Trends in Forage Fish Populations in Northern Hudson Bay since 1981, as Determined from the Diet of Nestling Thick-billed Murres, <i>Uria lomvia</i>

Abstract

ABSTRACT. Trends in the composition of nestling thick-billed murre diets were analyzed for the period 1980 -2002 on the basis of observations of food delivered to nestlings at two breeding colonies in northern Hudson Bay. The incidence of arctic cod, sculpins, and benthic Zoarcidae decreased and the incidence of capelin and sandlance increased over the period considered. Arctic cod fell from a mean of 43% of deliveries in the mid-1980s to 15% in the late 1990s; benthic species (zoarcids and sculpins) fell from 36% to 15%, while capelin increased from 15% to 50% over the same period. July ice cover in Hudson Bay approximately halved during 1981-99. We suggest that the observed changes in diet composition reflect changes in the relative abundance of the fish species involved and that the decline in arctic cod and increase in capelin and sandlance were associated with a general warming of Hudson Bay waters, the result of ongoing climate change in the region.Key words: Hudson Bay, forage fish trends, Uria lomvia, nestling diet, Mallotus villosus, Boreogadus saida, Ammodytes spp., Zoarcidae RÉSUMÉ. On a analysé les tendances dans la composition du régime alimentaire des oisillons du guillemot de Brünnich au cours de la période allant de 1980 à 2002, d'après les observations de l'apport de nourriture aux oisillons à deux colonies de nidification dans le nord de la baie d'Hudson. On a assisté, au cours de cette période, à une baisse de la fréquence de la morue polaire, du chabot et des zoarcidés benthiques, et à une augmentation de celle du capelan et du lançon. La morue polaire a chuté d'une moyenne représentant 43 % de l'apport au milieu des années 1980 à 15 % à la fin des années 1990; les espèces benthiques (zoarcidés et chabots) ont chuté de 36 à 15 %, tandis que le capelan a augmenté de 15 à 50 % au cours de la même période. En juillet, le manteau glaciel dans la baie d'Hudson a diminué de moitié environ entre 1981 et 1999. On suggère que les changements observés dans la composition du régime alimentaire sont un reflet des changements dans l'abondance relative des espèces de poissons concernées et que le déclin de la morue polaire et l'augmentation du capelan et du lançon étaient associés à un réchauffement général des eaux de la baie d'Hudson, réchauffement qui résulte du changement climatique que connaît actuellement la région.

How adaptable are narwhal? A comparison of foraging patterns among the world's three narwhal populations

“…The NHB food web has been changing in the last 30 years as a result of climatic change in the region, which has resulted in an increase in capelin and sandlance (Ammodytes sp.) and a decrease in Arctic cod and some benthic species (Gaston et al 2003). It is possible that, if necessary, narwhals may be able to switch primary prey and monopolize on the increase in capelin abundance, which may mitigate the negative impacts of reduced cod and benthic species.…”

The toxicology of climate change: Environmental contaminants in a warming world

“…Moreover, the rapidity of climate change-induced shifts in habitats and trophic food webs could affect contaminant toxicity by altering exposure pathways and increasing susceptibility of some populations, especially those already under stress (AMAP, 2004;Breivik et al, 2004;Brook and Richardson, 2002;Gaston et al, 2003;Gilbertson et al, 2003;Macdonald et al, 2005;Olafsdottir et al,1998;Sagerup et al, 2000). A limitation of studies investigating the interactive toxicity of climate change and contaminant exposures is that observed biological effects may prove to have a non-linear relationship to the stressors.…”

“…For example, Arctic cod (Boreogadus saida) are a primary, high fat forage fish for many Arctic species, and loss of critical sea ice habitat may adversely affect Arctic cod populations and those animals that rely on them for food. Gaston et al (2003) analyzed the diets of thick-billed murres from 1981-2002, and observed a decrease in consumption of Arctic cod. This shift in diet increased the fat burned to the fat energy gained.…”

Time series data for Canadian arctic vertebrates: IPY contributions to science, management, and policy

“…Marine bird population monitoring in arctic Canada has been key in developing or influencing policies to understand the effects of climate change on these species (Gaston et al 2005a,b), as well as for understanding changes in food webs that might affect reproduction (Gaston et al 2003). For murres, an internationally-harvested species, these monitoring data also contribute to setting harvest limits and understanding the effects of harvest quotas on sustainable management .…”

“…For example, in the case of acid rain in eastern North America, the negative influence of El Niño events on ecosystem recovery was only discerned through interpretation of anomalies in the long-term water chemistry monitoring of lakes and streams (e.g., Dillon et al 1997). Similarly, changes in fish communities in northern Hudson Bay were only recognized by long-term monitoring of seabird diets at Coats Island (Gaston et al 2003). Hence, long-term data are also important in ecology because they generate questioning and reformulating of views of the natural world, challenge current predictions about ecological trends and phenomena, and provide the ability to assess the effectiveness of resource management decisions.…”