechococcus sp., Oceanisphaerae sp., Bizonia sp., Pseudoalteromonas sp., and members of Flavobacteriaceae. Gram-positive bacteria in the genera Vagococcus sp., Bacillus sp., Mycobacterium sp., Staphylococcus sp., Mycoplasma sp. and Clostridia sp. were also found. Examination by PCR-DGGE and sequencing of the bulk cell pellet after cultivation on IAL, gave a higher number of taxa as compared to extraction and examination of bacterial DNA from fish materials without prior cultivation. This shows the benefit of combining both culture dependent and culture independent methods, when studying the microbiota of marine fish. Several Vibrio spp. were found only in gut samples collected from the purse seine, but in all samples including the skin and the gills collected from the RSW tank, indicating microbial contamination by faecal bacteria from the fish under these transport conditions. [Copyright &y& Elsevier]

Abstract: Overexploitation of bycatch and target species in marine capture fisheries is the most widespread and direct driver of change and loss of global marine biodiversity. Bycatch in purse seine and pelagic longline tuna fisheries, the two primary gear types for catching tunas, is a primary mortality source of some populations of seabirds, sea turtles, marine mammals and sharks. Bycatch of juvenile tunas and unmarketable species and sizes of other fish in purse seine fisheries, and juvenile swordfish in longline fisheries, contributes to the overexploitation of some stocks, and is an allocation issue. There has been substantial progress in identifying gear technology solutions to seabird and sea turtle bycatch on longlines and to direct dolphin mortality in purse seines. Given sufficient investment, gear technology solutions are probably feasible for the remaining bycatch problems. More comprehensive consideration across species groups is needed to identify conflicts as well as mutual benefits from mitigation methods. Fishery-specific bycatch assessments are necessary to determine the efficacy, economic viability, practicality and safety of alternative mitigation methods. While support for gear technology research and development has generally been strong, political will to achieve broad uptake of best practices has been lacking. The five Regional Fisheries Management Organizations have achieved mixed progress mitigating bycatch. Large gaps remain in both knowledge of ecological risks and governance of bycatch. Most binding conservation and management measures fall short of gear technology best practice. A lack of performance standards, in combination with an inadequate observer coverage for all but large Pacific purse seiners, and incomplete data collection, hinders assessing measures'' efficacy. Compliance is probably low due to inadequate surveillance and enforcement. Illegal, unreported and unregulated tuna fishing hampers governance efforts. Replacing consensus-based decision-making and eliminating opt-out provisions would help. Instituting rights-based management measures could elicit improved bycatch mitigation practices. While gradual improvements in an international governance of bycatch can be expected, market-based mechanisms, including retailers and their suppliers working with fisheries to gradually improve practices and governance, promise to be expeditious and effective. [Copyright &y& Elsevier]

Purpose: The purpose of this study was to evaluate the environmental impacts linked to fish extraction on a temporal basis, in order to analyze the effect that stock abundance variations may have on reporting environmental burdens. Inventory data for the North-East Atlantic Mackerel (NEAM) fishing season were collected over an 8-year period and used to carry out a life cycle assessment (LCA). The selected fishery corresponds to the Basque coastal purse seining fleet. Materials and methods: The functional unit (FU) was set as 1 t of landed round fish in a Basque port during the NEAM fishing season for each of the selected years. The selected data for the life cycle inventory were gathered from personal communication from ship owners and from a fish first sale register in the Basque Country. A series of fishery-specific impact categories and indicators were included in the evaluation together with conventional impact categories. Results and discussion: Conventional LCA impact categories showed that the environmental impact is dominated by the energy use in the fishery, despite of the low fuel effort identified with respect to other purse-seining fisheries. Nevertheless, strong differences were identified between annual environmental impacts, attributed mainly to remarkable variations in NEAM stock abundance from 1 year to another, whereas the fishing effort remained relatively stable throughout the assessed years. Fishery-specific categories, such as the discard rate or seafloor impact showed reduced impacts of this fishery respect to other small pelagic fish fisheries. Finally, the fishery in balance (FiB) index identified the evolution of NEAM stock abundance for this particular fishery. Conclusion: To our knowledge, this is the first fishery LCA study in which there is sufficient inventory data in order to conduct the methodology throughout a wide period of time. The outstanding variance in environmental impacts from one season to another evidences the need to expand fishery LCAs in time, in order to attain a more integrated perspective of the environmental performance of a certain fishery or species. The extension of LCA inventories in the timeline may be an important improvement for activities that rely entirely on the extraction of organisms from wild ecosystems. For instance, future research will have to determine the importance of increasing the timeline in fishery LCAs for species that do not show large stock abundance variations through time, unlike NEAM. [ABSTRACT FROM AUTHOR]

