DISTRIBUTION OF WITCH FLOUNDER, GLYPTOCEPHALUS 



CYNOGLOSSUS, IN THE SOUTHERN LABRADOR AND EASTERN 



NEWFOUNDLAND AREA AND CHANGES IN CERTAIN BIOLOGICAL 



PARAMETERS AFTER 20 YEARS OF EXPLOITATION 



W R BOWERING 



ABSTRACT 



Witch (lounder were distributed throughout the study area from Hamilton Inlet Bank to the Northern 

 Grand Bank. The main concentrations were located in Hawke Channel, the channel around Funk 

 Island Bank, and the north slopes of the Grand Bank. While these are believed to be the main 

 locations of three separate stocks, there was no apparent discontinuity in the distribution among the 

 three NAFO Divisions investigated. It is clear, however, that the stock located in NAFO Div. 3K is 

 considerably larger than the combined stocks of NAFO Div. 2J and 3L. Stocks showed minimal 

 variations in depth and temperature preference. Depth and temperature preferences were demon- 

 strated for different size and age-classes offish. There were substantial reductions in the number of 

 age gi'oups composing the stocks; this was complemented by increases in mean sizes at age for each 

 stock although the magnitude of this increase varied from one stock to another. There was evidence 

 of reduced size and age at sexual maturity in some instances, however, in most cases the results are 

 difficult to explain. These changes in population dynamics are discussed in relation to changes in 

 exploitation over the past 20 years. 



Prior to the early 1960's, fishing for witch floun- 

 der, Glyptocephalus cynoglossus , in the area of 

 southern Labrador and eastern Newfoundland 

 was practically nonexistent. When a significant 

 fishery began in the early 1960's, catches were 

 taken from the accumulated virgin stock in 

 NAFO (Northwest Atlantic Fisheries Organiza- 

 tion) Div. 2J, 3K, and 3L (Fig. 1) primarily by 

 large offshore otter trawlers from Canada, 

 Poland, and the Soviet Union. Significant catches 

 were also taken by Newfoundland gill net fisher- 

 men in the deepwater bays of northeastern New- 

 foundland (Bowering and Pitt 1974) (Fig. 1). 



Annual landings increased dramatically from 

 < 1,000 t in 1963 to peak at nearly 24,000 t in 

 1973 (Fig. 2). It should be noted, however, that 

 catch statistics prior to 1973 were based upon a 

 formula for breaking down catches of unspecified 

 flounder catches into species and may not be to- 

 tally accurate. Subsequent to 1973, landings de- 

 clined nearly as dramatically as they had risen 

 until they stabilized at about 3.000-5.000 t annu- 

 ally over the period 1980-85. In 1973, ICNAF (In- 

 ternational Commission for the Northwest At- 



iFisheries Research Branch, Department of Fisheries and 

 Oceans, P.O. Box 5667, St. John's, Newfoundland AlC 5X1, 

 Canada. 



Manu.>icnpt accepted April 1987. 



FISHERY BULLETIN: VOL. 8.5. No. 3, 1987. 



lantic Fisheries) decided to place catch quota 

 regulations on witch flounder in this area; for 

 management purposes witch flounder in Div. 2J, 

 3K, and 3L was treated as a single unit (Fig. 1). 

 The first TAC (total allowable catch) was placed 

 on this stock in 1974 at a level of 22,000 t, which 

 was subsequently reduced to 17,000 t for 1975-80, 

 based upon an assessment by Bowering and Pitt 

 (1974). An updated assessment by Bowering and 

 Baird (1980) advised a TAC of 8,000 t for 1981, 

 and this TAC level was in effect up to 1986. The 

 TAC for 1987 was further reduced to 4,000 t. 



Although, for management purposes, witch 

 flounder in Div. 2J, 3K, and 3L is considered a 

 single population (stock), stock delineation stud- 

 ies have shown this not to be the case. Fairbairn 

 (1981), using biochemical systematics (electro- 

 phoresis), distinguished two separate breeding 

 stocks in this area, one in Div. 3K and one in 

 Div. 3L. No data were available from Div. 2J. 

 Bowering and Misra (1982), employing a new 

 multivariate analysis technique on meristic data, 

 corroborated Fairbairn's (1981) findings and also 

 identified a separate stock in Div. 2J. 



The purpose of this paper is to describe the dis- 

 tribution of witch flounder throughout this man- 

 agement zone during recent years and to examine 

 age, growth, and sexual maturity patterns by di- 



611 



