Demersal fish fauna of the continental slope off Nova Scotia, Canada, based on exploratory bottom trawl surveys in 1994�95

Abstract

The demersal fish fauna at 900-1800 m depths off Nova Scotia, Canada, is described using data from exploratory bottom trawl surveys conducted in November 1994 and March 1995 by a commercial fishing trawler. Approximately 25 metric tons (39 000 specimens) of demersal fish belonging to at least 82 species were caught, 30% of which had not previously been recorded from the area. However, more than half the catch consisted of the two species Centroscyllium fabricii (black dogfish) and Coryphaenoides rupestris (roundnose grenadier). Catches were higher in the shallower depth strata fished and cluster analysis showed that depth was the primary factor determining species composition of catches. It is suspected, however, that the vessel fished less effectively at depths greater than about 1500 m, contributing to the reduction in catch quantities at these depths. The importance in catches of large bodied species, particularly Chimaeriformes and sharks, contrasts with results from surveys in adjacent areas. This likely reflects the greater fishing power of the vessel/gear used in present surveys rather than real differences in faunal composition. Catches of mesopelagic species during these surveys, and during an earlier deepwater trawling survey in this area, are also described.

Demersal fishes caught with bottom gillnets and baited gears at 500-2800m on the continental slope off Nova Scotia, Canada

“…All of the species caught during the fixed gear fishing trials described here have been caught previously in otter trawl surveys on the Scotian Shelf slope (Markle et al, 1988;Halliday et al, 2012). However, there were substantial differences between fixed and mobile gears in the relative importance of species in catches, and in species size compositions.…”

“…The relative contributions, by weight, of the top five species caught in gillnets are compared in Fig. 3 to those of the top five species in the otter trawl catches made by Halliday et al (2012). The percentages contributed Fig.…”

“…3. The relative contributions, by weight, of the top five species caught in all gillnets compared to the relative contributions of the top five species to otter trawl catches made on the Scotian Shelf Slope at similar depths (Halliday et al, 2012)…”

“…Minimum sizes of these four species in gillnet catches were substantially higher than in otter trawl catches, as would be expected, but maximum sizes were also higher. However, mean sizes of M. berglax and R. hippoglossoides were similar between gears, likely indicating a scarcity of small fish of these species on the Scotian Shelf slope (Halliday et al, 2012).…”

“…. Mean, minimum and maximum lengths (cm) of the six most abundant species caught in 15 cm gillnets compared to those of catches by small mesh otter trawl (Halliday et al, 2012).…”