This work is proposing a dynamic model governing the evolution with respect to time of the sardine (Sardina pilchardus) stock in the Atlantic coast between Cantin Cape and Blanc Cape in the North West Africa, which is harvested by two different fishing fleets. We assume that the sardine stock is distributed on two closed zones and targeted by a composite fleet: The Moroccan purse seiners which can move between the fishing regions and a fleet of deepsea trawlers composed mainly of foreign vessels and operating in the southern zone. The model is a set of 5 Ordinary Differential Equations (ODE) with two components: a stock component which describes the sardine evolutions in its 2 zones of distribution, and a component governing the dynamics of the fishing efforts. By using some aggregation methods, we reduce the system to a set of 4 ODE, and then we study analytically the existence and the asymptotic stability of the equilibrium points. The parameters of the stock dynamics and harvest are then estimated using models fitting techniques based on a set of available data. The conditions leading to sustainable fisheries are then simulated. Interpretations of our results can be used by the authority responsible of fishery management, as general recommendations for a better management of Moroccan fisheries. [Copyright &y& Elsevier]

Through the mid 1990's, the bait purse-seine fishery for Atlantic menhaden, Brevoortia tyrannus, in the Virginia portion of Chesapeake Bay was essentially undocumented. Beginning in 1995, captains of Virginia bait vessels maintained deck logs of their daily fishing activities; concurrently, we sampled the bait landings for size and age composition of the catch. Herein, we summarize 15 years (1995-2009) of data from the deck logbooks, including information on total bait landings by purse seine, proportion of fishing to non-fishing days, proportion of purse-seine sets assisted by spotter pilots, nominal fishing effort, median catches, and temporal and areal trends in catch. Age and size composition of the catch are described, as well as vessel and gear characteristics and disposition of the catch. [ABSTRACT FROM AUTHOR]

Abstract: Tuna purse seining in the Pacific Islands region is the world’s largest tuna fishery. Currently some organizations are publicising the desirability of replacing at least some of the purse seining with pole-and-line fishing—a technique which requires significant quantities of live baitfish. This research was undertaken to determine the quantity of baitfish required to replace purse seining. It is estimated that to catch a million tonnes of tuna annually in the Pacific Islands region (i.e. replace the purse seine fishery) would require about 31,250t of baitfish per year. Historical catches of baitfish suggest that catches this large may not be possible. There is also some question of the practicality and desirability of a substantial increase in baitfish harvesting in the region. [ABSTRACT FROM AUTHOR]

The spatial behavior of numerous fishing fleets is nowadays well documented thanks to satellite Vessel Monitoring Systems (VMS). Vessel positions are recorded on a frequent and regular basis which opens promising perspectives for improving fishing effort estimation and management. However, no specific information is provided on whether the vessel is fishing or not. To answer that question, existing works on VMS data usually apply simple criteria (e.g. threshold on speed). Those simple criteria generally focus in detecting true positives (a true fishing set detected as a fishing set); conversely, estimation errors are given no attention. For our case study, the Peruvian anchovy fishery, those criteria overestimate the total number of fishing sets by 182%. To overcome this problem an artificial neural network (ANN) approach is presented here. In order to set both the optimal parameterization and use “rules” for this ANN, we perform an extensive sensitivity analysis on the optimization of (1) the internal structure and training algorithm of the ANN and (2) the “rules” used for choosing both the relative size and the composition of the databases (DBs) used for training and inferring with the ANN. The “optimized” ANN greatly improves the estimates of the number and location of fishing events. For our case study, ANN reduces the total estimation error on the number of fishing sets to 1% (in average) and obtains 76% of true positives. This spatially explicit information on effort, provided with error estimation, should greatly reduce misleading interpretations of catch per unit effort and thus significantly improve the adaptive management of fisheries. While fitted on Peruvian anchovy fishery data, this type of neural network approach has wider potential and could be implemented in any fishery relying on both VMS and at-sea observer data. In order to increase the accuracy of the ANN results, we also suggest some criteria for improving sampling design by at-sea observers and VMS data. [Copyright &y& Elsevier]

