The ecology of gadid fishes in the circumpolar Arctic with a special emphasis on the polar cod (Boreogadus saida)

Abstract

In high-Arctic marine ecosystems, the gadids Boreogadus saida (Lepechin, 1774) and Arctogadus glacialis, hereafter referred to as polar cod and Arctic cod, as respective European common names, are foundation species that make up important links between lower and higher trophic levels of the food web (Bradstreet et al. 1986; Christiansen et al. 2012; Hop and Gjosaeter 2013). Other Arctic gadids considered here are the saffron cod [Eleginus gracilis (Tilesius, 1810)], which is endemic to the Pacific Arctic but extends into boreal waters as far south as Japan (Mecklenburg et al. 2002), and its Atlantic sister species, the navaga [Eleginus navaga (Walbaum, 1792)], which is limited to European Arctic and subarctic waters of the Barents, White and Kara seas (Cohen et al. 1990). There is a strong imbalance in the scientific literature regarding these species—a search for the words ‘‘Boreogadus’’ in Google Scholar (April 2016) resulted in 4010 hits, compared to only 522 hits for ‘‘Arctogadus,’’ reflecting a greater emphasis on the more abundant polar cod. The genus ‘‘Eleginus’’ resulted in 1480 hits (E. gracilis: 1070; E. navaga: 408), reflecting the importance of saffron cod as a subsistence resource in parts of the North Pacific. While research on B. saida has a long history, particularly in Russia (Andriyashev 1954; Rass 1968; Ponomarenko 2000; Boitsov et al. 2013), interest in Arctic marine ecosystems has grown in recent years as summer sea ice cover has diminished and water temperatures have increased (Wang and Overland 2009). Arctic gadids, in particular polar cod, have been a focal point for studies of climate impacts (Fortier et al. 2006; Benoit et al. 2008; Bouchard and Fortier 2008; Renaud et al. 2012) and pollution impacts (Christiansen and George 1995; Nahrgang et al. 2010; Dussauze et al. 2014; Geraudie et al. 2014; Andersen et al. 2015). Yet, our current understanding of these important Arctic species is surprisingly fragmented and inconclusive, leaving major gaps in knowledge that prevent a holistic understanding of the interaction between these species and their environment. This special issue contains a collection of manuscripts from an international workshop on the ecology of circumpolar Arctic gadids. The workshop was convened during the Ecosystem Studies of the Subarctic and Arctic Seas (ESSAS) Annual Science Meeting, 8–9 April 2014, in Copenhagen, Denmark. Four of the papers in this collection take a comparative approach across species: Bouchard et al. (2016) compare the early life history of polar cod and Arctic cod, Laurel et al. (2016) contrast the growth rates of four gadids in the North Pacific under different temperatures, Kunz et al. (2016) compare growth of polar cod and Atlantic cod (Gadus morhua) under different temperatures and CO2 levels, and McNicholl et al. (2015) compare diets of two potential competitors, polar cod and capelin (Mallotus villosus). A single paper focuses on saffron cod, specifically their trophic dynamics as inferred from several trophic biomarkers (Copeman et al. 2016). The remaining This article belongs to the special issue on the ‘‘Ecology of Arctic Gadids,’’ coordinated by Franz Mueter, Jasmine Nahrgang, John Nelson and Jorgen Berge.