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The present study was carried out to evaluate the growth pattern and population status of the sea urchin Paracentrotus lividus (Lamarck, 1816) in the Egyptian Mediterranean coast off Alexandria City. A total number of 2575 specimens were collected from their fishing grounds during 2017 to 2018. The size classes ranged from 9–57 mm with a mean value of 34.27 mm. Classes from 27 to 41 mm represented about 81.44% of the total collected catch. The length-weight relationship (W t = 0.0039 L2.3839) reflected a pattern of negative allometric growth. Age was determined using the Bhattacharya's method based on the length frequency data. Six age or cohort groups were recognized. The Von Bertalanffy growth equations for length and weight were found to be L t = 71.17[1 – e-0.215(t +0.130)] and W t = 102[1 – e-0.215(t +0.130)]2.3839. The estimated longevity t max for the Egyptian urchin was 13.96 years. The growth indices for length and weight were Φ' L = 3.04 and Φ' Wt = 0.67. The values of total mortality (Z), natural mortality (M), and fishing mortality (F) were 1.767, 0.47, and 1.297, respectively. The Egyptian urchin population showed an exploitation ratio of 0.73, indicating an over-exploitation status. The results of the yield per recruit and the relative yield per recruit emphasized the urgent need of fishery management strategies to control the fishing practices of the edible purple sea urchin P. lividus for future sustainability of its wild population off the coast of Alexandria. Further work is also needed to investigate other P. lividus populations along the Egyptian Mediterranean coast and assess their health status. [ABSTRACT FROM AUTHOR]

The European pilchard Sardina pilchardus is one of the main target species of the commercial fishery along the Algerian coasts. To better understand the observed decline in catches we studied the state of exploitation and simulated the effect of changing fishing effort on the population of sardines. The Beverton-Holt yield-per-recruit model and the Thompson-Bell model showed that the stock is presently fully exploited. In order to estimate the required model parameters, a sample of 1234 specimens was obtained from commercial catches on the western Algerian coast. Analysis of otoliths and gonads allowed the estimation of age-length model parameters, length-weight relationship, length at first maturity, and length at 50% selectivity. In light of the high vulnerability of small pelagic species to environmental fluctuations one might consider to reduce the current level of exploitation to allow for the annual renewal of the exploitable stock of sardine in the western region of the Algerian coast, and hence for a sustainable yield on the long-term. • European pilchard catches in Algeria decreased twofold in 10 years. • Present fishing mortality F was estimated around 0.5 per year. • Fishery models show that the observed F gives the maximum sustainable yield. • A reduction of F might though be considered in light of environmental fluctuations. [ABSTRACT FROM AUTHOR]

Abstract The striped piggy Pomadasys stridens is a commercial species in the trawl catch of the Suez Gulf. The lengths of collected species ranged from 6.6 to 19.0 cm and showed positive allometric growth W = 0.0074L3.2466. The determination of age derived from the otolith reading revealed that the life span of this species is seven year, which is considered relatively short. The von Bertalanffy equation was calculated as Lt = 20.4 (1−e−0.29(t+1.36)). The estimated size at 50% sexual maturity corresponded to an age close to 1 year, where 9.7 and 11.0 cm were sizes for males and females respectively. The highest Gonado-somatic index (GSI) values were recorded in April and May. The relative yield per recruit (Y'/R) and the estimated biological reference points showed that the species is heavily overexploited which may lead to recruitment overfishing. However, the fishing mortality rate was greater than the target and limit reference points. Also the percentage of the relative biomass per recruit values (which correlated to F0.1 and Fmax) to the virgin biomass was 20.45% and 37.00% respectively, which exceed the percentage of the current biomass per recruit to the virgin biomass (15.49%). The fishery of this species needs some management regulations for the development of its production. [ABSTRACT FROM AUTHOR]

