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Peter J. RUBEC
RUBEC, P.J., J.M. McGLADE, B.L. TROTTIER, A. FERRON, 1991. Evaluation of methods for separation of Gulf of St. Lawrence beaked redfishes Sebastes fasciatus and S. mentella : malate dehydrogenase mobility patterns compared with extrinsic gasbladder muscle passages and anal fin counts. Can. J. Fish. Aquat. Sci., 48: 640-660 .
TROTTIER, B.L., P.J. RUBEC, A.C. RICARD, 1988. Biochemical separation of Atlantic Canadian redfish : Sebastes mentella and S. norvegicus. Can. J. Zool., 67: 1332-1335 .
One of the problems for management of the redfish fishery in the Gulf of St. Lawrence is the difficulty in distinguishing between the different species : deepwater redfish (Sebastes mentella), golden redfish (S. norvegicus), and Acadian redfish (S. fasciatus). Controversy exists concerning whether S. mentella and S. norvegicus are separate species because of similarity of meristic characters and other attributes. We describe a procedure that distinguishes these two forms by isoelectric focusing using polyacrylamide gels of water-soluble muscle proteins. In our samples, the lower part of the gel of S. mentella consistently shows three major protein bands, while that of S. norvegicus shows only one major band. The isoelectric focusing banding patterns from our study agree with those found by other workers for redfish from Greenland and Norway. The unequivocal isoelectric focusing separation and its concordance with morphometric characters indicate that S. mentella and S. norvegicus are genetically distinct, reproductively isolated species. (DBO)©1988 National Research Council Canada
RUBEC, P.J., 1988. Changes in redfish distributions and abundance with reference to changes in bottom temperatures in the Gulf of St. Lawrence from 1983 to 1987. NAFO SCR Doc., 88/92, 24 p .
Marked changes in the distribution and abundance of redfish have occurred in the Gulf of St. Lawrence during the 1980s. A reduction in the catch-per-unit-effort(CPUE)was noted with the standardized commercial CPUE, research vessel CPUE and with logbook data. Weight per two data from summer reseerch vessel surveys was analyzed by means of Duncans Range tests and with a four factor Analysis of Variance. The treatment factors were 5 Temperature Classes, 3 Areas, 4 Years, and Depth Classes. Temperature was found to be a highly significant factor in explaining redfish abundance. Weight per two was significantly higher at 6-8 °C from Duncans Range test. Temperature was the most significant factor in the ANOVA. There was also a weak significance for Depth Class. A second order interaction Depth Class* Years and Duncans tests by Depth Class indicate that redfish changed their depth distributions in response to a contraction and then an expansion of the warm bottom water layer. Area was not significant indicating that redfish exhibited little exchange between areas. A significant third order interaction TClass*DClass*Years appears to have resulted from changes in temperature between years. A cooling trend in 1984 caused the redfish to move into deeper water and may have caused a significant proportion of the biomass to become pelagic. A warming trend which peaked in 1986 allowed redfish to expand their distributions and helped increase their availability to bottom trawling.
Reported landings for the NAFO Divisions 4RST redfish fishery in 1986 were estimated at 33,107 t. Although they constitute a 5,000 t increase from last year, they still represent only 60 % of the TAC. Catch rates for bottom trawls (excluding Engels high-lift), Engels high-lift trawls and midwater trawls were analyzed separately using a multiplicative model. The catch rate series shows 2 distinct peaks, one in 1967-1968 (1.33 t/h) and the other in 1981-1982 (1.29 t/h) and have declined since then; the decline appears to have stopped in 1986. Length frequency distributions based on commercial sampling and research survey data show the presence of 2 strong year-classes : one from the early 1970's (fish about 30 cm) and one from the early 1980's (fish about 20 cm). These smaller fish should be recruiting to the fishery in the next few years. The current biomass (beginning of 1987) was estimated from a non-linear version of the Schaefer general production model to be 473,000 t. Because of uncertainties with regard to the changes in availability of fish to the gear, and therefore the effort levels implied, the recommended catch for 1988 were set at the 2/3fmey equilibrium yield of 56,000 t.
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