Abstract: This paper investigates the productivity of marine fisheries on the east and west coasts of Peninsular Malaysia for the period 1990–2005. Based on the data for landings and effort, weighted catch per unit of effort (CPUE) is computed for the trawl, purse seine and traditional fleets. The weighted CPUE differentiates the quality or composition of catch through weighting of the species mix in the catch by the share of total revenue of each species. Similarly, the various inputs that constitute fishing effort are weighted by their respective cost shares. The ratio of the Tornqvist chain catch and effort indices was used to measure intertemporal productivity changes in the respective fisheries. The results showed that the weighted CPUE was the highest for purse seine on the east and west coasts of Peninsular Malaysia. However, the productivity of purse seine fleet has not been tremendously increased over time. The productivities of trawl and traditional fleets on the east and west coasts were low. Restricting fishing effort through vessel limitation programs is viewed as a possible way of raising the productivities of these fleets. In addition, productivity increases can be achieved by enhancement of the resource stocks such as through the construction of artificial reefs. [Copyright &y& Elsevier]

The impact of fisheries within a Natura 2000 area in western Greece was assessed over a 12-month period in 2007. The estimated total biomass removed annually by 307 fishing boats averaged 3503.5 t. Purse seiners, beach seiners and trawlers took 70% of the total landings. Purse seiners, contributing 3% of the total fishing fleet, were responsible for 33% of total biomass removed. Beach and purse seiners primarily caught small pelagic species, whereas trawlers and trammel netters mostly demersal species. A mismatch was found between the Common Fisheries Register (CFR) and an in situ assessment of the active fishing fleet; the number of industrial fishing boats exceeded those registered in CFR for the three administrative ports involved, and a large proportion of the CFR netters were small and effectively inactive. Fishery management measures for the recovery of an ecosystem considerably damaged by overfishing are proposed. [ABSTRACT FROM AUTHOR]

Length, life history and ecological characteristics of landed fish communities were studied over a 10-year period to test theories of fishing disturbance during a time of increased gear and closure management in heavily utilised fisheries. It was predicted that with greater management restrictions: (1) the earliest and fastest responses in the fishery will be seen in those species with faster turnovers, or relatively lower vulnerabilities to fishing; (2) the fishery would transition to a landed catch with higher mean trophic levels, and greater mean body lengths. In addition, the removal of a non-selective, small-mesh seine nets should benefit the catch of gears that previously had the greatest species selectivity overlap with the seine net. Many predictions were supported, although maximum lengths and lengths at maturity responded more rapidly than anticipated. The response to eliminating the non-selective seine net was a more rapid increase in sizes caught by gears with a larger overlap in size (hook and lines) than species selectivity (gill nets). The simultaneous comparison of management systems over time indicates that open-access fishing grounds can benefit from restrictions imposed in adjacent fishing grounds. The study indicated that multi-species coral reef fisheries management objectives of maximising yields, as well as maintaining the fish community's life-history diversity, require management trade-offs that balance local socio-economic and biodiversity needs. [ABSTRACT FROM AUTHOR]