The population structure of three Nemipterid species ( Nemipterus japonicus , Nemipterus bipunctatus and Nemipterus zysron ) from the Gulf of Suez was investigated. A total of 3663 specimens (2597  N. japonicus , 576  N. bipunctatus and 490  N. zysron ) were collected during the fishing season 2014/2015 in the Gulf of Suez. The maximum life span estimated from otolith reading was 5 years for N. japonicus and N. bipunctatus while, it was 4 years for N. zysron . The parameters of von Bertalanffy growth equation were L ∞  = 31.66 cm, K = 0.24 year −1 and t o  = −1.2 year for N. japonicus ; L ∞  = 29.55 cm, K = 0.26 year −1 and t o  = −1.2 year for N. bipunctatus and were L ∞  = 24.69 cm, K = 0.38 year −1 and t o  = −0.84 year for N. zysron . The estimated exploitation rate for the three species exceeded the optimum exploitation rate, indicating an overexploitation of the nemipterid species in the Gulf of Suez. The yield per recruit analysis revealed that the fishing pressure of the trawling fleet in the Gulf of Suez, has overridden the critical level. Findings suggest that decrease in the fishing effort of trawl fishery and increase the length of the mesh size is required for the protection of the nemipteridae resources in the Gulf. [ABSTRACT FROM AUTHOR]

The study of fishery biology of Chrysichthys auratus from Damietta branch, Egypt showed that the population has SL range of 7–20 cm, L ′ = 11.85 cm. Males represent 45.90% and females 53.98% of the population. Length–length and length–weight relationships were analyzed for males, females and combined sexes. It was: SL = −0.6231 + 0.8402 TL and Log W = −1.6253 + 2.9832 Log SL for combined sexes, respectively. The highest values of condition factor were obtained in July, August and September for both sexes. The mean value of ( K ) for males was higher than those of females in all different lengths. Age was assessed by Bhattacharya’s (1967) method from length frequency data to estimate the von Bertalanffy growth parameters ( L ∞ = 26.53 cm, K = 0.214 and t o = −1.569). The individuals of this species live for about 4 years and the first age dominates the population. The growth performance index in length ( Ф L ) and weight ( Ф wt ) was estimated as 2.18 and 1.11, respectively. The mortalities were computed as: Z = 1.44, M = 0.60 and F = 0.84. The exploitation rate was estimated as E cur = 0.58. Length at first capture ( L c ) was 9.66 cm at age 0.54 years. Length at recruitment ( L r ) was 8.49 cm and age 0.35 years. It was found that the stock of Chrysichthys auratus in Damietta branch was rationally exploited. [ABSTRACT FROM AUTHOR]

Abstract: In this study we show how substantial gains towards the goals of ecosystem-based fisheries management (EBFM) can be achieved by different single-species management. We show that fishing has much less impact on stocks if fish are caught after they have reached the size (L opt) where growth rate and cohort biomass are maximum. To demonstrate our point we compare the impact of three fishing scenarios on 9 stocks from the North Sea and the Baltic. Scenario (1) is the current fishing regime, scenario (2) is a new management regime proposed by the European Commission, aiming for maximum sustainable yield obtained from all stocks, and scenario (3) is set so that it achieves the same yield as scenario (2), albeit with fishing on sizes beyond L opt. Results show that scenarios (2) and (3) are significant improvements compared to current fishing practice. However, scenario (3) consistently shows least impact on the stocks, with seven-fold higher biomass of demersal fishes and an age structure similar to an unfished stock. This allows juveniles and adults to better fulfil their ecological roles, a major step towards the goals of ecosystem-based fisheries management. We give examples where scenario (3) is practiced in successful fisheries. We present a new interpretation of the relative yield per recruit isopleth diagram with indication of a new target area for fisheries operating within the context of EBFM. We present a new expression of the relative biomass per recruit isopleth diagram, which supports our analysis. We conclude that size matters for precautionary and ecosystem-based fisheries management and present a list of additional advantages associated with fishing at L opt. [Copyright &y& Elsevier]

Abstract: Sex-specific yield per recruit and spawning stock biomass per-recruit analyses were conducted to evaluate the population status of swordfish in the waters around Taiwan. Estimates of the total mortality rate, obtained from length composition data by catch-curve analysis, are on the order of 0.30year-1 for females and 0.35year-1 for males. Pauly''s empirical method indicates natural mortality rates of 0.25 and 0.27 for females and males, implying that the current fishing mortality rate on either sex is less than 0.1year-1. This is well below the estimates for the target reference points F40% (0.12year-1) and F0.1 (0.20year-1), suggesting the swordfish in the waters around Taiwan are not over-exploited. The spawning potential ratio associated with the current level of exploitation was estimated to be 65% of the pristine level. Isopleths of yield per recruit and spawning stock biomass per recruit generated with various mortality rates suggest that both the yield and spawning biomass per recruit could be increased by raising the age at first capture to a value greater than the age at the onset of sexual maturity. [Copyright &y& Elsevier]

