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Titill

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

Útdráttur

A decline in the world fish stocks has been documented through scientific studies during the last 30
years. In recent years, fisheries managers have acknowledged that single-species management
approaches ignore the greater ecosystem context. In response, a shift from a single-species
management to ecosystem-based management is occurring. True ecosystem-based management
approaches must consider all aspects of the ecosystem including non-commercial species. This
study uses the data collected from 25 years of scientific trawl surveys to analyze the trends in noncommercial
fin-fish species, which serve as an ecosystem indicator. In this dataset between 508 and
600 stations are surveyed each year (mean 558 stations per year) are sampled. At each station a 4.0
nautical mile trawl is conducted and fish are counted and identified to species level. Species were
selected 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 they
must always be identified to species level. Fifteen species fit the above criteria and were selected for
analysis. Three species (Leptagonus decagonus [Bloch & Schneider], Myoxocephalus scorpius
[Linnaeus], and Cottunculus microps [Collett]) show a decreasing trend in population size while
four 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. Three
species shifted south (Triglops murrayi [Günther], Artediellus atlanticus [Jordan and Evermann],
and C. microps), three species moved north (T. esmarkii, R. cimbrius, Rajella fyllae [Lütken]), three
species migrated west (T. esmarkii, Boreogadus saida [Lepechin], and C. gurardus), and one species
migrated east (C. microps). As would be expected with current warming water temperatures in
Iceland, warm water species tended to increase in population (three out of four) and migrated
north and west. None of the warm water species’ populations decreased. All species with
decreasing populations were cold water species. Interestingly, two cold water species showed a
positive trend in abundance and three cold water species had a southern component to their shift
in distribution. These last results suggest that the role in changing ecosystem regimes and subtle
temperature shifts can influence these species. The population and spatial trends of the species
studied are of particular interest because the changes in these species are not confounded by the
effects of harvest. The results can be used to better understand the effects of climate change on
commercial fish species which occupy similar niches as the fish in the present study.

Birting
22.6.2010


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