306 



Abstract— Loligo opalescens live less 

 than a year and die after a short 

 spawning period before all oocytes are 

 expended. Potential fecundity iE P ), 

 the standing stock of all oocytes just 

 before the onset of spawning, increased 

 with dorsal mantle length (L), where 

 E P = 29. 8L. For the average female 

 squid (L of 129 mm), E P was 3844 

 oocytes. During the spawning period, 

 no oogonia were produced: therefore 

 the standing stock of oocytes declined 

 as they were ovulated. This decline in 

 oocytes was correlated with a decline 

 in mantle condition and an increase 

 in the size of the smallest oocyte in 

 the ovary. Close agreement between 

 the decline in estimated body weight 

 and standing stock of oocytes during 

 the spawning period indicated that 

 maturation and spawning of eggs could 

 largely, if not entirely, be supported 

 by the conversion of energy reserves 

 in tissue. Loligo opalescens, newly 

 recruited to the spawning population, 

 ovulated about 36^ of their potential 

 fecundity during their first spawning 

 day and fewer ova were released in 

 subsequent days. Loligo opalescens do 

 not spawn all of their oocytes; a small 

 percentage of the spawning population 

 may live long enough to spawn 78% of 

 their potential fecundity. 



Loligo opalescens are taken in a 

 spawning grounds fishery off Califor- 

 nia, where nearly all of the catch are 

 mature spawning adults. Thirty-three 

 percent of the potential fecundity of 

 L. opalescens was deposited before they 

 were taken by the fishery (December 

 1998-99). This observation led to the 

 development of a management strategy 

 based on monitoring the escapement 

 of eggs from the fishery. The strategy 

 requires estimation of the fecundity 

 realized by the average squid in the 

 population which is a function of egg 

 deposition and mortality rates. A model 

 indicated that the daily total mortality 

 rate on the spawning ground may be 

 about 0.45 and that the average adult 

 may live only 1.67 days after spawning 

 begins. The rate at which eggs escape 

 the fishery was modeled and the sen- 

 sitivity of changing daily rates of fish- 

 ing mortality, natural mortality, and 

 egg deposition was examined. A rapid 

 method for monitoring the fecundity of 

 the L. opalescens catch was developed. 



Manuscript approved for publication 

 19 December 2003 by Scientific Editor. 



Manuscript received 20 January 2004 

 at NMFS Scientific Publications Office. 

 Fish. Bull. 102:306-327 (2004). 



Fecundity, egg deposition, and mortality of 

 market squid (Loligo opalescens) 



Beverly J. Macewicz 



1. Roe Hunter 



Nancy C. H. Lo 



Erin L. LaCasella 



Southwest Fisheries Science Center 



National Marine Fisheries Service, NOAA 



8604 La Jolla Shores Drive 



La Jolla, California 92037-1508 



E-mail address (for B J. Macewicz): Bev Macewiczi5noaa.gov 



Many loliginid squid populations 

 depend entirely upon the reproduc- 

 tive output of the preceding genera- 

 tion because individuals live less than 

 a year (Yang et al., 1986; Hatfield, 

 1991, 2000; Natsukari and Komine, 

 1992; Arkhipin, 1993; Arkhipin and 

 Nekludova, 1993; Jackson, 1993, 1994; 

 Jackson et al., 1993; Boyle et al., 1995; 

 Jackson and Yeatman, 1996; Jackson 

 et al., 1997; Moltschaniwskyj and Sem- 

 mens, 2000; Semmens and Moltschani- 

 wskyj, 2000). In California waters, 

 Loligo opalescens (market squid, also 

 known as the opalescent inshore squid 

 [FAO]) live only 6-12 months (Butler 

 et al., 1999) and die after spawning 

 (McGowan, 1954; Fields, 1965). Thus, 

 fecundity of L. opalescens is a criti- 

 cal life history trait and, in addition, 

 must be known in order to estimate the 

 biomass with either egg deposition or 

 larval production methods (Hunter and 

 Lo, 1997). Loligo opalescens is one of the 

 most valuable fishery resources in Cali- 

 fornia waters and is monitored under 

 the Coastal Pelagics Species Fishery 

 Management Plan of the Pacific Fishery 

 Management Council as market squid. 

 Laptikhovsky (2000) pointed out 

 that squid fecundity estimates would 

 be biased if the females spawned ova 

 prior to capture, if oocytes remained 

 in the ovary after death, or if some of 

 the standing stock of oocytes were lost 

 because of atresia. Previous field work 

 on squid fecundity has been limited to 

 the traditional method of simply count- 

 ing oocytes or ova (or both) of animals 



taken on the spawning grounds, and 

 none of the biases identified by Lap- 

 tikhovsky (2000) have been evaluated 

 (Boyle and Ngoile, 1993; Coelho et al., 

 1994; Guerra and Rocha, 1994; Boyle et 

 al„ 1995; Collins et al., 1995; Moltscha- 

 niskyj, 1995; Lopes et al., 1997; Lap- 

 tikhovsky, 2000). On the other hand, 

 laboratory studies (Ikeda et al., 1993; 

 Bower and Sakurai, 1996; Sauer et al., 

 1999; and Maxwell and Hanlon, 2000) 

 have indicated that oocytes remain in 

 the ovaries after spawning and death. 

 Additionally, atresia was found to oc- 

 cur in all stages of oocytes of Loligo 

 vulgaris reynaudii (Melo and Sauer, 

 1998). Modern approaches to estimat- 

 ing lifetime fecundity in fishes take 

 the potential biases of past spawning 

 history, residual fecundity, and atresia 

 into account (Hay et al., 1987; Hunter 

 et al., 1992; Macewicz and Hunter. 

 1994; Kjesbu et al., 1998). The initial 

 objectives of the present study were to 

 estimate the fecundity of L. opalescens 

 by using a modern approach that con- 

 siders such biases, and to provide a 

 histological description of those aspects 

 of ovarian structure upon which mod- 

 ern fecundity analyses are based. As 

 our work progressed, we realized that 

 it might be practical to manage the 

 market squid fishery by monitoring egg 

 escapement based on fecundity mea- 

 surements. Thus, we added two new 

 objectives: to conduct a preliminary 

 evaluation of the use of egg escapement 

 as a tool for management of the market 

 squid fishery; and to develop a method 