Ecological risk assessment is a useful methodology for assisting the management of fisheries from an ecosystem perspective. Atlantic tuna fisheries, managed by the International Commission for the Conservation of Atlantic Tunas (ICCAT), are economically important and interact with several bycatch species. In spite of these interactions, no comprehensive ecological risk assessment has been conducted for bycatch species caught in ICCAT fisheries. In this paper, we followed a two stage approach with the objective of assessing the relative risk of species being negatively impacted by Atlantic tuna fisheries. An analysis of the ICCAT bycatch species list (which includes all species reported to have interacted with different tuna fishing gears operating in the Atlantic) revealed that most of these species are caught in longline fisheries, followed by gillnets and purse seines. According to the IUCN red list, 7 species of the ICCAT bycatch list (3 coastal sharks, 3 sea turtles and one seabird) are categorized as critically endangered. In our study, and based on their life history characteristics, marine mammals and coastal sharks caught in ICCAT fisheries showed the highest intrinsic vulnerability values. A productivity susceptibility analysis for the European Union (EU) tropical tuna purse seine fleet and the United States (US) pelagic longline fleet revealed two groups with high relative risk scores. The first one included pelagic and coastal sharks, characterized by relatively low productivities, and the second one included teleosts, characterized by higher productivities but high susceptibility to purse seine and longline gears. Some alternative approaches to conduct productivity susceptibility analyses in the context of ecological risk assessments are discussed. [ABSTRACT FROM PUBLISHER]

Bycatch of several groups of species and their characteristics are presented for the period 2003 to 2007 for the European purse seine tuna fishery operating in the Atlantic Ocean. Data were collected through French and Spanish observer programmes and represented a total of 27 trips corresponding to 2.9% coverage. Bycatch is defined as non-targeted species and small or damaged target species. Bycatch species composition, main species length, sex ratio and the fate of the most common species are presented first. Stratified ratios relative to landings of major commercial tunas were then used to estimate the total bycatch; these ratios were considered the most appropriate variable for extrapolation. Stratification was based on the fishing mode (free school vs. floating object), season (quarters) and spatial areas. The annual average bycatch was estimated at about 6400 t, corresponding to a mean annual value of 80.8 t per 1000 t of tuna landed or 7.5% of the total catch. Tunas represent 83% (67.2 t/1000 t) of the total bycatch, followed by other bony fishes (10%, 7.8 t/1000 t), billfishes (5%, 4.0 t/1000 t), sharks (1%, 0.9 t/1000 t) and rays (1%, 0.9 t/1000 t). Based on estimates of the annual bycatch, 16% was kept on board and sold in local markets. [ABSTRACT FROM PUBLISHER]

Abstract: On 1 December 2007, eight ‘Small Island Developing States’ in the Western and Central Pacific Ocean implemented a management regime restricting the total number of days fished by tuna purse seine vessels within their waters, commonly referred to as the Vessel Day Scheme (VDS). The VDS is seen as one component of management arrangements to reduce fishing mortality on bigeye and yellowfin tuna, constrain fishing effort, and increase the rate of return from access fees by Distant Water Fishing Nations. [Copyright &y& Elsevier]

Abstract: Mesoscale physical features as fronts and eddies appear to play a key role in the dynamics of marine communities. In the Indian Ocean, the Mozambique Channel (MC) is a natural laboratory to investigate mesoscale eddies (100–300km in diameter); indeed, four to seven eddies per year are know to transit through the Channel, from North to South. We studied the structuring role of the mesoscale eddies on spatial dynamics and foraging strategy of top predators using seabirds and tuna as examples. Emphasis was on the central part of the MC (16–24°S) where eddy activity is most developed. We integrated three main categories of information: (i) satellite altimetry for sea-level anomaly (SLA) and geostrophic current, remotely-sensed surface temperature (SST) and SeaWiFS data for chlorophyll concentration (CC); (ii) individual tracking of Great Frigatebirds (Fregata minor) to characterize foraging areas; and (iii) detailed catch statistics from purse-seine fisheries to describe distribution of tuna schools. Generalized Additive Models were applied to quantify the relative influence of mesoscale descriptors, SST and CC on foraging behaviour of Great Frigatebirds and location of purse-seine sets. Our results show that seabirds are more closely tied to mesoscale eddies compared to tuna. We underline the role of eddy boundaries on the response of frigatebirds and tuna. Good foraging conditions are promoted along the edge of eddies as a result of the interplay of the maturation process from cyclonic eddies and the concentration process by eddy interactions. A decrease in the number or intensity of eddies in the MC, as observed during strong El Niño events, could potentially affect the eddy-related ecosystem with putative negative repercussions on central-place foragers such as Great Frigatebirds. We discuss the importance of a better understanding of the “eddy system”, in marine conservation and tuna fisheries management in the Mozambique Channel. [Copyright &y& Elsevier]

