Search

On the upper Niger, two river sections in Mali and Guinea are affected by family and entrepreneurial seine fishing practices leading to seasonal migration phenomena. Although the physical, cultural, social and political contexts are obviously not the same, the existence of entrepreneurial fishermen, owners of large seines – the joba – in Mali and of a smaller size in Guinea – the jolé – is the result of similar processes in terms of their economic organisation and their exploitation of the river environment. The different practices of fishing with the jolé and joba seine nets are important technical indicators of the degree of cohesion and consultation between fishing villages in the same region. In fact, the study of their practices and the places where they are practised informs us of the state of power relations existing on the river and the management of common aquatic territories. [ABSTRACT FROM AUTHOR]

This study identifies differences in vessel efficiency amongst purse seiners in Vietnamese fishery. Deterministic data envelopment analysis (DEA) was used to assess relative capacity utilisation of each vessel, and double bootstrap DEA was adopted to overcome some of the drawbacks of nonparametric DEA. The study was based on a survey of costs and earnings from 52 purse seiners in 2016, revealing an average vessel profit margin of 11%. By adopting double bootstrap DEA while assuming variable returns to scale, mean capacity utilisation was found to be 0.72 (with 95% confidence interval from 0.67 to 0.79). This indicates that to sustain the current catch levels, expected inputs should be reduced by 21-33%. The study shows that vessel size, fishing experience, and family size of skippers, all are factors affecting the capacity utilisation. [ABSTRACT FROM AUTHOR]

Vessel monitoring systems (VMS) represent a tool that can provide information on the spatial and temporal distribution of fishing activity and a quantitative evaluation of the fishing effort at both spatial and temporal scales. The aim of this study was to characterise the spatio‐temporal structure of the Catalan purse seiner fishing effort directed towards anchovy or sardine, which was estimated by filtering VMS data (from 2012 to 2014) by species and seasons. The results showed that the mean location of the fishing effort directed towards anchovy did not vary among the summer seasons, in contrast to the efforts in spring and autumn, whereas the mean location of the effort directed towards sardine was constant over the seasons. The concentration curves indicated that similar fishing effort patterns occurred during all seasons when directed towards sardine, whereas the effort directed towards anchovy was more concentrated in summer. The ranges of the variograms indicated that the fishing effort directed towards both species formed patches. The dimensions of these patches changed from season to season, with the smallest magnitudes during the summer seasons. In this study, a seasonal distribution pattern of the fishing efforts was recognised that adequately captured the features of the distributions of small pelagic populations. [ABSTRACT FROM AUTHOR]

Highlights • Shooting trajectories of purse seines for unassociated (FAD-free) tuna schools were predicted. • Shooting methods were proposed according to the speed of the fish school. • Shooting trajectory was suggested according to the net sinking depth. Abstract Purse seine fishing is very effective in catching large volumes of pelagic fish. In Korea, as in many other countries, it is frequently used in catching tuna, a fish with high added value. To make a successful catch in purse seine fishing, it is important to choose the initial gear shooting position and trajectory for the purse seine based on the speed and direction of the swimming fish and the speed of the ship. In the field, the initial shooting position typically depends on the experience of the captain. With increasingly strict global regulations for fish aggregating devices (FADs), greater precision in predicting the purse seine shooting trajectory is required to improve the catch success rate for unassociated (FAD-free) schools. In this study, we propose trajectories with high potential for application in purse seine fishing, based on the speed and direction of the fish school. Two distinct gear shooting methods are proposed according to the speed of the fish. The first gear shooting method is applicable for fish moving at a moderate speed and with less changes in direction; the second method can be applied to fast-swimming schools. In addition, when the depth covered by the sinker line is known through the analysis of the gear behavior, the gear shooting trajectory can be modified according to the depth of the sinker line. The results from this study may be used as a technological alternative to FAD operations by assisting in tuna resource management and reducing the capture of non-targeted species. [ABSTRACT FROM AUTHOR]

Recommendations and regulations regarding handling of non-target fish (i.e. bycatch) are often vague and subjective in commercial fisheries. Identifying how different components of capture influence the condition of discarded fish can help develop specific guidelines and best handling practices. Using an experimental approach, we modified the severity of capture stressors in commercial purse seine fisheries for Pacific salmon and monitored indices of injury and reflex impairment in chum salmon ( Oncorhynchus keta ), a species commonly discarded from these fisheries. Study fish were held for 5 or 10 days. Modeling of changes in injury and impairment sought to disentangle the latent effects of capture stressors and the role of sex and maturity. Thresholds in physiological responses to times (i) pursed in the net and (ii) air exposed on deck were also evaluated. Injury progressed throughout holding, was more extensive in females, and accelerated faster in less mature fish. Both crowding severity and set size (i.e. estimated number of fish caught) increased injury and impairment, effects that were exacerbated with time pursed. Physiological indicators of exhaustion also increased with time pursed and 15 min was identified as an important transition point, potentially representing the temporal limit to anaerobic exercise. The time between 1 and 3 min of air exposure was identified as being important to survival, and after 6 min of air exposure, endogenous energy stores may have become exhausted. Resulting recommendations include keeping nets loose during sorting, releasing fish prior to 15 min of being pursed, and keeping air exposure within the range of 1–2 min, or less. Additionally, females and less mature fish appear to be more susceptible to the injurious effects of capture. [ABSTRACT FROM AUTHOR]

