Browsing College of Fisheries and Ocean Sciences (CFOS) by Subject "Otoliths"
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Estimating sizes of fish consumed by ice seals using otolith length-fish length relationshipsArctic fishes and ice seals are key components of the Alaskan Arctic ecosystem. Bearded (Erignathus barbatus), spotted (Phoca largha) and ringed (Pusa hispida) seals are consumers of Arctic marine fishes. Little is known about the sizes of fish that ice seals consume because prey items are digested quickly once exposed to stomach acids. Otoliths, fish ear bones, are often the only parts of a fish that remain in a seal stomach. Otolith length relates directly to fish length, making size estimations of consumed fish possible for piscivore diet studies. Otoliths were measured from fishes collected from cruises in the Beaufort and Chukchi seas during 2009 - 2014. Otolith length - fish length and fish length - fish weight relationships were developed for 11 Arctic marine fish species that are commonly consumed by ice seals in Alaska. Otoliths from seal stomachs provided by subsistence hunters to the Alaska Department of Fish and Game were identified to species level and measured for total length. A mixed effects model was used to determine how the variables of seal species, harvest location, seal age class and sex influenced the sizes of fish consumed. Harvest location and seal age class were the primary factors that affected fish size in ice seal stomachs. Estimating length and weights of fishes consumed by ice seals will help further diet and energetics studies that have not previously been possible in the Alaskan Arctic.
Physical environmental and biological correlates of otolith chemistry of Arctic marine fishes in the Chukchi seaLife history movement patterns in marine fishes can be determined by otolith chemistry if environmental variables are reflected in the otoliths. Arctic cod (Boreogadus Saida), Arctic staghorn sculpin (Gymnocanthus tricuspis), and Bering flounder (Hippoglossoides robustus) are abundant Arctic fishes in the Chukchi Sea with overlapping distributions. Physical environmental data, demersal fishes, bottom seawater, and sediment interface seawater samples were collected from the Chukchi Sea Offshore Monitoring in Drilling Area (COMIDA) cruise on July 30, 2009 and the Russian American Long-term Census of the Arctic (RUSALCA) cruise from September 3 to 30, 2009 in the Chukchi Sea. Magnesium (Mg), strontium (Sr), barium (Ba), and calcium (Ca) were measured with an inductively coupled plasma mass spectrometer (ICP-MS) on the most recent growth edge of otoliths and in whole fish blood, as well as Ba in bottom and sediment interface seawater. Environmental variables and fish age correlated with Arctic cod and Arctic staghorn sculpin otolith signatures while only environmental variables correlated with Bering flounder signatures. Elemental correlations were not always consistent for the variables tested among species. The complexity of this multi-element tool suggests otolith chemistry may not be useful to determine life history movement patterns of these demersal Arctic fishes in offshore waters.