FISHERY BULLETIN: VOL. 75, NO. 1 



noted that an anomalous peak occurs in 1970, 

 which examination of biomass estimates on a per- 

 species basis revealed to have been caused by 

 anomalously high mackerel catches in certain 

 tows during the 1969 survey. The influence of this 

 factor appears to have been compensated for by 

 use of the logarithmic transformation (Figure 13). 

 On the other hand, the anomalously low data point 

 for 1965 (Figures 12, 13) appears to have been 

 caused by anomalously low catches of herring in 

 that year, a circumstance in which the trans- 

 formation was ineffective. It does appear, how- 

 ever, that by and large the transformation was of 

 definite value in following trends through time, 

 although estimates for most of the years consid- 

 ered proved to be similar. 



The above analyses clearly indicate that 

 biomass levels have decreased significantly in SA 

 5 and 6 in recent years; the trend observed cor- 

 relates well with increases in fishing effort ob- 

 served by Brown et al. (in press). In addition, we 

 have also found evidence indicating that major 

 changes in species composition have occurred as 

 well. The apparent increase in white hake 

 abundance in the Gulf of Maine in recent years 

 (Table 5) could have resulted from population 

 increases in response to reductions in other 

 groundfish species. Similarly, increased mackerel 

 abundance coincident with declining abundance 

 of herring (Tables 3, 4) may indicate some form of 

 species interaction coincident with exploitation, 

 while apparent increases in abundance of squid 

 (Tables 2-7, Figure 9) may have occurred in re- 

 sponse to declining abundance of finfish species. 

 The relationships involved are unclear at present 

 and further study is obviously necessary. 



Comparisons of annual landings data since 197 1 

 (over 1.0 x 10 6 tons) with biomass estimates in 

 Tables 13 and 14 indicate that the fraction of the 

 biomass harvested annually has increased sig- 

 nificantly in recent years (i.e., from less than one- 

 fifth of the total in the early and mid-1960's to 

 between one-third and one-half of the total at 

 present). Furthermore, landings since 1971 have 

 exceeded the composite MSY figure of 950 x 10 3 

 tons calculated by Brown et al. (in press) based on 

 the Schaeffer yield model. This information, 

 together with declines in stock size approximating 

 50% as indicated in this paper, imply that a 

 significant degree of overfishing has occurred and 

 that stock size has been reduced below the level 

 corresponding to MSY. Back-calculations for all 

 species in Tables 13 and 14 provide an average 



stock size estimate of approximately 7.0 x 10 6 tons 

 prior to 1964, from which (allowing for the U.S. 

 coastal fishery in previous years) it may be in- 

 ferred that the actual virgin biomass for this 

 fishery probably approximated 8.0-9.0 x 10 6 tons. 

 Since the Schaeffer yield model postulates that 

 MSY will be taken at a stock level corresponding 

 to one-half the maximum (Schaeffer 1954), we 

 may in turn assume that a stock level of ap- 

 proximately 4.0-4.5 x 10 6 tons should be main- 

 tained for SA 5 and 6 if MSY from this resource is 

 to be achieved. In contrast, estimates for fishable 

 biomass in the present paper approximate 2.0 x 

 10 6 tons at the start of 1975, implying that a 

 lengthy period of reduced exploitation is necessary 

 if stocks are to be rebuilt to the MSY level. 



In April 1975, the Assessments Subcommittee 

 (STACRES) reviewed evidence relating to de- 

 clines in biomass in SA 5 and 6 in recent years and 

 concluded that substantial reductions in catch 

 would be necessary if stocks are to recover (In- 

 ternational Commission for the Northwest At- 

 lantic Fisheries 1975c). Accordingly, a TAC of 650 

 x 10 3 tons was recommended to ICNAF and 

 approved at the Seventh Special Commission 

 Meeting (International Commission for the 

 Northwest Atlantic Fisheries 1975b) in Sep- 

 tember. Even with a reduction of this magnitude, 

 STACRES estimated that a minimum of 7 yr 

 would be required for this resource to recover to 

 the MSY point. 



ACKNOWLEDGMENTS 



We thank Judith Brennan for her helpful 

 comments and suggestions on data analysis, 

 Kathryn Paine for her assistance with computer 

 programming, and Elizabeth Bevacqua and 

 Maureen Romaszko for numerous tabulations of 

 the data. Richard C. Hennemuth reviewed the 

 manuscript and made suggestions for im- 

 provement. The work of the numerous biologists 

 and technicians who have participated in Alba- 

 tross IV autumn bottom trawl surveys and the 

 processing of the sample data since the beginning 

 of the program is also sincerely appreciated. 



LITERATURE CITED 



ANTHONY, V. C, AND H. C. BOYAR. 



1968. Comparison of meristic characters of adult Atlantic 

 herring from the Gulf of Maine and adjacent waters. Int. 

 Comm. Northwest Atl. Fish. Res. Bull. 5:91-98. 



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