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In Chile, bottom trawling for squat lobsters is one of the most important crustacean fisheries. The fishery has been monitored for the past 15 years to assess the resource status, spatial distribution and effects on benthic species. Understanding the interactions of fishing and non-fishing activities with the benthic communities is of critical importance to estimate the potential bycatch of important economic species from fishing operations and to determine adequate spatial and temporal fishing bans. In this study we characterised the community of the main non-target species caught during historical squat lobster biomass surveys from 2000 to 2015 and interpreted the species included as potential bycatch of the fishery. Four ecological assemblages were found that differed in abundance but not in species richness, which suggests that the community structures did not differ among the areas, but rather in the relative abundances of the species. In addition, we created habitat suitability maps for the groups identified and discuss the effects of the environment and the survey method on the distribution of the groups. Managers can use this information to detect regions with high bycatch risk for demersal trawl fisheries and understand the potential interaction of fishing operations with the environment.

Summary This study examines the seasonal variability in gillnet size selectivity for the main Chilean hake (Merluccius gayi gayi) fishery off the coast of central Chile. Selectivity estimates were based on five gillnet mesh sizes (50, 60, 70, 80, 90 mm) in four traditional fishing areas, and during periods of low and high reproductive activity. Average fish length caught in the earlier period (low reproductive activity) was 30.8 cm LT (±4.17), and significantly longer (p < .05) at 35.9 cm TL (±6.15) in the latter period (high reproductive activity). For males, the selectivity factor was similar in both periods, thus the estimated modal lengths did not differ seasonally (p > .05). For females, however, both the selectivity factor and the estimated modal lengths changed significantly depending on the time of year (p < .05). A significant increment was estimated in the girth/perimeter ratio and condition factor during the period of higher reproductive activity. This change in the fish girth of females during spawning helps explain the significant reduction in their selectivity factor estimates in August–October.

The red squat lobster Pleuroncodes monodon is a species of high commercial value that inhabits the Humboldt Current System. Along the Chilean coast, two populations are exploited by the fishing industry, one located off the coast of Coquimbo and the other off the coast of Concepción. Yet, it is unknown whether there are differences in the “bioenergetic fuel” (measured as lipid content and fatty acid profile) of juvenile populations of these two fishing units and whether these bioenergetic compounds can be modulated by differences in the environmental parameters (such as temperature or chlorophyll-a) of their breeding areas. To shed some light on this, we measured the lipid content and fatty acid profiles of the viscera and muscle of juvenile female red squat lobsters from these two fishing units, specifically from breeding areas near long-exploited fishing grounds: a) the northern fishing unit (NFU, from 26°S to 30°S) and b) the southern fishing unit (SFU, from 32°S to 37°S). We found differences in the lipid content, fatty acid profiles, and ratios of saturated fatty acids (C16:0/C18:0) of juvenile females from these two locations. In addition, the essential fatty acids (DHA/EPA) found in the viscera versus the muscle of these lobsters varied significantly. Juvenile females from the SFU (i.e. Concepción) showed a higher lipid content compared to the juvenile females from the NFU (i.e. Coquimbo). Consistently, individuals from the SFU had a higher content of fatty acids, which also proved to be richer in saturated and monounsaturated fatty acids compared to those from the NFU. Our results are important for the fisheries in both areas because these juvenile populations are the source of new recruits for the adult populations that are exploited by the fishing industry. Our study also aids in determining which populations are healthier or of better quality in bioenergetic terms. Furthermore, increasing the incorporation of bioenergetic parameters in fishery models is essential for the recruitment and stock assessment within an ecosystem approach, since it allows for the evaluation of the nutritional condition of different fishing populations.

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