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The number of growth rings was counted on broken and burnt otoliths of eight Lethrinus spp. from two local populations: Lethrinus atkinsoni, L. harak, L. miniatus, L. nebulosus, L. obsoletus, L. ornatus, L. ravus, and L. rubrioperculatus, collected from 1985 to 1996 in waters off the Ryukyu Islands. Growth rings were revealed to be formed annually from about October to June by marginal analysis. In addition to obtaining the three parameters in von Bertalanffy growth equation and the maximum age in specimens, the relationship between age and both ovarian maturity rate and sex ratio (percentage female) was analyzed. The age at 50% of ovarian maturity was the lowest at 1-2 years old in L. harak, L. ravus, and L. rubrioperculatus and was the highest at approximately 4 years old in L. nebulosus. The age at which the sex ratio decreased to 50% due to sexual transition from female in protogynous hermaphrodite species was the lowest at 3-4 years old in the L. atkinsoni Okinawa population and was the highest at 7-8 years old in L. miniatus. The oldest maximum age for specimens was 26 years in L. nebulosus and the youngest maximum age was 12 years in L. ornatus.

Sound-speed and density contrasts (h and g, respectively), important acoustic material properties, of Japanese sandeel Ammodytes personatus were measured to estimate theoretical target strength (TS). The measured sound-speed contrast of adult fish varied between 1.016 and 1.023 (mean 1.020), and showed temperature dependence. The measured density contrast differed significantly between juvenile and adult. The density contrast of juvenile varied between 1.017 and 1.024 (1.021), and that of adult varied between 1.026 and 1.038 (1.032). Using these results, TS at 38 and 120 kHz in the fishing season were estimated by an empirical sound scattering model. TS of an individual fish varied significantly with change of tilt angle. TS of near-dorsal aspect (TSsub(max)) and tilt-averaged TS (TSsub(ave)) differed by up to 7 dB. At both frequencies, two different TSsub(ave)-length relationships (TSsub(ave) = a log L + b) were obtained for adult and juvenile. The coefficients of log L of adult were close to 20, suggesting that backscattering strength was proportional to square of body length. These values were larger in juvenile (34.0 at 120 kHz, 56.5 at 38 kHz), suggesting that backscattering strength varied drastically with the cube or fifth power of body length.

The ecosystem approach to fisheries management is high on national, regional and international agendas for sustainable fisheries management. Implementing the Ecosystem Approach to Fisheries covers both theoretical and applied aspects, with a particular emphasis on practical experiences in the form of case studies from around the world, and tools for solutions. Researchers, practitioners and policy makers in fisheries, aquaculture, marine biology and ecology will find this book an invaluable overview and guide to fisheries management.

This work demonstrates the correction of gear-selectivity and retention effects in estimation of growth in fish populations. The selectivity bias can be removed from length-at-age and length increment data. To correct for bias, a maximum-likelihood estimator that incorporates gear selectivity, a size-dependent retention function and several stochastic growth models are provided. The estimator allows the use of joint samples collected by fishing gears with different selectivity, which increases sample size and data representativeness, and thus improves accuracy of population parameter estimates. Data collected from retained tiger flathead caught by Danish seine gear were used for numerical analysis of the selectivity bias. Stock assessment implications of bias in growth estimation are discussed.

Parameters of the length_weight relation (LWR) were estimated for fifteen species of Gerreidae (mojarras) caught from the Pacific- and Atlantic coast of Mexico, including the Gulf of California. The Pacific species were: Diapterus aureolus, Diapterus brevirostris, Eucinostomus currani, Eucinostomus dowii, Eucinostomus entomelas, Eucinostomus gracilis, Eugerres axillaris, Eugerres lineatus, and Gerres cinereus. The Atlantic species were: Diapterus auratus, Eucinostomus argenteus, Eucinostomus gula, Eucinostomus jonesi, Eucinostomus melanopterus, and Eugerres plumieri. The values of the exponent b of the LWR ranged from 2.58 to 3.79. To the best of our knowledge, these are the first parameter estimates for nine species for the Mexican coast and for four on a worldwide scale

