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The tuna fishery resources, particularly yellowfin tuna (YFT), in Ternate waters, North Maluku, Indonesia (fishery management area 715), are currently classified as fully exploited at 0.97% utilization rate of the available potentials, i.e., 31.659 ton/year. This calls for an attempt to manage the yellowfin tuna in such a way that its existence in the waters can be maintained. Studies on fish population parameters are an effort to obtain scientific information as a recommendation for sustainable fisheries management. This research used experimental fishing by measuring the fish's length. Then, its population was estimated using FISAT II program, and its spawning potential ratio (SPR) was analyzed using length based-spawning potential ratio (LB-SPR) software. It was expected that this would be able to give the yellowfin tuna current status and condition in Ternate waters. Conducted from May through August 2023, and analyzing 4,904 fish, the research managed to determine the population parameters of yellowfin tuna in Ternate waters. Its asymptotic length (L8), growth coefficient (K) and t0 were 117.60 cm, 1.4 per year, and 0.17 year, respectively. These were then plotted to obtain a von Bertalanffy growth curve using the formula Lt = 117,60*(1-Exp-1,4(t-0,17). From the analysis, it was found that the fish total mortality, natural mortality and captive mortality rates were 3.89, 1.55, and 2.34, respectively. Furthermore, it was found that recruitment occurred twice a year, i.e., on March and August at 6.72 and 25.18%, with the Y/R value being 0.039 and B/R value of 0.482. Meanwhile, the spawning potential ratio (SPR) value was 19%, indicating that the utilization rate had been over exploited (SPR< 20%) and it was supported by the fact that the exploitation rate value had been over 0.60 (over fishing) from the Emax value (0.421). Therefore, management is needed to ensure the sustainability of yellowfin tuna stocks. [ABSTRACT FROM AUTHOR]

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 (Wt = 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 Lt = 71.17[1 – e-0.215(t +0.130)] and Wt = 102[1 – e-0.215(t +0.130)]2.3839. The estimated longevity tmax 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.

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 study of fishery biology and population dynamics was conducted for Boops boops collected from the commercial catches of gillnets operated in the Egyptian Mediterranean waters off Alexandria. A total of 880 specimens were sampled from the area between Sidi Kirayr to El-Montazah during the period 2018-2020. The length range varied between 11.0 and 20.0 cm TL with a mean of 13.98±1.19 cm and the total weight varied from 14 to 88 g with a mean total weight of 28.51±6.67 g. The length-weight relationship was computed as W= 0.0119 L2.9453 by using total weights and W= 0.0112 L2.9335 by using gutted weights. The mean condition factor (k) was 0.953±0.029 and the overall sex ratio (M: F) was 1.00:0.49. The von Bertalanffy growth parameters were estimated to be K= 0.38 yr-1, L∞= 27.85 cm and tο= -0.443 yr. The growth performance index (Фˋ) was 2.47. The values of natural (M), fishing (F) and total mortality (Z) were calculated as 0.865, 3.845 and 4.710 yr-1, respectively. The current exploitation ratio (Ecur= 0.816) is high reflecting the high exploitation of this species. The yield per recruit and the relative yield per recruit were also studied and the results confirmed that the stock of B. boops is highly exploited and the management of the pelagic gillnets is required. [ABSTRACT FROM AUTHOR]

A total of 500 specimens of Lethrinus variegatus were collected from Attaka fishing port, Gulf of Suez, Egyptian Red Sea waters using the bottom trawlers during 2018 fishing season. The mean total length and mean total weight were 17.05± 2.26cm and 64.46± 5.82g, respectively. The length-weight relationship was computed as [W=.0088L3.1475].The age of specimens varied from I to IV age groups. The Von Bertalanffy growth parameters were estimated as (L∞) = 23.04cm and (K) = 0.6 year-1 while the average total, natural and fishing mortality coefficients were found as 2.08; 0.81; 1.27 year-1, respectively. The relative yield per recruit and average biomass per recruit were determined as a function of LC/L∞ and M/K where it was 0.05 and 0.74, respectively. The exploitation rate (E) was determined using the values of M and F recording 0.61; hence, the stock is considered to be overexploited by the overfishing pressure. [ABSTRACT FROM AUTHOR]