Concerns about the ecological impact of recent increases in the use of drifting fish-aggregating devices (FADs) have led to implementation of FAD limits worldwide in purse-seine fisheries targeting tropical tunas. However, quantitative analyses supporting such management measures are needed. Analyses of observer data for purse-seine vessels operating in the eastern Pacific Ocean (EPO) during 2012–2015 were conducted. FAD fishing strategies identified in this analysis were found to vary with distance to the coast. Vessels that operated furthest offshore made a large number of FAD deployments and fished primarily on FADs they deployed themselves. Vessels that operated closest to the coast made the fewest FAD deployments and fished about equally on FADs they deployed themselves and on FADs deployed by other vessels. Independent of the FAD fishing strategy, the estimated relationship between deployments and sets was increasing but nonlinear, with a reduced rate of return beyond about 200 deployments. An analysis of the relationship between deployments and standardized catch per successful set, however, provided some support for the hypothesis that more deployments may allow vessels to optimize fishing efficiency. These results highlight the complexity of EPO FAD fishing strategies and have management implications for limits on FAD usage globally. [ABSTRACT FROM AUTHOR]

The shortbill spearfish (Tetrapturus angustirostris) is a rare, large pelagic fish that inhabits the tropical and temperate waters of the Pacific and Indian Oceans, and it is seldom incidentally captured by the purse seine and longline tuna fleets. It is listed on the International Union for the Conservation of Nature red list as data deficient, with the population likely decreasing. The main objective of this paper is to contribute basic knowledge of the species catch rate, spatial distribution, temporal trends, and association with different types of fishing sets. A 23-year (1993-2015) database of incidental catches was analyzed; data was gathered by the observers from the Inter-American Tropical Tuna Commission aboard vessels from the international tuna purse seine fleet in the eastern tropical Pacific Ocean. We also analyzed time series of sea surface temperature (SST) from different Niño regions, and 2 climatic indices, the Oceanic Niño Index (ONI) and the Pacific Decadal Oscillation (PDO). The database included information from a total of 422,970 sets; of these, ~1% resulted in a catch of 687 spearfish. Most incidental catches occurred in waters close to the equator (10°S to 10°N), with no apparent seasonal distribution pattern. Time-series analyses showed a significant positive trend in incidental catch (~4% per year). Weak negative correlations of incidental catches with El Niño SST and ONI suggest that spearfish prefer cool waters in zones near the Equator. The PDO seemed to be more important to spearfish than El Niño events, and it is likely playing an important role in the positive trend of incidental catches. Most spearfish catches were associated with sets made on floating objects, mainly south of the equator and west of 100°W, highlighting the oceanic behavior of this species. [ABSTRACT FROM AUTHOR]

By focusing on a single species and multiple fisheries, this study provides a stock assessment of the Spanish mackerel caught mostly by Korean large trawl (LT), large purse seine (LPS), and large pair trawl (LPT) fisheries. We standardize the fishing efforts for the three fisheries by using a general linear model. We also employ a surplus production model, the Clarke-Yoshimoto-Pooley (CYP) model, based on the Gompertz growth function. The CYP model estimates the maximum sustainable yield, allowable biological catch (ABC), and associated fishing efforts, while a bioeconomic model is used to estimate the maximum economic yield and associated fishing efforts. Furthermore, the study analyzes the economic interactions among the LT, LPS, and LPT fisheries in the Republic of Korea. The economic analysis compares the net profits of the three different axes accruing to the three fisheries from the estimated ABC. The results show that fishing efforts to catch Spanish mackerel have recently risen in the seas of Korea; however, the stock has reduced because of overfishing. Thus, the study's findings suggest that total allowable catch management is necessary for single species and multiple fisheries in order to preserve the Spanish mackerel stock in Korea. [ABSTRACT FROM AUTHOR]

Many capture fisheries worldwide have declined sharply in recent decades or have already collapsed from overfishing, and major fishing grounds are concentrated in zones threatened by pollution, habitat, and coastal zone modification. In Portugal, the European pilchard or sardine (Sardina pilchardus), which is mainly captured by purse seiners (∼98%), is among the species most consumed (along with dried and salted cod), and commercially, it is the most important fish landed in national ports. Besides its consumption as fresh, canned sardine stands out among Portuguese seafood major exports. Although sardine has neither total allowable catch (TAC) nor quota, the Portuguese catch limits for sardine are regulated by the International Council for the Exploration of the Sea (ICES) at the request of the European Union (EU). Therefore, in practice, the ICES advice works as a theoretical TAC. The aim of this article is to diagnose the current state of sardine stocks in the areas where the Portuguese seine fishing is exerted and simultaneously assess if the structural changes induced on the purse seining fleet capacity, in response to the management system currently in force for this fishery, are aligned with its sustainable development. Our major findings conclude that sardine stocks are still exploited at levels that jeopardize the Maximum Sustainable Yield (MSY). Once the unavoidable restructuring of the Portuguese purse seine fleet will inevitably increase unemployment among fishers, we also stress the need to reshape the current Community-Led Local Development (CLLD) program, funded under the EU fisheries structural aid, to make it more effective in minimizing the severe social impacts potentially coming out. [ABSTRACT FROM AUTHOR]