Abstract: Great Frigatebirds (Fregata minor) are large tropical seabirds that rely primarily on sub-surface predators such as tunas or cetaceans to capture their prey. We studied the foraging movements of 14 Great Frigatebirds breeding on Aldabra Island (9.4°S, 46.4°E), the largest colony in the Indian Ocean. This colony is located at more than 500km from the main fishing grounds of a very important industrial purse-seine fishery targeting surface-dwelling tunas. Despite their slow flight speeds (16kmh−1), frigatebirds are able to forage at more than 1000km from the colonies when breeding, using 2500–4750km long foraging loops over oceanic waters. All trips were directed to the north of the island up to the equator. Foraging bouts, indicated by reduced flight speeds, were rare and located throughout the trips. Foraging spots tended to be more frequent on higher surface chlorophyll concentration and in association with some cyclonic vortices. However, mesoscale activity is relatively weak between Aldabra and the equator and the chlorophyll variability is mostly the result of wind-mixing processes during the southwest monsoon. These results suggest that frigatebirds forage for widely distributed resources to the north of Aldabra. The northernmost foraging bouts were located in the vicinity of the purse-seine fishing grounds, but without a significant overlap between frigatebirds and tuna fleets. The results of the study are compared with those from another population at Europa Island (22.3°S, 40.3°E) where birds were foraging on predictable features, the edge of cyclonic eddies that are marked in the Mozambique Channel. We discuss the consequences of the reliance of populations on contrasted oceanographic conditions on foraging strategies and on the evolution of life histories in these long-lived animals in a changing climate, as well as the possible effects of overfishing on frigatebird populations. [Copyright &y& Elsevier]

Abstract: Evaluating the impacts of climate and fishing on oceanic ecosystems requires an improved understanding of the trophodynamics of pelagic food webs. Our approach was to examine broad-scale spatial relationships among the stable N isotope values of copepods and yellowfin tuna (Thunnus albacares), and to quantify yellowfin tuna trophic status in the food web based on stable-isotope and stomach-contents analyses. Using a generalized additive model fitted to abundance-weighted-average δ15N values of several omnivorous copepod species, we examined isotopic spatial relationships among yellowfin tuna and copepods. We found a broad-scale, uniform gradient in δ15N values of copepods increasing from south to north in a region encompassing the eastern Pacific warm pool and parts of several current systems. Over the same region, a similar trend was observed for the δ15N values in the white muscle of yellowfin tuna caught by the purse-seine fishery, implying limited movement behavior. Assuming the omnivorous copepods represent a proxy for the δ15N values at the base of the food web, the isotopic difference between these two taxa, “Δ YFT-COP,” was interpreted as a trophic-position offset. Yellowfin tuna trophic-position estimates based on their bulk δ15N values were not significantly different than independent estimates based on stomach contents, but are sensitive to errors in the trophic enrichment factor and the trophic position of copepods. An apparent inshore–offshore, east to west gradient in yellowfin tuna trophic position was corroborated using compound-specific isotope analysis of amino acids conducted on a subset of samples. The gradient was not explained by the distribution of yellowfin tuna of different sizes, by seasonal variability at the base of the food web, or by known ambit distances (i.e. movements). Yellowfin tuna stomach contents did not show a regular inshore–offshore gradient in trophic position during 2003–2005, but the trophic-position estimates based on both methods had similar scales of variability. We conclude that trophic status of yellowfin tuna increased significantly from east to west over the study area based on the spatial pattern of Δ YFT-COP values and the difference between the δ15N values of glutamic acid and glycine, “trophic” and “source” amino acids, respectively. These results provide improved depictions of trophic links and biomass flows for food-web models, effective tools to evaluate climate and fishing effects on exploited ecosystems. [Copyright &y& Elsevier]