Quantitative fishery harvest strategies in many countries throughout the world are based on maximum sustainable yield (MSY) reference points (RPs); in particular, the fishing mortality rate that produces MSY (i.e. F m s y) and the population biomass (B m s y) that results from fishing at F m s y. There is often great interest in the sensitivity of MSY RPs to their inputs and underlying assumptions. We perturb (i.e. ω) inputs to generate influence curves which we denote as F m s y (ω) and B m s y (ω) as functions of ω. We derive diagnostic equations for the slopes of F m s y (ω) and B m s y (ω) at the origin (i.e. no perturbation). These equations provide a conceptual understanding of how F m s y and B m s y will change in response to changes in inputs, which one does not get from a simple computational sensitivity analysis. We show that a leading factor determining the sensitivity of F m s y is the amount of curvature in the equilibrium yield curve near F m s y. Another leading factor affecting the sensitivity of B m s y is if the stock–recruitment function indicates low density-dependence in recruitment productivity. With some exceptions, we find that F m s y will increase if the body growth rate or asymptotic size increases, 2) proportions mature increase at younger ages, and 3) natural mortality rates decrease and the Ricker stock–recruitment function is used. If the fishery selectivity function of age is monotone increasing then F m s y will also usually increase if peak selectivity is shifted to an older age. Usually the signs of the slopes for B m s y and F m s y are the same. [ABSTRACT FROM AUTHOR]

The deep-sea red shrimp Aristeus antennatus is one of the most valuable demersal resources in Catalonia (northeast Spain), and Palamós is the most important harbour for this fishery in the area. Here, a management plan published in 2013 established the use of a 40-mm square-mesh codend (40s), replacing the previously used 50-mm diamond mesh codend (50d). The objective was to decrease the amount of juveniles in the catches, but the regulation did not bring the expected results. In this study, we measured and compared the selectivity of the 40s and the 50d in this fishery. In addition, we experimented with the use of a 50-mm square-mesh codend (50s). According to our results, the 40s had a lower 50% selection length (L50) than the 50d, while the 50s had a substantially higher L50 than the other two. A transition analysis showed an increase in yield per recruit after the second year from a hypothetical implementation of the 50s. Our conclusion is that the 40s does not have a higher selectivity than the 50d, which (at least partially) explains the failure to reach the management objective in Palamós. Conversely, the use of a 50s would significantly benefit the fishery, increasing gear selectivity and yield per recruit.

Based on growth and related fishery parameters, three approaches, yield-per-recruit (Y/R), utility-per-recruit (U/R) analyses, and relative biomass (B/B0) analyses were applied to 21 economically important, trawl-caught species in China's coastal seas to estimate their relative yield, economic value and biomass under different schedules of fishing mortality and mean length at first capture. The results show that all species suffer from overfishing, given the high average fishing mortality (F ~ 1 year−1) and small mesh size (~1 cm) used by trawlers. Long-term Y/R would double and U/R (expressed as price per landed weight) would increase 5-fold if mesh size were increased to about 10 cm. Comparing Y/R and U/R showed that the benefits of higher prices for larger individuals were detectable only if larger mesh sizes are used, so that individuals are caught only after they have been able to grow. The Y/R analyses also allowed estimating the biomass of the 21 assessed populations relative to their unexploited biomass, i.e., B/B0. Species-specific B/B0 values ranged from 0.01 to 0.58, with a mean of 0.16 (±0.03), i.e., much lower than the 50% reduction corresponding to Maximum Sustainable Yield (i.e., B/BMSY = 1, or B/B0 = 0.5). This confirms the many authors who reported systematic overfishing along China's coastlines, and suggests that rebuilding stocks should be the foremost goal of fisheries management in China.

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]