Tuna fisheries catch over three million tonnes of skipjack tuna (Katsuwonus pelamis) each year, the majority of which come from purse-seine vessels targeting fish associated with man-made fish aggregating devices (FADs). A significant challenge for fisheries management is to maximize the efficiency of skipjack tuna catches whilst minimizing the bycatch of small and immature bigeye (Thunnus obesus) and yellowfin (T. albacares) tuna, for which long-term sustainability is uncertain in 75% of the world’s stocks. To better manage the issues common with this fishing method, an improved understanding of tuna behaviour around FADs is necessary. We probabilistically classified the vertical behavioural patterns of 50 bigeye and 35 yellowfin tuna (mean fork length 72cm and 70cm, respectively) electronically tagged throughout the western and central Pacific Ocean into shallow and deep states, using a state-space modelling approach. The occurrence of surface-association behaviours, defined as an individual remaining in a shallow state for 24-hours, was examined in relation to known capture events and FAD density. In general, surface-association events for both species were short and lasted on average less than three days, although events as long as 28 days were observed, and were more common in yellowfin when in archipelagic waters. Events were longest immediately following tagging in 62% and 17% of bigeye and yellowfin, respectively. Surface-association behaviour was not generally estimated just prior to recapture, being either non-existent or shorter than two days for 85% of bigeye and 74% of yellowfin. Current management measures in purse-seine tuna fisheries involve periodic or spatial closures for FAD use. If the chief benefit to purse-seine fishers of surface-association around floating objects is in locating schools in horizontal space at short-term time-scales, rather than holding fish near the surface for extended periods, controlling the number of sets made on FADs should be explored further as an additional management tool. [ABSTRACT FROM AUTHOR]

Multi-beam sonar is commonly used in purse seine fishing to visually evaluate school size and biomass. However, quantitative analyses of the across-beam school dimensions may provide more accurate estimates of school volumes. These may help fishers improve their estimates of fish biomass prior to setting a purse seine set; and assist scientists to more accurately assess the distributions and abundances of pelagic schooling fishes. Fish-school volumes are evaluated using data from a simulated Simrad SX90 sonar. The accuracy of the estimates is dependent on the number of ensonifying beams, and therefore dependent on the school size and range from transducer. We present two models, derived through simulations, to correct for distortions of the target dimensions, both horizontally and vertically. The corrected school heights and widths have precisions of 8.5-10.5% vertically and 6.6-8.7% horizontally. [ABSTRACT FROM AUTHOR]

To ensure efficient and sustainable purse-seine fisheries, the catch process must be monitored to better understand the reactions of fish to the gear. In this study, we monitored the behaviours of herring (Clupea harengus) and mackerel (Scomber scombrus) schools during purseseine capture using a multibeam imaging sonar (Simrad MS70, 75-112 kHz) mounted on a research vessel. The fish behaviours differed between species and purse-seine sets. For both species, the acoustic volume backscattering coefficient increased as 0-80% of the seine was hauled aboard, indicating a corresponding increase in fish spatial density. This increase was significantly greater for herring than mackerel. As 0-40% of the seine was hauled aboard the fishing vessel, schools changed their spatial distribution and volume independent of seine hauling, while for some schools, depth and height decreased. The acoustic volume backscattering strength was up to 25 dB higher in the centre of the school than in the edges. The average lateral target strength was estimated for individual fish in the captured herring schools, and the effect of incident angle on the backscattering strength is considered. [ABSTRACT FROM AUTHOR]

The purse seine fleet in southeastern and southern Brazil has the Brazilian sardine Sardinella brasiliensis as the target species, and fishery management is based solely on its life cycle. This study aimed to analyze a possible overlap of the reproductive cycle and recruitment of the main species caught by seine fleet. During the daily program of industrial fishing monitoring in the ports of Itajaí and Navegantes (Santa Catarina) biometrics were performed twice a month at landings between 2000 and 2013 for posterior analysis in laboratory abroad. The samples analyzed did not include part of the reproductive period and the recruitment due to the closed seasons. The size at first maturity (L50) was obtained by adjusting the proportion of adult females to a logistic model. The reproductive period was determined by analyzing gonadosomatic index and proportion of the maturation stages. Recruitment was determined from the length distribution and the ratio of immature throughout the year. L50 determined was 18.60 cm for S. brasiliensis, 19.58 cm for Opisthonema oglinum, 18.48 cm for Chloroscombrus chrysurus and 21.22 cm for Scomber japonicus. The analyzed species overlapped spawning period between November and April and recruitment in June and July. In the case of directing fishing effort to these non-target species, the possibility of inclusion of these species in closed seasons of target species could ensure a better management and consequently the sustainability of this activity. [ABSTRACT FROM AUTHOR]

