Understanding the relationship between maturity stages and morphology in relation to size selectivity in trawls is crucial for evaluating the impact of various fishing gear on population structures, fishing mortality rates, and gear efficiency. The krill fishery utilizes different trawl designs and lacks technical regulations specifying permissible gear types and mesh sizes. Therefore, a robust model predicting size selectivity, incorporating morphological variation within the krill population, is needed.
Antarctic krill, both male and female, progress through 12 maturity stages from juveniles to sexually mature adults, each characterized by distinct morphological features. This study provides a detailed morphological description of each krill maturity stage to identify and parameterize factors influencing size selectivity using the FISHSELECT framework. This framework predicts size selectivity for various stages across different mesh sizes and openings relevant to the krill fishery, in both actual and virtual populations. The results can be used to assess size selectivity for specific fishing gears and population structures, enhancing the understanding and modeling of the fishery's impact on the demographic composition of the krill stock.
The predictive population yield model (gRym) offers advice on the catch level for a given area and assesses the status of the krill stock (Constable et al., 1996, 2000; Maschette et al., 2023). The model incorporates krill biomass estimations from acoustic surveys and uses the trawl size selectivity ogive from Krag et al. (2014) to predict the proportion of each length class available to the fishery, thereby estimating the overall proportion of individuals subjected to fishing mortality. The results from this paper can also contribute to gRym by providing a more detailed description of selection for different krill developmental stages.