Abstract: Commercial fisheries are heavily dependent upon the combustion of fossil fuels and as such contribute to increased atmospheric concentrations of greenhouse gases and the concomitant impact on the world''s climate. The fuel use and greenhouse gas intensity of a fishery is a function of several variables. One that has not been previously investigated is the role of fisheries management. Using historical gear-specific fuel use and landings data, we employ scenarios to examine the potential impact that recent changes in the management of the New England fishery for Atlantic herring (Clupea harengus) may have on fishery-related fuel use and greenhouse gas emissions. Specifically, we consider the direct effect of the seasonal ban of midwater trawling in favor of purse seine and fixed gears within Atlantic herring fishing Area 1A. We also evaluate the indirect effect of reductions to the Area 1A total allowable catch of Atlantic herring on the regional supply of bait and the resulting potential need to import bait herring from Canada. Our results indicate that because of the five-fold lower fuel intensity of purse seining, relative to midwater trawling (21 L/ton versus 108-118 L/ton), the seasonal ban on midwater trawling has the potential to markedly reduce overall fuel use and greenhouse gas emissions associated with the herring fishery. These results indicate that management decisions can strongly influence energy demands and resulting greenhouse gas emissions of fisheries. We urge those involved with fisheries management to take this into account when developing policy and management measures. [Copyright &y& Elsevier]

The article offers information on tuna farming. It is stated that floating cages are located on the coasts of various Mediterranean countries, with small tunas provided mainly by the purse seine fishery to stock the cages. The study was promoted by the increase in off-shore farming activities and the use of technological systems to monitor aquaculture sites.

Abstract: Pelagic fish stocks in the Java Sea have been exploited intensively since the beginning of the 1970s. However, due to the effect of increased fishing power of the fleets and the changing nature of spatial and temporal distribution of the fishing effort, assessment of stock trends based on commercial data of catch and effort requires the standardization of both effort and catch data. Here we present the first attempt to reconstruct a standardized time series of commercial catch per unit of effort (CPUE) for the main pelagic species exploited by the purse seine fleet in the Java Sea. The results showed that all the stocks analysed have largely declined since the beginning of the 1990s. For bigeye scad, Indian mackerel and sardine, current estimates are only between 3 and 19% of the maximum observed value while round scads and spotted sardine biomass estimates lie between 18 and 34%. However, our assumptions about the effect of lamp power and level of creeping and the fact that the influence of fish density on catchability and the effect of targeting were not taken into account thus observed decline is a rather conservative estimate of the real decline of the stocks. If effective management actions are not put in place as a matter of urgency in the Java Sea for small pelagic fisheries, one runs the risk of adding those species to the long list of overexploited stocks of the world oceans. [Copyright &y& Elsevier]

In 1963, the leading fisheries targeting Atlantic bluefin tuna ( Thunnus thynnus) in the Norwegian Sea and North Sea suddenly collapsed without any warning. Little is known about this collapse and several hypotheses have been put forward, such as changes in migratory routes, recruitment failure or eradication of a sub-population: all of these hypotheses could result from natural causes and/or from overfishing. To help explain this mysterious event, an original data set of the main bluefin tuna fisheries of the 20th century, including total catch and size composition of the catch, has been compiled and analysed. The results reveal a strong and unambiguous link between the Nordic purse seine and Spanish trap fisheries during the 1950s and 1960s. However, this link vanished during the 1970s. In addition, the North-west Atlantic and Mediterranean trap fisheries appeared also to be partially connected to the Nordic fisheries. During the 1950s and 1960s, the main migration routes of bluefin tuna were probably from the Mediterranean spawning grounds and from the West Atlantic coasts to the Norwegian coast and North Sea, which were probably a key feeding ground at that time. The analyses also lead to the conclusion that interactions between environmental, trophic and fishing processes have probably affected bluefin tuna migration patterns which would have finally caused the Nordic fisheries collapse. This retrospective analysis finally leads to an original – albeit more speculative – hypothesis concerning Atlantic bluefin tuna population structure, therein conjectured as an assemblage of at least three sub-populations. [ABSTRACT FROM AUTHOR]

