We present a method for simultaneously analyzing multiple length frequency data sets. The method utilizes a robust likelihood-based estimation procedure that provides an objective criterion for hypothesis testing. The method is applied to length frequency data from southern bluefin tuna (Thunnus maccoyii) for which independent estimates of growth parameters based on tag return data are available. The estimates of the growth parameters from the new method were found to be in substantial agreement with the values previously obtained for these parameters. The strength of the likelihood approach is demonstrated by discriminating between alternative structural hypotheses for describing the data. The ability to simultaneously analyze multiple samples permits the method to exploit the extra information not available when analyzing samples one by one. The computer program maintains a database of fits to the data which enable the user to organize the results of the analysis. Graphical displays permit the user to view any of the fits, and an interactive graphics routine aids the user to find good initial parameter estimates.

Many of the world’s fish stocks are depleted as a result of overexploitation, pollution and habitat loss. The 2002 World Summit on Sustainable Development (WSSD) sets a target for fisheries to maintain or restore stocks to levels that can produce the maximum sustainable yield (MSY) by 2015. We assessed the global stock status and found that 68% were at or above the MSY level in 2008 and that the 2015 target is unlikely to be met. We compiled data for eight indicators to evaluate the sustainability of fisheries and the gap to meet the WSSD target. These indicators show that the overall condition of global fisheries is declining, long‐term benefits are being compromised, and pressures on fisheries are increasing despite fisheries policy and management actions being taken by coastal States. We develop a bio‐economic model to estimate the costs and benefits of restoring overfished stocks. Our results show that the global fishing capacity needs to be cut by 36–43% from the 2008 level, resulting in the loss of employment of 12–15 million fishers and costing US$96–358 billion for buybacks. On the other hand, meeting the WSSD goal will increase annual fishery production by 16.5 million tonnes, annual rent by US$32 billion and improve biodiversity and functioning of marine ecosystems. However, progress towards rebuilding has been hindered by an unwillingness or inability to accept the short‐term socio‐economic consequences associated with rebuilding fisheries. Thus, there is a pressing need for integration of rebuilding plans into national political and economic decision‐making.

SynopsisStomach content analysis of commercial size cod, Gadus morhua, inhabiting the southwestern Gulf of St. Lawrence are presented for the period May to November 1980. Season-and size-related changes in the diet composition are indicated and the results compared to those of earlier studies. The extent of cod predation on major prey groups is evaluated by estimating their consumption by cod age-groups 3-15. The evaluation is based on the estimate of food intake by individual cod of different ages derived with the aid of a procedure based on Ursin growth theory, estimates of numbers-at-age from cohort analysis and the results of stomach content analysis.With the exception of American plaice, Hippoglossoides platessoides, and snow crab, Chionoecetes opilio, the consumption of commercially important species was relatively low and restricted to older cod. Commercially important species accounted for less than 12% of the total food biomass consumed by cod during the study period. The remainder consisted of other fish (18%), decapods (22%), euphausiids (l5%), molluscs (1 1 %), annelids (8%), and other invertebrates (1.5 %). Methods are suggested to improve the above estimates of total and individual prey biomasses consumed by the fish population.

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