Portugal is the third highest per capita consumer of fish in the world, with a fishing fleet consisting of trawlers, purse-seiners and multi-gear vessels, which use a wide variety of fishing gears, such as gillnets, trammel nets, longlines or traps. Climate change affects ocean conditions, impacting marine organisms and ecosystems, with consequences for marine fisheries. The consequences of climate change on fishing communities will depend on their exposure to this factor, the sensitivity of target species and ecosystems to climate change and fishermen’s ability to adapt to climate change. The Portuguese coast is mainly north-south oriented and located in a biogeographic transition zone, between temperate and subtropical waters, where the northern or southern distribution limits of several species can be found. Also, the Portuguese coast is expected to suffer changes in temperature and precipitation more accelerated than the global mean alteration rate, which makes it particularly adequate for studies of the effect of climate change on coastal communities and fisheries. The present study analysed trends in landings of the most important fishing métiers in the Portuguese coast and the vulnerability and adaptation capacity of Portuguese fisheries to climate change. Official Portuguese landings (1992–2012) were analysed and a survey was conducted to assess fishermen’s perception of landings and their potential behaviour in response to the effects of climate change on fisheries. Eighteen new species were landed in Portuguese fisheries over the past 5 years, of which 12 were tropical or subtropical and 5 had their distribution limit along the Portuguese coast. A latitudinal pattern in the number of new species in landings was found, agreeing with a northward shift of subtropical species. The south coast has shown a higher vulnerability to climate change, in terms of both exposure and sensitivity of target species and ecosystems to its effects. Trawlermen may be more adaptable and less vulnerable to climate change, given the high mobility of their fleet. Multi-gear fisheries may be more flexible in changing target species or fishing gear, which makes them potentially less vulnerable to climate change. On the other hand, the high sensitivity of sardine to the effects of climate change makes the purse-seine fisheries particularly vulnerable to climate change. [ABSTRACT FROM AUTHOR]

In this paper, we explore the determinants that affect the exit decisions of vessels in the Spanish small-scale purse seine fishery. Obviously, some of the technical characteristics of the vessels, such as vessel length, engine power, gross registered tonnage and age, can have a significant influence on the decision to leave the fishery. Using survival analysis techniques, we analyse the vessels’ exit decisions from the fishery. Specifically, the Cox proportional hazard model can help identify the factors that influence these decisions. One of these factors is the granting of aid by national and community fishery administrations. Thus, we find that the hazard rate to exit from fishing activity remained more or less constant in the case of vessels that did not receive assistance to exit from fishing activity. Our results also show that fishing vessels operating with a single fishing gear (purse seiner) are more likely to exit than are those that operate using different main fishing gears. Furthermore, we find that vessels with lower incomes are more likely to seek other opportunities in alternative fisheries or industries. The paper concludes that vessels whose overall length is less than 12 m are more likely to exit the fleet than are those with a length between 12 and 15 m. These results indicate the importance of the protection of small-scale fishery and are of concern to its long-term sustainability. [ABSTRACT FROM AUTHOR]

This paper describes the construction of a novel lamp raft for the purse seine fishery and its evaluation in real conditions for 14 days during a six-month period in a freshwater ecosystem (Lake Trichonis, Greece). A simple, but durable and inexpensive design was constructed comprising a LED lamp producing green light, powered by a 12 V battery which is charged by a photovoltaic panel to make the device autonomous concerning its electric power needs. The new lamp raft showed very good technical performance in the field and was found to be more effective at attracting fish than traditional lamp rafts, resulting in higher catch rates for the target fish species ( Atherina boyeri ). The increase in catch varied between 33.3% and 157.1%, with an overall increase of 67.3%. This excellent performance, along with simplicity, durability, and the zero operational cost, makes this raft an interesting candidate to replace the traditional lamp rafts used in purse seine fishery not only in the particular lake for which it was designed, but also in other freshwater and marine ecosystems around the world. [ABSTRACT FROM AUTHOR]

Size-selective fishing operation types and skippers' fishing strategies in operation type combinations were analyzed using fishing data from Thai tuna purse seiners in the Western Indian Ocean during 2005-2007. Catch species and size compositions of tropical tuna, i.e., skipjack, yellowfin and bigeye tunas, were compared among operation types, including free school (FS), fish aggregating device, natural log, and other floating objects operations. FS operation was found to be the most size-selective technique, and caught the fewest small-sized individuals, while the associated operations were less size-selective. Fishing strategy analysis showed that success rates and differences between optimistic and actual values represent economic risk. FS operation holds the highest risk; however, it represents potentially high-revenue fishing because of its ability to catch large-sized individuals and high-priced species. Skipper skills are believed to affect a skipper's fishing strategy, and specialist and generalist skippers were both identified in this analysis. The specialists achieved high revenue by overcoming the risks of FS operation via their skills, while generalists distributed fishing efforts over operation types to avoid risks. Simulation results suggested that high- and moderate- skilled skippers can shift to FS operations with no revenue decline to respond to the policies of the Tuna Regional Fishery Management Organizations, which increasingly promote FS operation. [ABSTRACT FROM AUTHOR]

