Distribution of Neustonic Larvae of Hakes Urophycis spp. and Fourbeard Rockling Enchelyopus cimbrius in the Georges Bank Area

Abstract

The near-surface ichthyoplankton of Georges Bank, Nantucket Shoals, and Gulf of Maine was collected with a modified David neuston katamaran during November 1972-1977. The gear sampled the top 10 cm of the water column with one net and the 20-35-cm-deep stratum with a second. Hake larvae were concentrated in warmer waters of Georges Bank and Nantucket Shoals, including the continental slope; fourbeard rocklings were most abundant in cooler coastal waters of the Gulf of Maine and near Cape Cod. Distribution of the two taxa overlapped only in the temperature range 11-13øC. Hake larvae were more abundant in the upper net during the day than at night, implying diel migrations from the neuston. Fourbeard rocklings were always most abundant in the surface net.

Length–depth relations of Enchelyopus cimbrius fourbeard rockling (Gadiformes: Phycidae) from the southern Gulf of St Lawrence and Cabot Strait in relation to abiotic factors

“…The size of E. cimbrius caught in the southern Gulf of St Lawrence and Cabot Strait (6-39 cm TL) was consistent with previous studies indicating the body size -depth relationship was examined for almost the entire demersal body size-range. Enchelyopus cimbrius has a prolonged pelagic juvenile stage and settles to the bottom at approximately 35 -50 mm (Hermes, 1985) suggesting that fish less than 5 cm are unlikely to be taken on the bottom in deep water. The smallest fish examined in our study were 6 cm long and were presumably recently settled to the bottom.…”

“…Peak spawning takes place in late May and early June in the St Lawrence Estuary (de Lafontaine et al , 1984) and in late June in the southern Gulf of St Lawrence (Hargrave et al , 1985). A prolonged pelagic juvenile stage would allow for several weeks of dispersal in ocean currents before settlement to the bottom at approximately 35–50 mm (Hermes, 1985). Unlike the early settlement stages of many cod-like fish, E. cimbrius does not occur in any abundance in coastal nursery areas off eastern Canada (Macdonald et al , 1984; Black & Miller, 1991; Methven et al , 2001; Wroblewski et al , 2007), hence settlement apparently occurs in deeper water, presumably on a mud substratum that contributes to its sedentary existence and limits the body size–depth sorting over its lifetime.…”

“…Each haul of the bottom-trawl was made at a ship's speed of 3.5 knots for a duration of 30 minutes (mean ¼ 29.26 minutes, +2.44 SD). The mean depth was calculated from the minimum and maximum depths sampled during each haul from 1971-1985. From 1986-2002, the mean depth was calculated as the average of the start and end depths of each haul of the bottom-trawl.…”