FISHERY BULLETIN: VOL. 87, NO. 3, 1989 



Table 6. — Listing of instantaneous larval growth rates per day and water tempera- 

 tures (°C) from laboratory growtfi studies and linear regression analysis. 



<,>i - t, = bilnLi+i - In L,)/G„,. 



Then Z,, the instantaneous mortality rate per 

 day, where f, + i - f, equals one day, is calcu- 

 lated as 



Z, = (InNo - In N,)/t 



based on 



Nt = Noe 



-zt 



where A^o is number at Lq and A'^^, adjusted for 

 stage duration, is number at L,. G„. for each 

 species was estimated from the gi'owth rate - 

 temperature relationship in Table 6. The 

 length-weight exponent (b) was estimated as the 

 mean regression coefficient for seven species in 

 Laurence (1979) at 4.15 (SE = 0.14). G,„ and Z, 

 were calculated for 26 taxa and are shown in 



Table 5. The equation relating mortality (Z,) to 

 temperature (T) is 



Z, = -0.2722 + 0.01015 T 



r^ = 0.80 Sy.x = 0.0380. 



As mentioned above, the ratio of growth rate to 

 mortality rate must exceed one and as Ware 

 (1975) estimated from three data points, the 

 ratio of mortality to growth is near 0.7. The 

 slope of the linear regi'ession for the species in 

 Table 5 is 0.820. Five taxa are near or greater 

 then a ratio of one (i.e., mortahty > gi'owth): 

 Atlantic mackerel, Sebastes spp., haddock, cun- 

 ner, and bluefish (Fig. 6). The mortahty rates 

 calculated for these taxa are suspect and may 

 represent excessive net avoidance by the larger 

 larvae. When these taxa are eliminated from the 

 data the slope is 0.760 (SE = 0.051, n = 22). The 



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