A series of purse seine survey fishing was conducted in the Eastern Indian Ocean from 1995 to 2003 by M. V. SEAFDEC in order to assess the degree of selective capture in tropical tuna purse seining around drift fish aggregating devices. A new model of size selectivity of a purse seine net was developed as an analytical tool. The model considered retention probabilities on fish encountering a net. The feasibility of selective capture was evaluated by comparing size distributions of skipjack, yellowfin, and bigeye tunas in the catches and selectivity curves for the three species estimated on the model. Size distributions were affected by the selectivity, and sizes at 50 % selectivity were larger than industrially marketable size. Most catch in the three species were commercial sizes, which were selectively retained; however, large proportions of immature yellowfin and bigeye tunas were included in the catch. The exclusion of immature tunas by size selectivity is difficult in multi-species tuna purse seine fishery for commercial purposes. The size selectivity of a net is insufficient as a tool for tuna resource management in multi-species tuna purse seine fishery. The selective capture by other fishing techniques should be pursued for resource management. [ABSTRACT FROM AUTHOR]

Brazilian mullet Mugil liza is a schooling fish that migrates in fall and winter, leaving estuaries and coastal lagoons to spawn in ocean waters. In order to understand the reproductive migration pattern of southern stock along Brazil's coast, we analyzed data collected through the Brazilian Satellite Vessel Tracking Program (Programa Nacional de Rastreamento das Embarcações Pesqueiras por Satélite-PREPS) from 2008 to 2012. The migration period overlaps with the fishing season (May-July) when the licensed purse seine fleet fishes along the southern and southeastern coast of Brazil, motivated to capture mullet by the high value of the roe. During the five fishing seasons the average effort was of 51 active vessels. The average time per season that each vessel navigated in the Speed Compatible with Fishing Operation (SCFO) was 349.3 h, which represented an average of 17% of the total time at sea. From May to July the highest frequency (54%) of SCFO transmissions occurred in June (P < 0.05), and in 95% of the SCFO transmissions the vessels were at depths less than 50 m. The temporal and spatial displacement of the fleet in a south-north direction follows the progression of sea surface temperature SST of 19-21°C (P < 0.05). Most (60%) SCFO signals occurred in areas with this range of temperature, independent of the month and latitude. The south-north displacement of the fleets through the season was similar among the different years (P > 0.05). [ABSTRACT FROM AUTHOR]

The purse-seine tuna fleet in the Western Pacific Ocean has undergone an accelerated expansion since the 1980s. The fishery is primarily managed using fishing effort limits. Constraining effort to ensure the biological health of the stock, while enhancing economic benefits generated by the fishery, is a major challenge faced by fisheries managers in this region. To maintain effort levels that achieve those objectives, there is a need to take into account technical and efficiency changes over time that influence the productivity of fleets. This study evaluates how the productivity of four of the region's purse-seine fleets has changed year on year between 1993 and 2010 using a robust bootstrapped Malmquist index approach. This index is separated into: technical change, which represents the change in productivity due to the introduction of new technology and efficiency change, the change in productivity resulting from a change in the level of efficiency in the use of inputs. The results show that half of the 56 purse-seine vessels examined displayed significant gains in productivity, which appeared to be driven primarily by technical change. The technical efficiency of fleets showed less marked changes, potentially due to the practical inability to maximize performance in the face of dramatic technological advances. [ABSTRACT FROM AUTHOR]

The Ecosystem Approach to Fisheries Management claims that fisheries management should take into account the ecosystem processes; in that context, it is useful to examine the functional traits of fisheries assemblages. This can be a challenge in multispecies fisheries. We used 21 biological traits of 86 species to investigate the relationship between-species and trait composition and to identify species with rare functional traits. Combining these traits with two catch datasets from the eastern Mediterranean (Patraikos Gulf: small-scale fleet, eastern Ionian Sea: entire multispecies fleet), we investigated whether certain fishing tactics or gears tend to remove specific traits, using multivariate methodologies. Species and traits composition of the catches were related, but an important part of trait variability was not explained by species composition. Rare traits and trait combinations were found for important target or bycatch species. Differences in the traits composition of fishing operations were revealed both between fishing tactics (Patraikos) as well as gears and areas (eastern Ionian); hierarchical clustering and MDS indicated the distinction of purse-seine catches at gear level. SIMPER analysis by trait indicated associations of certain trait categories mainly with purse-seines (at gear level) and longline metiers and a trammel-net metier (at metier level). The identification of rare traits or their combinations can have significant management implications as overfishing of the species with these traits could result in altering assemblage functioning. It seems that the multispecies character of the benthic fisheries results in a balanced trait removal, while management should regulate the effects of purse-seine fisheries on the fisheries assemblage functioning. Further investigation of the functions that fishing may remove from the ecosystem could contribute to understanding the effects of fishing and reveal overlooked aspects useful for the improvement of fisheries management. [ABSTRACT FROM AUTHOR]