The status of the Maine green sea urchin (Strongylocentrotus droebachiensis) fishery has not been quantitatively determined, despite its commercial importance and declining stock abundances. The high levels of natural variability in the population, and the uncertainty implicit in all fisheries, make it essential to determine probabilistic estimates of current fishing mortality rate and biological reference points for a reliable stock assessment. We used a Monte Carlo simulation approach to investigate how uncertainties associated with yield per recruit parameter estimation would affect F0.1 and Fmax and to identify their impacts on the determination of stock status. We found that higher levels of uncertainty increased variation in F0.1 and Fmax estimates, which translated to a decrease in the probability that the fishery was defined as overfished. F0.1 was considered more appropriate as a target biological reference point, but the probability that the fishery would be defined as overfished varied by confidence level and the magnitude of uncertainty. We suggest that further investigations into other reference points be conducted before final selection and implementation of a management target for the Maine sea urchin fishery. [Copyright &y& Elsevier]

Fishery regulations for Oregon ocean shrimp, Pandalus jordani, are designed to protect age 1 shrimp from overharvest and sustain long-term fishery benefits. Designing appropriate management regulations including minimum mesh size and season dates is complicated by the interaction of natural mortality, fishing mortality, and market factors including prices and revenues. The effects of these variables on management strategies were evaluated using yield per recruit and revenue per recruit models. The model that maximized yield indicated that an early season-opening date was optimal; however, due to size dependent ex-vessel prices, the revenue model suggested that a season-opening delay could generate higher total revenues, while decreasing total effort and total harvest. These results demonstrate that, depending on management objectives, incorporating market information may have a significant effect on selection of regulatory controls in this fishery. [Copyright &y& Elsevier]

Recreational catches of tailor (Pomatomus saltatrix) in Western Australia are regulated by a size and daily catch limit. Short-term mortality rates of angler-caught tailor were investigated to determine the effectiveness of these management strategies in coastal and estuarine waters around Perth, WA. A total of 1155 tailor were caught using five hook types. The overall mortality rate during a 2 h holding period was 3.0%. Legal sized fish had a higher mortality rate than sublegal size fish. Treble hooks produced a significantly higher mortality rate than the other hook types. Although yield per recruit curves calculated using the sublegal fishing mortality estimate for each hook type were similar, yield per recruit calculated using the treble hook mortality was lowest. Ganged hooks with/without terminal trebles were most likely to cause jaw injury while barbed and barbless single hooks were more likely to cause gill injury. Gill injury was responsible for a significantly higher mortality rate than other injury positions. These results suggest current management strategies, including discouraging the use of treble hooks, may be effective in ensuring the survival of a high proportion of sublegal and over the daily catch limit caught and released tailor. [Copyright &y& Elsevier]

Yield per recruit and spawning stock biomass per recruit models were developed to study the interaction between the Taiwanese longline and South African baitboat fisheries for South Atlantic albacore. The Taiwanese longline fleet was found to have a logistically-distributed selectivity pattern with many age classes contributing significantly to the catch. The South African baitboat fleet, on the other hand, had a normally-distributed selectivity pattern with relatively few ages contributing to the catch. This fact profoundly influenced the response of yield and spawning stock biomass per recruit to different levels of fishing mortality exerted by each fleet. The results indicated that, in order to maximize total equilibrium yield per recruit to about 2.2 kg, the South African fishing mortality rate should probably be increased substantially whereas the Taiwanese fishing mortality rate is near optimal. In order to keep the spawning potential ratio above the 20% minimum suggested by Goodyear [Coll. Vol. Sci. Pap. 32 (2) (1989) 487], the Taiwanese apical fishing mortality rate should not exceed 0.55 yr−1, regardless of the South African apical fishing mortality rate. [Copyright &y& Elsevier]