Hand line gear is the main fishing method used that target sea bass in Bardawill lagoon. The present study was carried out in the lagoon from May to December, 2016 in order to evaluate the by-catch, mortality and yield per recruit. Samples were collected biweekly from three vessels equipped by three lines have live bait. Length at first maturity (Lm50) was estimated. Fish below Lm50 was accounted as a by-catch. Adult and bycatch were recorded as numbers and biomass (kg) per units. By-catch was calculated monthly. Growth parameters, mortality and yield per recruit were determined. The length at first maturity (Lm50) was estimated as 32.5 cm (TL), which corresponding to the second year of life. 40.8% of the Sea bass catch per unit was recorded as a mature fish versus 59.2% as immature ones (by-catch). By-catches are predominant throughout the fishing season except from August to October. Growth parameters; L∞ and K were estimated at 47.25 cm and 0.27 per year respectively. The current exploitation rate (E) was estimated at 0.68 and the total mortality (Z) was 0.83 yr-1. The length at first capture (Lc50) was estimated at 24.5 cm. Relative yield per recruit was 0.68, 0.6 and 0.37 at the maximum (Emax), economic (E0.1) and optimum exploitation (E0.5) respectively. The study recommended that the hook sizes should be increased to capture the mature size ratio Lm/L∞ = 0.65. Fishing from August to October is preferred by hand line gear and prevents at the rest of the fishing season. Exploitation rate should be reduced by 50%. اىص ذٍ تسىاس اىخ ظٍ اى ذٍ يَ اىطش قٌح اىشئ سٍ حٍ اىمسرخذمح ىص ذٍ أسماك اىقاس صَ ف مىخفض اىثشد وٌَ. أخش دٌ اىذساسح ف اىمىخفض مه ما إىى د سٌمثش 6102 ىرق مٍٍ اىمص ذٍ اىعشض اَىىف قُ اَلاوراج اىىسث لأسماك اىقاس صَ مه حشف اىسىاس اى ذٍ يَ. ذم خمع اىع ىٍاخ مو أسث عُ هٍ مه ثلاز ق اُسب، ت 56.3 سم مط هُ)Lm مو قاسب مد ضٍ تثلاثح سىاو شٍ تطعم ح .ً قُذس اىط هُ عىذ ا هَ وضح خىس) 50 ميى. ذم حساب الأسماك ذحد زٌا اىط هُ ممص ذٍ خاوث عذد اًٌ صََو اًٍ)مدم(ىنو حَذج ص ذٍ مَزىل اىمص ذٍ 3 ٪ غ شٍ واضدح)اىمص ذٍ. اىش شٍي. ذم ذسد وٍ 81.4 ٪ مه اىمص ذٍ ىنو حَذج اسماك واضدح مقاتو 6 اىعشض (ً. ذس دُ وسثح اىمص ذٍ اىعشض ط اُه م سُم اىص ذٍ تاسرثىاء اىفرشج مه أغسطس إىى أمر تُش. ذم ذقذ شٌ معا شٌٍ اىىم ،ُ اىط هُ عىذ اىلاو اٍ حٌ ت 82.63 سم سَشع اىىم ت 1.62 سى اًٌُ عيى اىر اُى .ً قُذس سٌا يَ 1.45 ف اىسىح. قُذس اىط هُ عىذ)Z(ت 24% عىذ معذه ميى ىيىف قُ)E(معذه الاسرغلاه اىحاى ،)Emax(1.52 عىذ أقصى اسرغلاه 1.2 ، ت 68.3 سم. اىعائذ اىىسث 1.24)Lc ا هَ ص ذٍ) 50 عيى اىر اُى .ً أ صَد اىذساسح تضش سَج ذعذ وٌ)E اَلاسرغلاه الأمثو) 0.5)E اَلاسرغلاه الاقرصادي) 0.1 حدم اىخطافاخ رَىل ىيص ذٍ عىذ اىحدم اىىاضح. فٌضو ص ذٍ الأسماك ت زٍي اىحشفح ف اىفرشج مه أغسطس إىى أمر تُش مٌَىع تق حٍ م سُم اىص ذٍ. دٌة أن خٌفض معذه الاسرغلاه اىحاى تىسث .٪ [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 LogW = −1.6253 + 2.9832 LogSL 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 to = −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 (ФL) and weight (Фwt) 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 Ecur = 0.58. Length at first capture (Lc) was 9.66 cm at age 0.54 years. Length at recruitment (Lr) was 8.49 cm and age 0.35 years. It was found that the stock of Chrysichthys auratus in Damietta branch was rationally exploited.

Salmonid sport fishery management in Argentinian Patagonia is usually guided by stakeholder perceptions, which do not consider the biological and ecological constraints acting upon aquatic resources. An example of this are management policies for Traful Lake, where Atlantic salmon, Salmo salar L., was actively stocked during the last decade in an attempt to change the fish assemblage structure and to create a highly valuable sport fishery. This study assesses the likelihood of these policies achieving such assemblage structure changes through the study of affluent-stream suitability as spawning and breeding grounds, lake fish assemblage parameters, trophic diversity and possible competition due to diet overlap. This study also assesses alternative management practices through population simulations and bioenergetic modelling under diverse catch-size limit scenarios. This study concludes that it is not advisable to try to generate a unique and distinctive sport fishery by stocking Atlantic salmon in an already renowned fishery in Northern Patagonia. Instead, a more comprehensive framework for decision-making is suggested, involving short-term studies that go beyond the specific problem of the target species and incorporate the whole fish assemblage using diverse approaches and modelling strategies. [ABSTRACT FROM AUTHOR]