In the Eastern Tropical Pacific ( ETP), a region of high fishing activity, olive ridley ( Lepidochelis olivacea) and other sea turtles are accidentally caught in fishing nets with tuna and other animals. To date, the interaction between fishing activity, ocean conditions and sea turtle incidental catch in the ETP has been described and quantified, but the factors leading to the interaction of olive ridleys and fishing activity are not well understood. This information is essential for the development of future management strategies that avoid bycatch and incidental captures of sea turtles. We used Generalized additive models ( GAM) to analyze the relationship between olive ridley incidental catch per unit effort ( iCPUE) in the ETP purse-seine fisheries and environmental conditions, geographic extent and fishing set type (associated with dolphins, floating objects or in free-swimming tuna schools). Our results suggest that water temperature, set type and geographic location (latitude, longitude and distance to nesting beaches) are the most important predictor variables to describe the probability of a capture event, with the highest iCPUE observed in sets made over floating objects. With the environmental predictors used, sea surface temperatures ( SST) of 26-30°C and chlorophyll- a (chl- a) concentrations <0.36 mg m−3 were associated with the highest probability of an incidental catch. Temporally, the highest probability of an incidental catch was observed in the second half of the year (June to December). Four regions were observed as high incidental catch hotspots: North and south of the equator between 0-10°N; 0-10°S and from 120 to 140°W; and along the Colombian coast and surrounding regions. [ABSTRACT FROM AUTHOR]

High fishing effort remains in many of the world’s fisheries despite a variety of policies that have been implemented to reduce it. These policies have predominantly focused on models of cause and effect that ignore the possibility that the intended outcomes are altered by social behavior and bounded rationality of autonomous agents. This paper presents a spatially explicit agent-based model for the Philippine tuna purse seine fishery that specifically includes social factors and bounded rationality in the decision making of agents. The model has been informed by interviews, and is verified and validated against data. Sensitivity analysis is used to determine the effects of social factors and bounded rationality on macro-level outcomes (fishing effort, fish stock and industry profit). Three social factors are identified to have considerable effect on these outcomes. These factors are a culturally and personally motivated resistance to exit the business, a social norm regarding the spatial distribution of vessels, and the use of imperfect information by potential entrants in their investment decisions. Existing fishery policies do not explicitly consider these social factors. The results suggest that both research and the management of fishing effort could be improved by viewing fisheries as Complex Adaptive Systems, in which social factors and bounded rationality have a considerable effect on the decision making of fishers (fishermen and fishing companies) and on the macro-level outcomes. [ABSTRACT FROM AUTHOR]

One of the greatest concerns for a successful catch in tuna fishing operations is the diving behavior of the purse seine. To analyze the integrated effect of fishing methods and sea currents on purse seine sinking depth, a multiple regression model was used. This improved model shows current speeds, shooting duration, the included angle between a two-layer current, and net mouth orientation relative to current direction (shooting angle) have an influence on maximum sinking depth. The current in the mid-layer is considered to significantly resist the seine's vertical dive by a quadratic relation, but an increased shooting duration and shooting angle can be enhance the sinking. An obvious difference in terms of sinking depth is found between free-swimming school fishing and floating objects fishing, two common methods in tuna purse seine fisheries. It has been suggested that seine sinking dynamics respond to gear manipulation and, therefore, the model provides useful guidance in implementing net casting for an effective capture. [ABSTRACT FROM AUTHOR]

Modern commercial fisheries are heavily dependent on the input of fossil fuels throughout their supply chains, particularly diesel inputs to fishing vessels. Fuel use intensity of fisheries varies with regard to target species, gears employed, region of fishing, technologies used, skipper behaviour, and other factors. Those fisheries that consume relatively less fuel not only have a lower carbon footprint, up to the point of landing, but are also in a favourable position to meet future fuel and emissions regulations, and may be more resilient to the effects of volatile fuel prices and limited oil resources. We measured fuel inputs to purse seining vessels targeting primarily skipjack ( Katsuwonus pelamis ) and yellowfin ( Thunnus albacores ) tuna. Data reported represent 28% of worldwide landings of skipjack and yellowfin by purse seiners in 2009. These vessels burned, on average, 368 L of fuel per tonne of wet weight landings. This corresponds to a fuel-related carbon footprint of 1.1 kg CO 2 per landed kg of tuna, lower than that of average marine capture fisheries as well as most forms of land-based animal protein production. Interestingly, the use of FADs in purse seine fisheries for tuna was found to be inversely correlated with efficiency, going against conventional logic that FAD use improves efficiency. This study is the largest snapshot of tuna fuel inputs to date, providing a baseline against which future performance can be measured, and an indicator for consumers concerned about the carbon footprint of their food choices. [ABSTRACT FROM AUTHOR]

Vessel position and shooting direction relative to current direction can potentially affect the movement and spatial geometry of purse seine during fishing operations. This study developed an image measurement algorithm to obtain kinetic transformation of a model net when setting in different patterns (shooting with current, front set in shorthand; shooting against current, back set; and shooting lateral to current, cross set) in a specialized purse seine test tank. The results showed some differences in the pattern of deformation in the leadline and floatline. Front set produced the greatest encircled volume by minimizing the area contraction with the open area for floatline in real operation of 0.259 km 2 in cross set, 0.266 km 2 in front set, and 0.257 km 2 in back set, respectively. Different sinking curves were observed in the vertical configuration of middle part of leadline among shooting patterns. Back set is considered as the optimal strategy of setting the net judged from the sinking behavior, as it provides the greatest sinking depth in the middle part of the net. The seiner moved the greatest distance downstream in back set, while the greatest drifting distance inward the circle occurred in front set where it is likely to lead to the seiner drifting over the net. Purse line tension increased continuously until the conclusion of pursing and the bunt was subjected to greater tension force than that at the wing end. [ABSTRACT FROM AUTHOR]

