Spatial and temporal trends of fifteen noncommercial fin-fish species in Iceland between 1985 and 2009

Abstract

A decline in the world fish stocks has been documented through scientific studies during the last 30years. In recent years, fisheries managers have acknowledged that single-species managementapproaches ignore the greater ecosystem context. In response, a shift from a single-speciesmanagement to ecosystem-based management is occurring. True ecosystem-based managementapproaches must consider all aspects of the ecosystem including non-commercial species. Thisstudy uses the data collected from 25 years of scientific trawl surveys to analyze the trends in noncommercialfin-fish species, which serve as an ecosystem indicator. In this dataset between 508 and600 stations are surveyed each year (mean 558 stations per year) are sampled. At each station a 4.0nautical mile trawl is conducted and fish are counted and identified to species level. Species wereselected based on the following criteria: they must not have any commercial value in Iceland(therefore never kept), they must have been captured in more than 1% of the surveys, and theymust always be identified to species level. Fifteen species fit the above criteria and were selected foranalysis. Three species (Leptagonus decagonus [Bloch & Schneider], Myoxocephalus scorpius[Linnaeus], and Cottunculus microps [Collett]) show a decreasing trend in population size whilefour species show increasing populations (Trisopterus esmarkii [Nilsson], Rhinonemus cimbrius[Linnaeus], Gaidropsarus argentatus [Reinhardt], and Chelidinichthys gurnardus [Linnaeus]).Additionally, the geographic center of eight species changed during time period studied. Threespecies shifted south (Triglops murrayi [Günther], Artediellus atlanticus [Jordan and Evermann],and C. microps), three species moved north (T. esmarkii, R. cimbrius, Rajella fyllae [Lütken]), threespecies migrated west (T. esmarkii, Boreogadus saida [Lepechin], and C. gurardus), and one speciesmigrated east (C. microps). As would be expected with current warming water temperatures inIceland, warm water species tended to increase in population (three out of four) and migratednorth and west. None of the warm water species’ populations decreased. All species withdecreasing populations were cold water species. Interestingly, two cold water species showed apositive trend in abundance and three cold water species had a southern component to their shiftin distribution. These last results suggest that the role in changing ecosystem regimes and subtletemperature shifts can influence these species. The population and spatial trends of the speciesstudied are of particular interest because the changes in these species are not confounded by theeffects of harvest. The results can be used to better understand the effects of climate change oncommercial fish species which occupy similar niches as the fish in the present study.