Among the several fish species comercially exploited at the Pantanal of Mato Grosso do Sul, the "pacu" (Piaractus mesopotamicus) stands as one of the most important. Information regarding its exploitation level is necessary for the proper management of its stocks. Between 1996 and 1997 data on total length of the pacu were collected on a monthly basis from specimens caught by professional and sport fishers in the municipality of Corumbá. These data were used to estimate growth parameters and to assess the exploitation level for this species, applying the Beverton and Holt yield per recruit model. Length frequency analysis, carried out with the software FISAT (ELEFAN), was used to estimate growth parameters: 1996: L¥ = 87.20 cm; K = 0.34 year-1; phi´=3.41; C = 0.74; WP = 0.81; Longevity = 8.40 years; and 1997: L¥ = 86.50 cm; K = 0.34 year-1; phi´=3.40; C = 0.60; WP = 0.80; Longevity = 8.40 years. The value for t0is -0.363 years for mean values of L¥ and k. The weight-length relationship, calculated from data derived from experimental fisheries carried out in 1999 and 2000, is described by the equation: W = 0.048LF2.835. Estimated mortalities and survival rates were: 1996: Z = 1.51 year-1; M = 0.62 year-1; F = 0.89 year-1; S = 21.9%; and 1997: Z = 1.65 year-1; M = 0.63 year-1; F = 1.02 year-1; S = 19.1%. The yield per recruit analysis showed the following values: F Present= 0.96 year-1; Fmax = 0.67 year-1 ; F0.1 = 0.51 year-1 (for Lc = 26.7 cm). These results suggest that the pacu is overexploited in the area, so that restrictive measures are in need to manage the pacu fisheries.O pacu (Piaractus mesopotamicus) é uma das espécies mais capturadas no Pantanal de Mato Grosso do Sul, e para manejá-lo adequadamente são necessárias informações a respeito do seu nível de explotação. Nos anos de 1996 e 1997 foram coletadas amostras mensais de comprimentos de pacu capturados por pescadores profissionais e esportivos desembarcados em Corumbá, Pantanal de Mato Grosso do Sul (MS), com o objetivo de estimar os parâmetros de crescimento e o seu nível de explotação. Para a determinação do nível de explotação foi utilizado o modelo de rendimento por recruta de Beverton e Holt. Através da análise de freqüência de comprimento, pelo pacote FISAT (ELEFAN), foram estimados os parâmetros de crescimento, com os seguintes valores: 1996: L¥ = 87,20 cm; K = 0,34 ano-1; fi´= 3,41; C = 0,74; WP = 0,81; Longevidade = 8,40 anos; e 1997: L¥ = 86,50 cm; K = 0,34 ano-1; fi´= 3,40; C = 0,60; WP = 0,80; Longevidade = 8,40 anos. O valor de t0 é -0,363 para os valores médios de L¥ e k. A relação peso-comprimento foi determinada através de dados de pescarias experimentais em 1999 e 2000, e foi a seguinte: W = 0,048 LF2.835. As taxas de mortalidade estimadas e a taxa de sobrevivência foram: 1996: Z = 1,51 ano-1; M = 0,62 ano-1; F = 0,89 ano-1; S = 21,9%; e 1997: Z = 1,65 ano-1; M = 0,63 ano-1; F = 1,02 ano-1; S = 19,1%. A análise de rendimento por recruta apresentou os seguintes resultados: Fatual = 0,96 ano-1; Fmáx= 0,67 ano-1 ; F0,1 = 0,51 ano-1 (quando Lc = 26,7 cm). Este resultado indica que o pacu está sobreexplotado, e assim há necessidade de se estabelecer medidas restritivas para sua pescaria.

This paper examines some effects of exploitation on a simple ecosystem containing two interacting fish species, with life histories similar to mackerel ( Scomber scombrus) and cod ( Gadus morhua), using a dynamic, size-spectrum model. Such models internalize body growth and mortality from predation, allowing bookkeeping of biomass at a detailed level of individual predation and growth and enabling scaling up to the mass balance of the ecosystem. Exploitation set independently for each species with knife-edge, size-at-entry fishing can lead to collapse of cod. Exploitation to achieve a fixed ratio of yield to productivity across species can also lead to collapse of cod. However, harvesting balanced to the overall productivity of species in the exploited ecosystem exerts a strong force countering such collapse. If balancing across species is applied to a fishery with knife-edge selection, size distributions are truncated, changing the structure of the system and reducing its resilience to perturbations. If balancing is applied on the basis of productivity at each body size as well as across species, there is less disruption to size-structure, resilience is increased, and substantially greater biomass yields are possible. We note an identity between the body size at which productivity is maximized and the age at which cohort biomass is maximized. In our numerical results based on detailed bookkeeping of biomass, cohort biomass reaches its maximum at body masses <1 g, unlike standard yield-per-recruit models, where body growth and mortality are independent externalities, and cohort biomass is maximized at larger body sizes. [ABSTRACT FROM AUTHOR]

