Distribution and biology of blue hake (Antimora rostrata Günther 1878) in the Northwest Atlantic with comparison to adjacent areas

Abstract

Blue hake (Antimora rostrata) are continuously distributed in slope waters off North America and into the Northeast Atlantic. This study focuses on their distribution from the Scotian Shelf in the south to the continental slope just south of Davis Strait. Although most survey effort took place at less than 500 m 91% of survey sets containing blue hake occurred at greater than 500 m. They were found as shallow as 200 m, but percent occurrence at less than 500 m (0.25%) was much lower than at depths exceeding 500 m (reaching 70% at > 1400 m). Catch rate increased steadily to the maximum depths fished with commercial gear and peaked at about 1 400 m in survey trawls, although depths greater than 1 200 m were poorly sampled. Deep (1371-2286 m) longline sets from the 1960s indicated that blue hake were relatively common beyond the standard depths of either scientific surveys or commercial fishing. The deepest capture was from the deepest set fished at 2 286 m. Catch rate increased faster with depth in the southern part of our study area. Sets with blue hake spanned a range of bottom temperatures between 0.9 and 8.7°C, but 97% of the survey sets with blue hake were associated with bottom temperatures greater than 3°C and less than 4.5°C. Fish size (total length or TL) ranged between 5 and 65 cm. Only 29 of 74 569 fish measured from otter trawls were less than 15 cm, but in longline catches, 37 of 867 fish averaging 10 cm TL were taken, amongst the smallest recorded worldwide. Previous studies in US waters found no evidence of spawning and scant evidence of mature individuals and it was thought that spawning might take place to the north in Canadian waters; however, no mature fish, eggs or larvae have been found. The key meristic character used to distinguish North Pacific blue hake from those in other parts of the world was the count of gill filaments. We found considerable overlap in the range of number of gill filaments from our study area compared with those in the North Pacific.