A total of 1230 specimens of bluefish Pomatomus saltatrix (Linnaeus. 1766) were collected by purse seine fishing from January to December 2014 in South Marmara Sea of Turkey. Fish size in total length ranged from 12.3 cm (minimum) in January to 43.7 cm (maximum) in May. Mean of total length 20.57±0.17 cm and mean of weight 94.74±0.41 g was calculated as. The length-weight relationships were determined for males, females, unsexed and combined sexes as W=0.102L2.9763, W=0.0105L2.9638, W=0.0152L2.8348, W=0.0107L2.9574 respectively. All fishes have been found to be isometric (b=3) growth (t test. p>0.05). The results indicated further that the length-length relationships were highly correlated (r²>0.990, p<0.001). [ABSTRACT FROM AUTHOR]

The world tuna fishing fleet is dominated by purse seine boats. Purse seine sets are sometimes unsuccessful in capturing fish; these unsuccessful attempts are known as null sets. Null sets have been widely documented and the numbers indicate that they happen in large proportions. In Mexico, the tuna fishery represents the second most important fishery by volume and value. The frequency of occurrence of null sets during the period 2000-2013 was analyzed to identify the regions, periods, and oceanographic conditions (e.g., ENSO) related to them. Null sets on free-swimming fish schools and between June and July had a higher relative representation. The region with highest relative occurrence was the mouth of the Gulf of California (between August and October). A positive correlation was observed between the occurrence of null sets on free-swimming fish schools and the Multivariate El Niño Index. The maximum values of occurrence of null sets were related to those months in which the water column structure presented changes. Comprehension of this phenomenon (null sets) and its relation to natural events is of importance for the fishery, as there could be repercussions for the economy and management of the resource. [ABSTRACT FROM AUTHOR]

The difficulty of ensuring adequate statistical coverage of whole fleets is a challenge for the implementation of observer programmes and may reduce the usefulness of the data they obtain for management purposes. This makes it necessary to find cost-effective alternatives. Electronic monitoring (EM) systems are being used in some fisheries as an alternative or a complement to human observers. The objective of this study was to test the use and reliability of EM on the tropical tuna purse-seine fishery. To achieve this objective, seven trips of tuna purse seiners operating in the three Oceans were closely monitored to compare the information provided by EM and on-board observers to determine if EM can reliably document fishing effort, set type, tuna catch, and bycatch. Total tuna catch per set was not significantly different between EM and observer datasets; however, regarding species composition, only main species matched between EM and observers. Success on set-type identification using EM varied between 98.3 and 56.3%, depending on the camera placement. Overall, bycatch species were underestimated by EM, but large bodied species, such as billfishes, were well documented. The analyses in this study showed that EM can be used to determine the fishing effort (number of sets) and total tuna catch as reliably as observers can. Set-type identification also had very promising results, but indicated that refinement of the methods is still needed. To be fully comparable with observer data, improvements for accurately estimating the bycatch will need to be developed in the application and use of the EM system. Operational aspects that need to be improved for an EM programme to be implemented include standardizing installation and on-board catch handling methodology as well as improvements in video technology deployment. [ABSTRACT FROM AUTHOR]

Diet studies are an essential component of ecosystem-based approaches to fisheries management. In the eastern Pacific Ocean (EPO), the silky shark ( Carcharhinus falciformis) is the most common species of shark in the bycatch of the tuna purse-seine fishery. A rare, comprehensive dataset of stomach contents of 786 silky sharks sampled in mostly tropical regions of the EPO (25°N-15°S; 79°W-162°W) during 1992-1994 and 2003-2005 was analyzed via classification tree and quantile regression methodologies to gain insight into its ecosystem role. Results suggest that the silky shark is an opportunistic predator that forages on a variety of prey. Broad-scale spatial and shark size covariates explained the feeding habits of silky sharks captured in sets on floating objects, primarily drifting fish-aggregating devices (FADs). A strong spatial shift in diet was identified by the tree analysis, with different foraging patterns in the eastern (inshore) and western (offshore) regions. Greater proportions of FAD-associated prey than non-FAD-associated prey were observed in the diet throughout the EPO, with the greatest proportion in the offshore region. Thus, silky sharks appear to take advantage of the associative behavior of prey fishes to increase their probability of encountering and capturing prey. Evaluation of prey-predator size relationships showed that maximum prey size increased with increasing silky shark size, but minimum prey size remained relatively constant across the range of shark sizes. Results such as these from spatially oriented analyses of predator feeding habits are essential for populating ecosystem models with space-based food webs, which otherwise suffer from generic representations of food webs. [ABSTRACT FROM AUTHOR]