Stocking of young eel is widely practised, as a measure, to meet the management target of the EU eel recovery plan. The target of the recovery plan is to increase the escapement to 40% silver eel biomass, relative to pristine conditions. The scientific information to predict the outcome in silver eel biomass from stocking is limited and may depend on whether translocation of wild glass eel or yellow eel is used, or if the stocked eels used are yellow eel from aquaculture. We evaluated the yield from stocking two different sizes, 3 and 9 g eels from aquaculture. A professional fishery recaptured 12.7% of the 3 g and 9.4% of the 9 g eels, originally stocked. Growth rate and mortality rate were different for the two stocked sizes, favouring the small eels. Brutto yield per recruit (YPR) was 13 and 9.2 g and netto YPR was 9.8 and 0.31 g for 3 and 9 g eel, respectively. We conclude that there seems to be no advantage in using larger 9 g eels compared with small 3 g eels for stocking. [ABSTRACT FROM AUTHOR]

The present study assessed the fishery state of longnose trevally (Carangoides chrysophrys) in the North West Arabian Sea. Key population parameters were estimated, and yield and spawning stock biomass per recruit analyses were conducted. The equation presented by Alagaraja (1984) for estimating natural mortality resulted in M = 0.29 year-1 and lead to the best estimate of longevity. Hence this value was used in the yield and spawning stock biomass per recruit analyses. The total mortality (Z) was estimated as 0.39 year-1, based on a catch curve analysis. Length-at-50% and age-at-50% captures were 38.21cm and 4 years respectively. The yield and spawning biomass per recruit analyses indicate that the current fishing mortality rate (Fcurr) was lower than the fishing mortality corresponding to the maximum yield per recruit (Fmax) and was also higher than the target reference point (F0.1), suggesting that overfishing, currently, does not occur. However, any increase in the fishing effort in the future may lead to overfishing. [ABSTRACT FROM AUTHOR]

The study explores the impacts of varying gillnet mesh size and fishing level on yield per recruit (Y/R), escapement spawning stock (ESS) and mega-spawners (MS) of three widely distributed freshwater fishery target species. Y/R is maximised when the optimal length of capture (Lcap) is above the size of maturity (L50). However, the unimodal shape of gillnet selectivity results in lower impacts to ESS and MS with both smaller and larger mesh sizes. Under conditions of moderate exploitation, the fraction of MS was significantly larger if small meshed gillnets were used. This is due to the relatively smaller cumulative vulnerability from small mesh sizes through time, as they target a smaller size range of fish, which also grow more quickly through the vulnerable window due to higher growth rates. Therefore, unlike trawls and beach seines, which select all size classes beyond the minimum length of capture (Lc), small meshed gillnets are not necessarily destructive and may rather promote sustained production by allowing a higher proportion of the spawning biomass to remain in the stock. The work also helps to explain the observation of sustained fish production in many developing countries despite the persistent use of gillnets of small mesh size that target small, under-sized individuals. [ABSTRACT FROM AUTHOR]

Growth and mortality parameters of greater lizardfish Saurida tumbil (Bloch, 1975) from the Pakistani waters were estimated using length frequency data which were collected from five research trawl surveys during 2009 - 2010. The pooled data of both sexes of S. tumbil consisted of 824 pair of length weight and 2320 length frequency data. The length-weight relationship were at a = 0.011, b = 2.931. The von Bertalanffy growth function parameters were L∝ = 48.30 cm (FL) K = 0.320 year-1 using ELEFAN method and t0 = - 0.786. Based on the growth parameters the total, natural and fishing mortality were estimated at 1.160, 0.716 and 0.444 year-1, respectively. The yield per recruit analysis indicates that, when tc was assumed to be 2, Fmax was estimated as 1.25 and F0.1 at 1.15; when tc was assumed to be 1, Fmax was estimated as 1 and F0.1 at 0.9. Currently we assume that the age at first capture was about 1 year and Fcurrent and was 0.444, therefore Fcurrent was smaller than F0.1 and Fmax. This indicated that the current fishery is in a sustainable condition. When using the Gulland formula biological reference point Fopt was equal to M (0.716). The current fishing mortality rate of 0.444 year-1 was lower than the biological reference point. The exploitation ratio (E) was estimated at 0.382 year-1. In the view of the above results we may assume that the stock of S. tumbil fishery from Pakistani waters is in a sustainable state. [ABSTRACT FROM AUTHOR]

