Assessment of the Northwest Atlantic Mackerel, 

 Scomber scombrus, Stock 



EMORY D. ANDERSON 1 



ABSTRACT 



The status of the Atlantic mackerel, Scomber scombrus, stock in the International Commission 

 for the Northwest Atlantic Fisheries (ICNAF) convention area is analyzed in this paper. Total catch 

 declined from a high of 431,606 tin 1972 to an estimated 92,000 t in 1977. The U.S. spring bottom trawl 

 survey has shown a continuous decrease in Atlantic mackerel abundance since 1968. Fishing mortality 

 (F) in 1977 was estimated at 0.39, nearly one-half of the 1976 level and the lowest since 1972. The 1974 

 year class appears to be the strongest since 1969, whereas the 1975 and 1976 year classes appear to be 

 very weak. Spawning stock biomass decreased from 1 .8 million t in 1970-72 to an estimated 402,500 t at 

 the beginning of 1978, which is slightly below the 1962-67 level when catches averaged only about 

 25,000 t. A zero catch in 1978 would increase the 1979 spawning stock by 6%; a catch of 23,500 t (F = 

 0.07) would maintain the spawning stock at the 1978 level. 



INTRODUCTION 



The following report analyzes the status of the 

 Northwest Atlantic mackerel, Scomber scombrus, stock 

 inhabiting the waters from Cape Hatteras, N.C., to New- 

 foundland, which is the area included in ICNAF (Inter- 

 national Commission for the Northwest Atlantic Fisher- 

 ies) Subareas 3, 4, and 5 and Statistical Area 6 (SA 3-6) 

 (Fig. 1). This assessment provided the basis for 

 establishing the allowable level of catch in 1978 in the 

 southern part of this area (SA 5-6) and was used by the 

 National Marine Fisheries Service for its environmental 

 impact statement/preliminary fishery management plan 

 for the Atlantic mackerel fishery and by the Mid- 

 Atlantic Fishery Management Council for its environ- 

 mental impact statement/fishery management plan for 

 this fishery. 



In previous years, this stock was managed through IC- 

 NAF, and assessments were completed jointly by scien- 

 tists from various member nations within the ICNAF 

 Assessments Subcommittee. The last such assessment, 

 on which the 1977 total allowable catch (TAC) was 

 based, was made at the time of the Ninth Special 

 Meeting of ICNAF held at Puerto de la Cruz, Tenerife, 

 Canary Islands, Spain, in November-December 1976 (IC- 

 NAF 1977). Separate assessments submitted by 

 Anderson et al., 2 Isakov et al., 3 and Ivanov 4 provided the 



■Northeast Fisheries Center Woods Hole Laboratory, National Marine 

 Fisheries Service, NOAA, Woods Hole, MA 02543. 



2 Anderson, E. D„ P. W. Wood, B. B. Ackerman, and F. P. Alme- 

 ida. 1976. Assessment of the mackerel stock in ICNAF Subareas 3- 

 6. Int. Comm. Northwest Atl. Fish. Res. Doc. 76/XH/137, Ser. No. 4033 

 (mimeogr.), 21 p. 



'Isakov, V. I., L. Ivanov, P. Kolarov, W. Mahnke, A. Paciorkowski, 

 V. A. Rikhter, S. Ucinski, and B. Vaske. 1976. Reassessment of the 

 mackerel stock in the ICNAF area. Int. Comm. Northwest Atl. Fish. 

 Res. Doc. 76/XII/169, Ser. No. 4065 (mimeogr.), 10 p. 



'Ivanov, L.S. 1976. Relative assessment of mackerel stock in the IC- 

 NAF area and forecast of the possible catch in 1977. Int. Comm. North- 

 west Atl. Fish. Res. Doc. 76/XII/135, Ser. No. 4030 (mimeogr.), 7 p. 



basis for the 1976 assessment. In addition to this paper, 

 catch projections for 1978 were provided by Isakov 5 and 

 several unpublished Canadian reports (Hunt 6 ; Lett and 

 Hunt 7 ; and Lett and Marshall 8 ). 



Data utilized here include international commercial 

 and U.S. recreational catch statistics for 1961-77 and 

 U.S. research vessel bottom trawl survey results for 1963- 

 77. Results include estimates of fishing mortality, stock 

 size, recruitment, and projected catch options for 1978, 

 with the resulting spawning stock biomass levels for 

 1979. 



METHODS 



International commercial Atlantic mackerel catches 

 for 1961-76 were obtained from ICNAF Statistical Bul- 

 letins published in 1963-77 (volumes 11-26), provisional 

 catches for January-March 1977 were obtained from IC- 

 NAF Circular Letters, and catches for the remainder of 

 1977 were estimated. 



Various marine angler surveys provided estimates of 

 the 1960, 1965, 1970, 1974, and 1976 U.S. recreational 

 catches of Atlantic mackerel (Clark 1962; Deuel and 

 Clark 1968; Deuel 1973; Deuel 9 ; Christensen et al. 10 ). 



6 Isakov, V. I. 1977. Estimation of stock and total allowable catch of 

 mackerel in the Northwest Atlantic for 1977-78. Int. Comm. Northwest 

 Atl. Fish. Res. Doc. 77/VT/41, Ser. No. 5066 (mimeogr.), 6 p. 



6 Hunt, J.J. 1977. Data tables mackerel — Subareas 3-6. Can. Atl. 

 Fish. Sci. Adv. Comm., Working Pap. 77/6, 3 p. CAFSAC, P.O. Box 1006, 

 Dartmouth, Nova Scotia B2Y 4A2. 



'Lett, P. F., and J. J. Hunt. 1977. A preliminary study of some bio- 

 logical factors related to the assessment of mackerel. Can. Atl. Fish. 

 Sci. Adv. Comm., Working Pap. 77/19, 16 p. 



•Lett, P. F., and W. H. Marshall. An interpretation of biological fac- 

 tors important in the management of the northwestern Atlantic mack- 

 erel stock. Department of Fisheries and Environment, Fisheries and 

 Marine Service, Bedford Institute of Oceanography, Dartmouth, Nova 

 Scotia, B2Y 4A2. Unpubl. manuscr., 37 p. 



9 D. G. Deuel, Northeast Fisheries Center, Narragansett Laboratory, 

 Natl. Mar. Fish. Serv., NOAA, Narragansett, R.I., pers. commun. 

 September 1976. 



'"Christensen, D. J., B. L. Freeman, and S. E. Turner. 1976. The 