:  This study assessed the stock‐recruitment relationship (SRR) for the Japanese sardine Sardinops melanostictus in the North‐western Pacific. Of the 20 SRR models investigated, the Akaike information criterion (AIC) was the minimum (AIC = 551.2) when the data were separated into two groups (A and B) and the log‐normal distribution was applied as the error term. Group A was constructed with SRR data from 1976–1987 and 1992–2004. Group B consisted of data from 1988–1991. The AIC minimum model was R = 22.8 S × eε for Group A, where R, S, and ε denote the recruitment of sardine (individual number of 0‐year old fish), spawning stock biomass (SSB), and error term, respectively. This model indicated that recruitment was proportional to the SSB and that no density‐dependent effect operated over the range of SSB investigated (51 000–11.3 million t). Recruitment was markedly higher (lower) when the sea surface temperature (SST) of the Kuroshio Extension area in February was low (high). The essential SRR can simply be expressed as R = 22.8 S × eε with the level of recruitment deviating from the model to a greater or lesser degree depending on the environmental conditions.

:  The recruitment abundance index of Pacific bluefin tuna Thunnus orientalis was estimated from 1980 to 2003 fishing year by using the troll fishery data in Nagasaki Prefecture, western Japan. It has been shown that the troll fishery in Nagasaki Prefecture operates with good time–area coverage of the species habitat, and that the fishing power slightly changed during the period analyzed, based on fisheries statistics, published information, and interviews with the fishers. Average catch per unit effort (CPUEs) were standardized by a generalized linear model (GLM) considering the effects of fishing year, season and landing area. Standardized CPUE of age‐0 bluefin tuna showed larger fluctuations year by year than the nominal CPUE combined for all ages. High CPUEs in fishing years of 1981, 1994, 1996 and 1999 were observed. Data from these years agreed with the higher recruitments estimated by virtual population analysis (VPA) or higher catch of age‐0 fish reported for the Pacific side. The age‐specific standardized CPUE of age‐0 bluefin tuna in this study was judged to be a useful indicator of recruitment.

Biological parameters, length-frequency distributions and catches of king soldier bream, Argyrops spinifer, in Oman according to fleet (gear/technique) and region was compiled by monthly sampling in 2001 to 2002. Length cohort and yield per recruit analyses were examined. The results showed that: the status of the stock is healthy, the average fishing mortality rate is moderate (0.1) and acts in general on the adult fraction of the stock; An increase in total fishing effort would not lead to any long-term substantial increase of the catch (according the uncertainty of M value); however, the spawning stock biomass would decrease significantly; A moderate (about 20 percentage) modification of minimum length limit in catches would not affect, substantially, the sustainable yield and the spawning stock biomass; Any regulation of trawler fishing by closed season (i.e. restricted trawler activities during some seasons) would not have a significant effect on the long-term yield

:  Population sizes of long‐diving marine mammals can be estimated with minimal bias using line transect sampling techniques in conjunction with data on surfacing/diving, even though the detection probability on the trackline is considerably less than 1. Using a simulation, it was investigated whether population sizes can be accurately estimated when only the mean cue production rate, without information on surfacing/diving patterns, is available. In addition, a new model that incorporates information on surfacing/diving patterns into the estimation procedure was developed. The simulation showed that the new model can provide less biased abundance estimates, whereas neglecting surfacing/diving patterns can result in serious underestimates of abundance, in particular for long‐diving animals.

:  Effects of sampling errors on abundance estimates from virtual population analysis (VPA) were quantified with the bootstrap method for stock of walleye pollock in the the Sea of Japan. In the bootstrap method, individual fish measurements were resampled. A total of 1000 bootstrap samples were produced for each year from 1991 to 2001. The coefficients of variation (CV) of catch at age in 2001 ranged 6.1–33.1%. The CV of an abundance estimate in 2001 ranged 9.0–35.7%. Abundance estimates of the oldest age and the latest year, which had larger CVs than the other estimates, were sensitive to sampling errors. Effects of sampling errors became smaller when the catch at age had been accumulated over a few years. Although VPA includes various types of errors, only the sampling errors have room for improvement in reality. Quantifying the effect of sampling error on VPA estimates is essential for sound and efficient stock management, and is emphasized in this study.