From April 2010 to July 2012 data and samples on the biology and the fishery of Diapterus brevirostris (Teleostei: Gerrei-dae) were collected in the coasts of Colima and Jalisco. Total catches show fluctuations in the last twenty years in Colima. The catches in Jalisco do not show this species alone, but mixed with other "Mojarras" during the last eleven years. The highest catches in Colima and Jalisco are obtained during summer. First age and length of capture was at 2.04 years and 15.00 cm in Colima and 2.98 years and 19.80 cm in Jalisco. Total mortality was Z = 2.06 in Colima and Z = 1.96 in Jalisco. Natural mortality was M = 0.139 in both cases. Fishing mortality was F = 1.921 in Colima and F = 1.821 in Jalisco, with a survival rate of S = 0.127 in Colima and S = 0.141 in Jalisco. Exploitation rate was E = 0.933 in Colima and E = 0.929 in Jalisco. Yield per recruit was y/r = 106.47 g in Colima and y/r = 107.5 g in Jalisco. Increasing the age of first capture to four years old will get a y/r = 146.5 g for Colima and a y/r= 148.2 g for Jalisco. [ABSTRACT FROM AUTHOR]

The stock of Japanese scad Decapterus maruadsi was assessed based on 1864 specimen (combined sexes), collected from the Gulf of Suez during the fishing season 2011/2012. The growth parameters (L∞ & K) have been estimated from length frequency distribution data, and the obtained values were L∞ = 27.31 cm TL and K = 0.53/y. The instantaneous rates of total (Z), natural (M) and fishing (F) mortalities were 1.80, 0.61 and 1.19/y respectively with exploitation ratio (E) of 0.66/y which reflects an over exploitation situation. The estimated length at first capture (Lc) was 12.2 cm, while the length at first sexual maturity (Lm) was 12.3 cm. The relative yield per recruit analysis shows that the stock of D. maruadsi is overexploited and needs to develop a management strategy to conserve and optimize its yield. [ABSTRACT FROM AUTHOR]

The daggertooth pike conger, Muraenesox cinereus ( Forsskål), has become an important fish resource in the western Seto Inland Sea, Japan, since the 1990s. However, introducing sustainable fisheries resource management for this species is difficult in this region because stock assessments have not been performed, and official fisheries statistics for this stock were discontinued after 2007. This study used existing limited data sets to compile the first report for fisheries resource management for this M. cinereus stock. Yield-per-recruit analyses showed that increasing fishing pressure above current levels would provide only a minimal increase in expected catch levels. Hence, the current harvest level is considered to represent the upper limit of fishing pressure. Age composition in a given year could potentially be used to forecast landing abundance for the following 2 years. This study provides a basis for establishing effective fisheries resource management strategies for M. cinereus. [ABSTRACT FROM AUTHOR]

This study was undertaken to suggest an effective fisheries resources management system by using stock assessment and potential yield analyses of crucian carp population in the mid-upper system of the Seomjin River. Fieldwork was conducted seasonally from 2008 to 2009 in the mid-upper system of the Seomjin River. The stock assessment was carried out by the swept area method and the potential yield was estimated by improved fisheries resource potential estimation system based on the Allowable Biological Catch. Also, the yield-per-recruit analysis was used to review the efficient management implication of the resource, Carassius auratus. As a result, the age at first capture (tc) was estimated as 1.468 year, converted body length (BL) was 10.8 cm. Meaning the current fishing intensities, the instantaneous coefficient of fishing mortality (F) was 0.067 year-1, and the yield-per-recruit analysis showed that the current yield per recruit was estimated to be 15.999 g with F and tc. The instantaneous rate of fishing mortality that provides for Allowable Biological Catch (FABC) based on the current tc and F was estimated as 0.618 year-1. Therefore, the optimum fishing intensities could be achieved at the higher fishing intensity for Carassius auratus. The calculated annual stock of C. auratus was estimated as 7,608 kg, and the potential yield was estimated as 343 kg with tc and F at the fixed current level. Using yield-per-recruit analysis, if F and tc were set at 0.618 year-1 and 2 year, the yield per recruit and total allowable catch would be predicted to increase to 62 g and 2,531 kg by about 3.9 times and 7.3 times, respectively. [ABSTRACT FROM AUTHOR]

