Terceiro and Idoine: SRLCA application to Pand^lus borealis survey data 



767 



Table 3 



Von Bertalanffy growth parameter pairs ami SRLCA score 

 (S) for 1986 northern shrimp survey length-frequency distrilju- 

 tion: primary and secondary ridge crests. 



' High score parameters of ridge crest, on boundary of ex- 

 plored space. 



- High score parameters of ridge crest, nonboundary max- 

 imum. 



'Parameters selected for final evaluation. 



last mode interpreted as age-3 shrimp. Tlie secondary 

 ridge high-score parameters classified the first, second, 

 and fourth observed modes fairly well, with the highest 

 scoring parameters (L„,f = 33 mm, K = 0.42) falling in 

 an interval between previously estimated von Ber- 

 talanffy parameters. SRLCA was thus able to match 

 the a priori interpretation of the 1986 length-frequen- 

 cy distribution reasonably well, using parameters from 

 the secondary ridge crest (Fig. 8). 



1 987 distribution The first mode of this distribution 

 is fairly pronounced and has been interpreted as age 1 , 

 but the modes following are not well defined (NSTC 

 1987; Fig. 2). SRLCA indicated best fitting parameter 

 pairs in a primary score ridge ranging from Linf = 35 

 mm, K = 0.50 to Li„f= 50 mm, K = 0.23, with a max- 

 imum at Ljnf = 40 mm, K = 0.36, and in a secondary 

 ridge ranging from Ljnf = 32 mm, K = 0.50 to L,„f = 

 40 mm, K = 0.24, with a nonboundary local maximum 

 at L,nf = 33 mm, K = 0.43 (Table 4, Fig. 9). The pri- 

 mary ridge parameters defined three age groups, 

 correctly classifying the first mode, lumping shrimp 

 between 19.0 and 25.0 mm as a second group, and 

 aggregating all shrimp >25 mm as a final group. The 

 secondary ridge parameters resolved the distribution 

 in a similar manner, but by splitting shrimp >23 mm 

 into two groups (Fig. 10). Thus, neither set of param- 

 eters selected by SRLCA successfully resolved shrimp 

 between 19.0 and 25.0 mm to distinct cohorts. 



1 988 distribution In the 1988 survey length frequen- 



1986 DISTRIBUTION 



Figure 7 



Response surface of the SRLCA score function for the northern 

 shrimp survey 1986 length-frequency distribution. 



o 



< 



1986 



80 



-60 



o 

 o 



UJ 



> 



5 



10 15 20 25 30 



CARAPACE LENGTH (mm) 



35 



Figure 8 



Northern shrimp survey 1986 length-frequency distribution (histo- 

 gram) and pattern of SRLCA scores (solid curve) for growth param- 

 eters selected for final evaluation (L , = 33 mm. K = 0.42). 



cy, the large mode between 13 and 19 mm was assumed 

 to be age-1 shrimp. A smaller mode of 20-23 mm was 

 interpreted as age 2, with shrimp >25 mm assumed, 

 as usual, to be age-group 4+ (NSTC 1988; Fig. 2). 

 SRLCA provided two ridges of high scoring param- 

 eters, a primar'y ridge extended from a boundary max- 



