Female reproductive output in the squid Loligo pealeii: multiple egg clutches and implications for a spawning strategy

We examined actual and potential reproductive output with particular attention to the females' abilities to lay multiple clutches of eggs. Combining the results of 2 summer spawning seasons, 28 of 47 females that laid eggs in captivity produced substantial clutches (i.e., 5 or more egg capsules per clutch) at least twice. Multiply-ovipositing females exhibited a variety of patterns of oviposition, ranging from relatively small clutches at short intervals to large clutches several weeks apart. Actual reproductive output varied greatly between females. In both years, the number of egg capsules and ova laid showed a negative relationship with the combined mass of the ovary and oviduct at the time of death. Separate correlations between the number of ova laid and the combined number of oocytes and ova remaining in the reproductive tract at death revealed a similarly negative, although statistically weaker, relationship in both years. Most importantly the number of ova laid in captivity (mean = 11800 in 1993 and mean = 15 293 in 1998) exceeded the combined number of ova and oocytes remaining at death (mean ca 4500 in both years) by roughly 3 x, providing an indication of the extent to which only counting remaining oocytes and ova can underestimate fecundity. The ages of ovipositing females spanned 4 to 6 mo, Interestingly, neither age nor mantle length consistently affected reproductive output, i.e., short young females could be just as fecund as longer older females. A supplementary feeding experiment failed to demonstrate an effect of feeding regime on captive Lifespan or reproductive output. The females in one year (1998) were maintained in isolation without access to males; these females laid fertilized eggs, some over periods of 15 or more days, demonstrating the use of stored sperm. For females that had oviposited in both years, the oocytes remaining in the ovary always ranged greatly in size and structure. Thus, the 'spawning strategy' of Loligo pealeii appears to involve multiple ovipositions over weeks or months, with oocytes possibly being developed continually. Placing the results of this study in a larger context, reproduction by females in this and other loliginids most likely entails copulation with multiple males and the laying of multiple clutches of eggs, possibly in different locations.