The middle stretch of the Madeira River has supported an intensive commercial fishery for several decades. Developed in an area of rapids and waterfalls, this fishery focuses primarily on catfish stocks, mainly pimelodids. Data from fish landings collected in the years immediately prior to the start in operations of two large hydroelectric dams were used to estimate growth and mortality rates for Pirinampus pirinampu (Spix & Agassiz) and Brachyplatystoma platynemum Boulenger. In addition, stock assessment was carried out for both species, and the results used to evaluate the status of the fishery. Mean population parameters were L∞ = 80.85 cm (total length), k = 0.52 year-1, ɸ = 3.53, A0.95 = 6 year, M = 0.87, F = 1.41-1.64 and Z = 2.28-2.51 for P. pirinampu; and L∞ = 95.55 cm (total length), k = 0.28 year-1, ɸ = 3.40, winter point = 0.41, A0.95 = 11 year, M = 0.55, F = 0.16-0.35 and Z = 0.71-0.90 for B. platynemum. Yield-per-recruit analysis indicated P. pirinampu was overfished and that the stock of B. platynemum was under-exploited. Moreover, overfishing of the P. pirinampu stock and the effects of fragmentation caused by the construction of the dam should be monitored. [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]

Quantification of demographic parameters is important for understanding how populations interact with their environment and for developing sustainable harvest strategies. Our aims were to quantify demographic parameters and yield of painted spiny lobster (Panulirus versicolor) at Northwest Island, Great Barrier Reef and review fishery management regulations in view of the findings. Using catch-curve analysis and an intensive mark-recapture program, the local lobster population was found to be sparsely distributed (~1.3 ha[sup -1]), with low rates of natural mortality (0.25-0.28 year[sup -1]) and immigration (0.05 ha[sup -1] year[sup -1]). Under current management regulations (no minimum size limit; MSL), yield-per-recruit peaked at 0.38 kg when fishing mortality was 0.4 year[sup -1]. Implementation of a 100-mm (carapace length) MSL is recommended because it provides the best compromise between yield and stock size and has minimal impact on existing fishing practices. Revocation of the prohibition on possessing egg-bearing females is also recommended because it would reduce wastage of lobsters that are inadvertently killed by spear-fishers and because there appears to be little chance of localised recruitment overfishing. This study provides the first estimate of mortality rate for P. versicolor and highlights the importance of this parameter for understanding demographic processes and optimising management regulations. Painted spiny lobster is a popular seafood on coral reefs, but little is known about the biology and fisheries of this species, which increases the risk of over-fishing. We quantified important demographic and fishery-related parameters of painted spiny lobster and subsequently demonstrate that current management regulations are suboptimal. Implementation of sound, knowledge-based management strategies is recommended to help ensure this important fishery resource is harvested on a sustainable and rational basis. [ABSTRACT FROM AUTHOR]

Age and growth of Rachycentron canadum (L.) was studied in northern and eastern Australia to provide data for a preliminary assessment of the stock and to explore possible fisheries management strategies using minimum legal lengths. Fish collected from commercial and recreational fisheries ranged in size and weight from 125 to 1633 mm fork length (FL) and 0.031 to 55 kg respectively. Annual growth increments in sectioned otoliths formed by November–December. Estimated ages ranged from 0 to 7 yr for both genders. Longevity was estimated to be at least 13 yr. Von Bertalanffy growth function parameters were L ∞ = 1160 mm FL, K = 0.63 yr−1 and t0 = −0.21 yr−1. Rachycentron canadum reach 600 mm FL in their first year and over 1000 mm FL in 3 years. Natural and total mortalities were estimated at 0.35 yr−1 and 0.85 yr−1, respectively. Populations of R. canadum may be vulnerable to growth overfishing under the current minimum legal length of 750 mm total length (TL) in Queensland waters. An increase in minimum legal length to 850 mm TL is recommended. [ABSTRACT FROM AUTHOR]

