Research Document - 2000/144
Status of 4VW American Plaice and Yellowtail Flounder
By G.M. Fowler and W.T. Stobo
The 4VW flatfish management unit comprises three discrete components of American plaice and two discrete components of yellowtail flounder. Separate American plaice populations exist on Banquereau (4Vs) and in Sydney Bight (4Vn), and a transient Gulf of St Lawrence (4T) population may constitute a major but unquantifiable portion of the Sydney Bight fishery in the spring and fall. Both resident populations of plaice appear stable at low abundances, but it is not known if current fishing levels can be sustained. The migratory 4T component in Sydney Bight is at risk, based on 4T research vessel survey estimates, but we cannot track its’ status in 4Vn. Yellowtail flounder populations can be discerned on Banquereau (4Vs) and Sable Island Bank (4W). The Banquereau fish are very tightly distributed near the southeast corner of the bank, and supported a fishery until 1996 when this component was fished out. The 4W yellowtail are widely dispersed and almost entirely of smaller sizes than taken by the fishery, suggesting that the region may serve as a nursery area. There is no indication of a serious fishery for yellowtail in 4W since the early 1970’s.
American plaice exhibit strong trends of declining length at age and declining age at maturity, which has resulted in a large proportion of the stock attaining reproductive status prior to recruitment into the fishery. We believe this to be an evolutionary response to fishing pressure. The same phenomenon would likely be seen with yellowtail flounder if we had age data, based on parallels to plaice in length-weight-maturity trends. This may give these stocks a safety margin against over-exploitation, providing size restrictions are maintained. Less desirably, the trend will greatly diminish the potential yield of these stocks for the future.
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