Atlantic Haddock (Melanogrammus aeglefinus)

overview

 

Introduction

Atlantic Haddock (Melanogrammus aeglefinus) is an important commercial species of groundfish found at both sides of the Atlantic. In Nothwest Atlantic it is distributed along Nova Scotian Shelf from Newfoundland down south up to Cape May, NJ (Needler 1930). Zwanenburg (1992) pointed out that there may be anywhere between three and eleven discrete Haddock stocks found in the Northwestern Atlantic. However, despite numerous studies carried out on the species since the 1920s Haddock complex life cycle and the source of significant cyclical recruitment fluctuations are not fully understood. Without comprehensive population genetic studies the level of Haddock population division into individual discrete stocks is discutable at best.
 

Haddock biology

Distribution and movements

Needler (1930) well established Haddock tendency to frequent displacements following optimal temperature (1oC - 10oC) gradients. From his conclusions it is important to note that Haddock are caught in abundance in shallow water above 46 metres in the early spring. As summer proceeds they withdraw to somewhat deeper water, appearing again in shallower water in the late autumn. It is in late autumn when the range of depths in which Haddock appears is greatest. As winter approaches they withdraw again to deeper water, until in midwinter the catch is everywhere made chiefly below 70 metres. Needler observed this to be the general trend of the seasonal changes in Haddock abundance throughout their range, although he notes that it was more pronounced in some localities than in others.

From his own tagging studies and the analysis of tagging done by the US Bureau of Fisheries between 1924-1929, Needler concluded substantial fish movements within individual regions.  Schroeder (1942) lends support to Needler’s observations by his own tagging studies, and so did McCracken (1960) with studies carried out late in 1958-1959 which clearly indicated frequent Haddock displacements between Bay of Fundy, Browns Bank, Georges Bank, South Channel and Nantucket Shoals (NAFO areas 4X, 5Y and 5Z). The Haddock seasonal movements are substantial as evidenced from the seasonal occurrence fluctuations of Haddock in various localities, which Needler clearly documented in his paper. Interestingly, he also notes a consistent fish age gradient existing as one goes from south-west to north-east suggenting substantial migrations of older fish towards north-east (Fig 1).

In conclusion, we know that while Haddock (at least the younger fish) stubbornly return to their favorite spot year after year, it also moves around, migrates and intermixes a lot. The older the fish, the longer are its migrations however and there seem to be evidence for many older fish migrating towards north-east.

Fig. 1 - Haddock age distribution on Scotian Shelf NAFO divisions 5YZ, 4XWVT in 1927. Data adapted from Needler (1930).
 

Reproduction

Spawning occurs between January and June with peak spawning activity taking place in the late March and in April
 

Incomplete
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