Rapid biological assessments have been proposed as the most cost-effective approach to identify suitable target species and to set initial catch and fishing effort levels for new fisheries. Xonxa Dam, a turbid irrigation dam situated in the White Kei catchment, rural Eastern Cape, is shown to provide fisheries potential for two alien species — smallmouth yellowfish Labeobarbus aeneus and sharptooth catfish Clarias gariepinus — that had been previously introduced into the catchment. Rapid appraisal of the biology, relative abundance, and population dynamics of the fish was effected during three sampling events in 2007. Using a combination of empirical yield and dynamic pool models, it was shown that two discrete fisheries can be developed. For L. aeneus a 60 mm stretched mesh gill net fishery could harvest 23 t y-1 and for C. gariepinus a longline fishery could yield 4 t y-1. The combined fisheries could be valued at c. R135 000 (USD 18 000) per annum. Periodic monitoring would be necessary; firstly, to ensure that spawner biomass per recruit is not reduced below 40% of current levels and, secondly, to refine the potential harvest available from the resource once harvesting is initiated. [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]

Kvamme, C., and Bogstad, B. 2007. The effect of including length structure in yield-per-recruit estimates for northeast Arctic cod. – ICES Journal of Marine Science, 64: 357–368. For northeast Arctic cod (Gadus morhua), traditional age-based estimates of yield per recruit (YPR) are compared with alternative, though comparable, YPR estimates calculated using an age–length-structured model. In the age–length-structured model, growth, fishing mortality, and natural mortality depend only on length, not on age. This model considers possible changes in size-at-age caused by, for example, a length-selective fishery, and therefore, by comparing the different YPR estimates, the importance of considering the stock's length structure can be evaluated. Length- and weight-at-age of stock and catches were influenced by exploitation pattern and pressure. Such changes are not considered in traditional estimates of YPR, for which weight-at-age is fixed and strictly speaking only representative for the current fishery. Consequently, traditional YPR estimates were somewhat higher than the age–length-based estimates for exploiting smaller fish than at present, and the other way round for exploiting larger fish. Both models indicated a gain in YPR for reducing just exploitation pressure (traditional YPR, 13%; alternative model, 20%) or both reducing exploitation pressure and postponing exploitation (traditional YPR, 23–31%; alternative model, 33–48%), compared with the current fishery. [ABSTRACT FROM PUBLISHER]

Through three versions of a handbook on computations for biological statistics of fish populations, W.E. “Bill” Ricker played a pivotal role in founding the field of quantitative fishery science. His interests, however, extended far beyond the confines of quantifiable events to a deep appreciation for the natural world. In this article, I trace his development of fishery models from the 1940s to the 1970s, using examples that illustrate his approach to statistics and biological systems analysis. I describe changes in technology and statistics that have made it possible to extend his research in new directions, although his approach still lies at the core of all modern fishery models. His gentle, inquiring spirit persisted long after his retirement in 1973, as I illustrate from personal experiences with him during the 1990s. [ABSTRACT FROM AUTHOR]

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]

Abstract The Thai river sprat, Clupeichthys aesarnensis Wongratana, is a clupeid with a short life span, and supports artisanal fisheries in a number of reservoirs in the Mekong Basin. The growth parameters, mortality rates and the status of the Thai river sprat in Sirinthorn Reservoir (28 800 ha), NE Thailand (15°N; 105°E), are presented. The fishery is based on lured lift-nets, operated 7–14 days in the new moon period, September to April each year. It was shown that the von Bertalanffy growth function (VBGF) model was L t (mm) = 78.43[1 - exp{-0.211[t - (-0.7996)]}] and its growth conformed to an isometric pattern. Natural mortality rate (month-1 ) was 0.13 month-1 . Total mortality rates ranged from 0.69 to 1.53 month-1 depending on the weather and the fishing season. Recruitment was continuous throughout the year but peaked in June and July. The yield per recruit model indicated that the exploitation rate of this fishery is probably too high. [ABSTRACT FROM AUTHOR]

The article discusses a retrospective and prospective synthesis of results from population models of marine reserves to identify key theoretical issues that appear to be well understood, and issues in need of further exploration. The models focus primarily on questions concerning fishery management at the expense of other objectives such as conservation, scientific understanding, recreation, education, and tourism. Some models remain an aspect of reserve design in need of further analysis.

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]

The von Bertalanffy parameters of growth in Penaeus indicus are estimated as L=218·9 mm, K=2·0 per year, and t =0·01 year in females and 227·2 mm, 1·8 per year and −0·0729 year, respectively in males. The instantaneous rates of mortality are estimated as Z=9·42, M=3·30 and F=6·12 in females and 12·73, 2·90 and 9·83, respectively in males. Various morphometric and length-weight relationships are worked out. At the current rate of fishing, the yield in weight per recruit is 23·05 g in females and 31·74 g in males. There is scope to increase the yield of this species by increasing F (i.e. effort). [ABSTRACT FROM AUTHOR]