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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 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 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.

Length-based analyses were conducted to assess the stock of the green tiger shrimp Penaeus semisulcatus. Monthly carapace length frequency data were collected from commercial catches at two main landing sites on the Yemeni Red Sea coast for eight months. Growth parameters, mortalities, exploitation rate and yield per recruit were estimated for this species in this area. The estimated growth parameters were CL∞ = 44.65 mm, K = 1.2 yr^-1 and to = -0.15 for males and CL∞ = 58.8 mm, K = 1.4 yr^-1 and to = -0.12 for females. The natural mortality coefficient (M) was estimated as 2.19 yr^-1 and 2.27 yr^-1 for males and females respectively. The total mortality coefficient (Z) was 6.55 yr^-1 for males and 5.63 yr^-1 for females. The exploitation rate was 0.67 and 0.60 for males and females, respectively. Yield per recruit analysis showed that the current exploitation rate will result in higher stock biomass than the maximum exploitation rate.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:42:22Z No. of bitstreams: 1 S1519-69842007000300023.pdf: 234887 bytes, checksum: 7b07c9ed5941092a7fa49319129df8c0 (MD5) Made available in DSpace on 2013-08-22T18:42:22Z (GMT). No. of bitstreams: 1 S1519-69842007000300023.pdf: 234887 bytes, checksum: 7b07c9ed5941092a7fa49319129df8c0 (MD5) Previous issue date: 2007-08-01 Made available in DSpace on 2013-09-30T19:29:32Z (GMT). No. of bitstreams: 2 S1519-69842007000300023.pdf: 234887 bytes, checksum: 7b07c9ed5941092a7fa49319129df8c0 (MD5) S1519-69842007000300023.pdf.txt: 34179 bytes, checksum: 332331ee8b82508632fea5f44cf7d9cb (MD5) Previous issue date: 2007-08-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T15:08:07Z No. of bitstreams: 2 S1519-69842007000300023.pdf: 234887 bytes, checksum: 7b07c9ed5941092a7fa49319129df8c0 (MD5) S1519-69842007000300023.pdf.txt: 34179 bytes, checksum: 332331ee8b82508632fea5f44cf7d9cb (MD5) Made available in DSpace on 2014-05-20T15:08:07Z (GMT). No. of bitstreams: 2 S1519-69842007000300023.pdf: 234887 bytes, checksum: 7b07c9ed5941092a7fa49319129df8c0 (MD5) S1519-69842007000300023.pdf.txt: 34179 bytes, checksum: 332331ee8b82508632fea5f44cf7d9cb (MD5) Previous issue date: 2007-08-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) 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. 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. UNESP Departamento de Ecologia Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA) Pantanal UNESP Departamento de Ecologia

Fork length measurements of individuals of Brycon microlepis landed and commercialized at the Porto Market in Cuiabá, MT, from May-October 1996 to May-October 1997 were used to estimate growth and mortality parameters for this species. The average estimated populational parameters were: L¥ = 705 mm, k = 0.275 year--1, C = 0.775, WP = 0.465, Lc = 164 mm, M = 0.585 year--1, Z = 0.822 year--1, with F = 0.237 year--1. Yield per recruit analysis suggests that the stock is not yet overexploited. Medidas de comprimento furcal obtidas de exemplares de Brycon microlepis desembarcados e comercializados no Mercado do Porto em Cuiabá, MT, no período de maio a outubro de 1996 e de maio a outubro de 1997, foram utilizadas para a obtenção de estimativas dos parâmetros de crescimento e mortalidade da espécie. Os parâmetros populacionais médios estimados foram: L¥ = 705 mm; k = 0,275 ano--1; C = 0,775; WP = 0,465; Lc = 164 mm; M = 0,585 ano--1; Z = 0,822 ano--1, sendo F = 0,237 ano--1. A análise do rendimento por recruta e a taxa de explotação indicam que o rendimento máximo sustentável não foi alcançado. Portanto, o estoque ainda não está sobreexplotado.