Fisheries bycatches and discards constitute a significant problem in many fisheries worldwide. Unlike the pelagic purse-seine, the demersal purse seine usually targets high commercial value demersal species such as sea breams (e.g., Diplodus spp., Pagellus spp., Sparus aurata) and the European sea bass (Dicentrarchus labrax), while discards consist mainly of pelagic species and juveniles of the above mentioned species. In order to evaluate the efficiency of a selectivity device in reducing bycatch and consequently of discards in a demersal purse seine fishery, experimental deployments were carried out. The bycatch reducing device (BRD) consisted in the use of a panel of diamond-shaped mesh netting of 70 mm stretched mesh in the posterior part of the purse seine. Data from 61 experimental fishing trials allowed the evaluation of discards, with Scomber japonicus, Boops boops, Sardina pilchardus, Diplodus bellottii and Belone belone being the main discarded species. The mean discard ratio per set was 0.49 (± 0.30 standard deviation). The causes for discarding were also identified, with low commercial value being the most important reason. The results of the trials with BRD, were promising, with an average of 49% (± 24%) of the fish escaping per set, especially from those species that are most discarded. Overall, the use of this method for reducing discards can be considered positive for the following reasons: there is no need for structural modification of the fishing gear, the BRD is easy to deploy, and it is efficient in terms of species, sizes and quantities of fish that manage to escape. It therefore has significant benefits for the demersal purse seine fishery and possibly for other "métiers" as well. [ABSTRACT FROM AUTHOR]

Abstract: In the eastern Pacific Ocean (EPO), dolphinfish (Coryphaena spp.) are caught incidentally by the tuna purse-seine fishery; therefore, the records of this fishery are a good source of information to analyze the distribution of dolphinfish. To determine the spatiotemporal distribution of dolphinfish and catch variability in the three types of tuna-fishing sets (on schools associated with dolphins or with floating objects, or on unassociated schools), statistical analyses were made of the 1998–2005 records taken by scientific observers on board tuna-fishing vessels. The incidental catch did not show a well-defined annual or seasonal distribution pattern. Two high catch areas were observed, the first located in Mexican offshore waters (15–25°N), with 15% of the total catch, and the second located in offshore waters of the central EPO (0–10°N), with almost 60% of the total catch. The incidental catch was significantly different among years and seasons (H 7,780 =54.6, p <0.05 for years, and H 3,780 =42.7, p <0.05 for seasons), the greatest catch being recorded during 1999 and the first two quarters, respectively. Sets on floating objects recorded most of the incidental catch of dolphinfish, followed by unassociated sets, while dolphin-associated sets recorded the lowest catch. Almost 80% of the total catch was fished in waters with sea-surface temperatures between 25°C and 28°C. The mean size of dolphinfish was significantly different (H 2,777 =12.8, p <0.05) by set type, but the smallest specimens caught were associated with floating objects. Among sets associated with floating objects, the incidental catch of dolphinfish was greatest in sets on logs, branches, etc. (PALO sets), though those on FADs (fish-aggregating devices) were the most numerous in the central EPO. [Copyright &y& Elsevier]

Lennert-Cody, C. E., Roberts, J. J., and Stephenson, R. J. 2008. Effects of gear characteristics on the presence of bigeye tuna (Thunnus obesus) in the catches of the purse-seine fishery of the eastern Pacific Ocean. – ICES Journal of Marine Science, 65: 970–978.Overfishing of bigeye tuna in the eastern Pacific Ocean has motivated a search for a practical means of reducing the catch of bigeye tuna in mixed species aggregations. To explore the effects of gear characteristics on the catch of bigeye tuna, a classification algorithm for the presence/absence of bigeye tuna catch in purse-seine sets on floating objects is developed, using the tree-based method, random forests. Although the location of the set was the strongest determinant of bigeye tuna catch with these data, bigeye tuna in some areas were more likely to be caught on floating objects with greater underwater depths and with deeper purse-seines. Misclassified sets that caught bigeye tuna were concentrated within certain vessels, suggesting the existence of additional vessel effects. Results indicate that fishers may avoid catching bigeye tuna in some areas by changing the depth of the material hanging from the floating object and the actual fishing depth of the purse-seine, or by moving to other fishing areas. Nonetheless, given the complexity of configuring a purse-seine, and the difficulties associated with monitoring compliance with gear regulations, fishery-wide gear restrictions would be problematic. [ABSTRACT FROM PUBLISHER]

