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Fishery Bulletin 102(2) 



Probably very few females would be expected to survive 

 six days because only a small percentage of the spawning 

 population (Table 4) met the mantle criteria for minimum 

 residual fecundity. 



In summary, our best guess of the maximum longevity 

 of squid on the spawning grounds is about six days. Our 

 best description of daily egg deposition is a rate that ends 

 the first day with 36% of the potential fecundity deposited 

 and averages about 9% of the potential per day over the 

 remaining five days and where only a small percentage 

 of the females live to deposit 78% or more of their poten- 

 tial fecundity. 



Egg escapement 



We examine the spawning dynamics of Loligo opalescens 

 from the standpoint of possibly using fecundity of the 

 catch to monitor and ultimately regulate escapement of 

 eggs from the fishery. The key variable in this approach 

 is the fraction of the potential fecundity that is actually 

 deposited as eggs on the bottom because this value can be 

 directly estimated from the fecundity of the catch. Two 

 other important parameters are the daily rate of total 

 mortality (2) on the spawning grounds and the daily rate 

 of egg deposition (y). Neither of these parameters can be 

 directly estimated but they are approximated by values 

 that are most consistent with our observations by using 

 a model (Eq. 1). Our observations consist of the fecundity 

 of the catch and the inferences regarding longevity and 

 egg deposition, presented in the previous section. We use 

 our approximations for egg deposition and total mortality 

 in a second model (Eq. 12) to gain an idea of how natural 

 mortality and fishing mortality may affect egg escape- 

 ment. Lastly, we present a rapid method for monitoring 



the fecundity of the catch which does not require direct 

 counting of oocytes or ova. 



Fraction of the potential fecundity spawned (Q 5P ) In a 

 spawning population of L . opa lescens, the mean standing 

 stock of oocytes and ova (E YD ), when expressed as a frac- 

 tion of potential fecundity, is equivalent to the fraction 

 of the potential f ecundity of the population that remains 

 i n the sp awners (E YD IE P ). When subtracted from one (1- 

 [Ey D /E P ] ), the difference becomes the fraction of the poten- 

 tial fecundity of the population that is actually spawned 

 (Qsp). For this interpretation to be correct, samples must 

 be randomly drawn from the population and represent all 

 spawners according to their abundance on the spawning 

 grounds — from the newly recruited to those that have 

 been spawning for extended periods. 



Neither the females taken from our research cruises nor 

 those used to estimate fecundity from the landed catch 

 were random samples of the spawning population. First, 

 not all of the specimens taken during the two research 

 cruises were from the spawning grounds. Second, the 60 

 females from the commercial catch were not randomly 

 chosen but were selected to represent a full range of L 

 and C. However, by weighting our fecundity estimates by 

 a random sample of mantle condition from the fishery, it 

 was possible to approximate a random fecundity sample of 

 spawners. The population we used for weighting was based 

 on the mantle condition index (C) of 1275 randomly taken 

 specimens from the commercial catch sampled December 

 1998 through December 1999 (Table 4). The weighted 

 and unweighted mean standing stocks of oocytes and ova 

 (E YD ) were similar (Table 5), indicating that our previous 

 selection of specimens by C did not introduce a large bias. 

 For the unweighted data, E YD was 2541 and was 2599 



