Feeding patterns of the plain sculpin Myoxocephalus jaok (Cuvier, 1829) (Cottidae) and its position in the trophic system of near-Kamchatka waters

Feeding patterns of the plain sculpin Myoxocephalus jaok in near-Kamchatka waters of the Sea of Okhotsk, the Bering Sea and Pacific Ocean are considered using materials collected during 1978–2008. This species of Cottidae is characterized by wide feeding spectra (over 100 nutritive objects); nonetheless, fishes (on average 64.1 %) and Decapoda (32.2 %) have the highest significance in its diet. The fishes include flatfish Pleuronectidae (24.3 % of food mass), Alaska pollock Theragra chalcogramma (14.4 %), Pacific sand lance Ammodytes hexapterus (9.5 %), and sculpins Cottidae (5.6 %). Decapoda include crabs from the family Majidae (22.4 %) (Chionoecetes opilio – 14.2 %, Hyas coarctatus – 8.1 %), and Atelecyclidae (4.7 %) (Telmessus cheiragonus – 4.5 %) and shrimps from the family Crangonidae (3.1 %). Seasonal, local, interannual, and age-related changes in food composition of the plain sculpin are considered. This species is a facultative ambuscade predator; it is characterized by a wide feeding spectra that permits it to use a considerable range of food components. In the trophic system of near-Kamchatka regions, units that form the biomass of the plain sculpin are determined.

LONG-TERM AVERAGE BIOMASS AND DOMINANT FISH SPECIES IN THE BOTTOM BIOTOPES OF THE OKHOTSK SEA. PART 1. COMPOSITION AND QUANTITATIVE RATIO OF SPECIES ON SHELVES IN DIFFERENT AREAS OF THE SEA

Composition of the demersal fish community in the bottom biotopes of 14 biostatistical areas of the Okhotsk Sea is considered on the data of 9,189 standard trawl catches obtained in 95 expeditions conducted by Pacific Fish. Res. Center (TINRO) in 1977–2010. The most abundant fish species in each area are ranked by biomass. The total demersal fish biomass is estimated as 9583.0 . 103 t (2124.9 . 103 t without pollock and herring). The most numerous demersal species are: pacific cod Gadus macrocephalus, yellowfin sole Limanda aspera, pacific sand lance Ammodytes hexapterus, great sculpin Mycocephalus polyacanthocephalus, and saffron cod Eleginus gracilis.

Diet of the Pacific Sand Lance (Ammodytes hexapterus) in the Salish Sea, British Columbia, in the 1960s

The diet of the Pacific Sand Lance (Ammodytes hexapterus) was quantified from the stomach contents of 115 Pacific Sand Lance caught in the Strait of Georgia and Saanich Inlet (Vancouver Island) in the Salish Sea, British Columbia, in the spring and summer of 1966, in the Strait of Georgia in the spring and summer of 1967, and in the Strait of Georgia and Saanich Inlet in the spring and summer of 1968. There were 12 major taxa of prey in diets, 8 of which were Crustacea. Based on an index of relative importance, copepods were the dominant prey in 1966 and 1968, but not in 1967, when cladocerans, larvaceans, and teleosts also were common. The copepods Pseudocalanus spp. and Calanus marshallae were the only taxa to appear in diets in all three years. Pseudocalanus dominated the copepod component of diets in 1966, when sampling occurred in July; unspecified copepod nauplii (an early larval stage) were dominant in 1967 and 1968, when sampling occurred earlier (April to June). With the profound changes that have occurred in the Salish Sea over recent decades, these data can serve as a baseline for comparison.

Could the planktonic stages of polar cod and Pacific sand lance compete for food in the warming Beaufort Sea?

The boreal Pacific sand lance (Ammodytes hexapterus) was recently detected in southeastern Beaufort Sea (Canadian Arctic), numbering as the second most abundant ichthyoplankton species after the polar cod (Boreogadus saida) in 2011. We contrast the hatching periods, growth, prey selectivity, and feeding success of the planktonic stages of the two species. Polar cod hatched from January to mid-July and sand lance from mid-July to early September, precluding any competition among the larval stages. By weight, sand lance larvae grew 3.7 times faster than polar cod larvae. The co-occurring juveniles of both species fed primarily on copepods and to a lesser extent on bivalve larvae, shifting to larger prey with growth. The feeding success of both species appeared limited by the availability of their preferred prey. A significant diet overlap in juveniles >25 mm suggested potential competition for Pseudocalanus spp., Calanus spp., and bivalve larvae. However, sand lance strongly selected for nauplii while the more diversified diet of polar cod comprised mainly the copepodites of these species. Interspecific competition for food is unlikely at this time but is predicted to amplify with a climate-related reduction in the size of zooplankton prey and an increase in the abundance of sand lance.