Prescribed or natural drawdowns occur frequently in reservoirs but their effects on fish populations have been barely studied. As a consequence of a severe drought and the need to optimize water quality, a partial drawdown was prescribed in autumn 2005 to a eutrophic reservoir that provides water supply to a large metropolitan area (Barcelona, Spain). In order to avoid a potential massive fish kill given the reduced oxygen availability and high fish abundance, preventive purse seine fisheries were performed to reduce the fish stock. The fisheries had little effect on the fish assemblage because final population size structure and species composition did not change significantly. The species composition of the purse seine catches varied significantly during the drawdown with higher proportion of bleak ( Alburnus alburnus) in pelagic water during the days of worst water quality, confirming that bleak is more tolerant than roach ( Rutilus rutilus) to poor water quality and a potential good indicator of water pollution. The weight–length relationship (i.e. condition) of roach and bleak also varied significantly during the drawdown following the same tendency in both species, losing and recovering their weight (4.99% in roach and 5.96% in bleak) in only 16 days. The close relationship found between water quality and fish condition demonstrates that fish condition can be a good metric of the well being of fish, even for extreme short-term changes. [ABSTRACT FROM AUTHOR]

An observer's sampling scheme, that employed fisheries scientists onboard fleet vessels was used to examine temporal fishing tactics and strategies affecting catches of the purse seine fishery in the Mediterranean. The month, water depth and the fishers' behavior were found to have an effect on total and Trachurus spp. retained catches, with fishers' behavior explaining the largest percentage of the data variation. The distance of the fishing ground from port and the market price modulated both the retained catches and the fishing location choice. Results confirmed that fishers while in a specific fishing ground developed strategies that would allow them to retain, and thus land, the best possible combination of landings × market value. The current findings also revealed that, when constrained by physical and economic conditions, fishers preferred to minimise risk rather than maximize landings. The observed major switches in fishing strategy were attributed to fishers' risk attitude response towards higher profitability. As the Mediterranean fishery system is mainly based on control effort and technical measures regimes, the current findings are discussed in the light of the need to consider additional information to management plans and decisions. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a new approach to the analysis of the performance of purse seine fishing gear using a computer simulation. For dynamic simulation, the equation of motion was used to model the shape and movement of the fishing gear as it moved through space during the operations of shooting and pursing. First, a mass-spring model was applied and the equation of motion was described. Second, we developed a simulation tool that can automatically generate a mathematical model from a gear-design drawing. Third, an implicit method for solving nonlinear equations was applied to the calculation. Fourth, the accuracy of the mathematical model used in the simulation was verified by comparing measured and calculated data. Finally, simulations were made using gear rigged in various ways. [Copyright &y& Elsevier]

Purse-seining for tropical tuna is one of the most technologically advanced fisheries in the world. The purpose of this study was to apply local ecological knowledge (LEK) to assist in the planning of future in situ studies of fish behaviour around drifting fish aggregating devices (DFADs) by prioritizing research topics, thereby reducing the number of potential hypotheses to explore. Interviews of fishing masters of the purse-seine fleets working in the western Indian Ocean provided an alternate, independent, and previously unexplored source of behavioural information, specifically on the attraction, retention, and departure behaviours of tuna schools in relation to DFADs. Most fishing masters agreed that the maximum attraction distance of a DFAD is approximately 10 km and generally agreed to the following statements. Tuna form distinct schools under FADs, commonly segregated by species and size. The main reasons for the departure of tuna aggregations from FADs are changes in currents or FAD movements and location in relation to physical or oceanographic features. The number of actively monitored DFADs at sea in the western Indian Ocean was estimated at approximately 2100. Incorporating fishers into the planning and design stages of future research projects will facilitate collaborative and integrated approaches. [ABSTRACT FROM AUTHOR]