Slipping, the release of fish from the net while it is still in the water is used to adjust catch size or increase catch value in many purse seine fisheries. High fish crowding densities prior to slipping have been shown to result in high mortality of the slipped fish. There are currently no available estimates of fish densities inside the net during purse seining or any practical methods for monitoring the catches or the net during commercial fishing, making the regulation of slipping difficult. In this study, a method for monitoring net volume and shoal size during commercial mackerel ( Scomber scombrus ) purse seining is developed. The net volume for eight separate purse seine sets was monitored during hauling (5 to 80% hauled net) using an omnidirectional fisheries sonar and an acoustic positioning system with transponders mounted in the net wall. The sonar was also used to monitor shoal size and position within the net in one purse seine set. The average volume available to individual fish in the monitored sets was estimated to be above 0.07 m 3 per fish when 80% of the net was hauled. Shoal density was estimated to range between 6 and 31 fish m −3 during the first 60% of hauling. The results indicate that the net volume alone is not directly forcing the mackerel into lethally high densities during the first 80% of hauling, but the estimates are subject to some uncertainty and data is not available for the last and most critical phase of the set. [ABSTRACT FROM AUTHOR]

Bycatch of endangered marine turtles is a growing issue for the management of all fisheries, including the oceanic purse-seine fishery. The aim of this study was to assess the spatial and temporal variation in bycatch rates of these species in the entire European purse-seine fishery operating in the Atlantic and Indian oceans. The study was based on data collected through observer programs from 1995 to 2011. During that period, a total of 15 913 fishing sets were observed, including 6 515 on Drifting Fish Aggregating Devices (DFADs) and 9 398 on free swimming schools, representing a global coverage of 10.3% and 5.1% of the total fishing activity in the Atlantic and Indian Ocean, respectively. Moreover, from 2003 to 2011, 14 124 specific observations were carried out on DFADs to check turtle entanglement in the net covering DFADs. We found that the purse-seine fishery has a very low impact on marine turtles. We estimated that the annual number of individuals incidentally captured was 218 (SD = 150) and 250 (SD = 157) in the Atlantic and Indian Ocean, respectively, with more than 75% being released alive. The present study also investigated the impact of DFADs; which is considered a key conservation issue for this fishery. Drifting objects may play a key role in aggregating juveniles of marine turtles, implying the need for improving their construction to avoid entanglement (e.g. avoiding nets in the structure); however, based on our study it is not the main source of incidental captures of marine turtles in this fishery. [ABSTRACT FROM AUTHOR]

Highlights: [•] In 2013 the EU proposed no discarding ban for the new CFP. [•] Difference between total catches (Illegal, Unreported, Unregulated catches -IUU) and landings is significant. [•] Total catch is 36% higher (range 28.2-41.5%) than officially reported landings. [•] Trawl account for the largest part of unreported catches, followed by multi-gear and purse seine fisheries. [•] IUU amounts have implications for sustainability and balance of trade. [Copyright &y& Elsevier]

Galicia (NW Spain) is an important fishing region with a high potential for cetacean–fishery interactions. Cetacean depredation on catch and damage to fishing gear can potentially lead to substantial economic loss for fishers, while cetacean bycatch raises conservation concerns. With the aim of gathering information on the types and scale of interactions and of suggesting possible management strategies, we conducted face-to-face interviews with fishers in local fishing harbours, in particular to identify specific problematic interactions and to quantify the level of economic loss and bycatch rates associated with these interactions. We found that cetacean–fishery interactions are frequent, although damage to catch and fishing gear by cetaceans was mostly reported as small. Nevertheless, substantial economic loss can result from common bottlenose dolphins (Tursiops truncatus) damaging coastal gillnets and from short-beaked common dolphins (Delphinus delphis) scattering fish in purse-seine fisheries. Cetacean bycatch mortality was reported to be highest for trawls and set gillnets, and probably exceeds sustainable levels for local common and bottlenose dolphin populations. Although interview data may be biased due to the perceptions of interviewees, and therefore should be interpreted with care, the methodology allowed us to cover multiple sites and fisheries within a reasonable time frame. Minimizing cetacean–fishery interactions requires the implementation of case-specific management strategies with the active participation of fishers. For set gillnet and purse-seine fisheries, the use of acoustic deterrent devices (pingers) may prevent cetaceans from approaching and getting trapped in the nets. For trawl fisheries, where bycatch appears to be particularly high at night in water depths of 100–300 m, possible solutions include the implementation of time/area closures and the relocation of some fishing effort to deeper waters. [ABSTRACT FROM PUBLISHER]

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]

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]

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]

Data Envelopment Analysis (DEA) studies of fisheries usually apply output oriented capacity utilization based on physical measures. Although physical measures capture important input factors employed in fishing activities (such as boat size, engine power), economic measures directly reflect the cost of inputs employed. This case study investigates whether economic measures are vital or whether capacity efficiency is sufficiently well reflected solely by the use of physical measures. The analysis makes use of a double bootstrap DEA technique and compares input oriented capacity utilization based on physical versus economic measures. The double bootstrap technique was chosen as it allows statistical inference based on the estimated capacity utilization. The results show that economic measures give a lower capacity utilization than that obtained by physical measures. However, no significant difference was found in the capacity utilizations between the two measures. Truncated regression models indicated that factors such as skipper experience and family size did not significantly affect these two measures of capacity utilization at the 5% level. This study concludes that physical variables are capable of capturing the essential economic differences between vessels. [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]

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]

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.

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]