Bay squid, continued 



Salinity - Adults and Juveniles: Salinity ranges for 

 juvenile and adult squid are 20-37% o , with the lower 

 lethal limit being 17.5%o (Hixon 1980a, Hixon 1980b, 

 Hendrix et al. 1981, Laughlin and Livingston 1982). 

 The salinity range reported by Benson (1982) for bay 

 squid is 5-35. 5%o, with a preference for >15%o. How- 

 ever, these lower reported salinities may have been 

 taken at surface rather than bottom waters where the 

 squid were collected. It is also considered possible that 

 squid make forays into lower salinity surface waters to 

 feed and then return to deeper waters where the 

 salinity is higher (Hendrix et al. 1981). 



Dissolved Oxygen: Evidence indicates that paralarval 

 bay squid are capable of adjusting to low concentra- 

 tions of dissolved oxygen (DO) (<2 mg/l), perhaps by 

 increasing oxygen uptake rates (Vecchione 1991b). 

 This may be an adaptation to survive the seasonally 

 hypoxic bottom water where the the bay squid spawns. 

 Adults have been observed in water with a DO content 

 of 0.7 mg/l (Vecchione and Roper 1991). 



Migrations and Movements : Bay squid migration and 

 abundance are regulated by temperature and salinity 

 (Benson 1982, Laughlin and Livingston 1982). Squid 

 move out of bays to a few miles offshore during 

 December and February to avoid the cooler tempera- 

 tures. They move back to the bays in the spring when 

 temperatures increase. The spring movement is also 

 related to salinity, spawning, and feeding (Hixon 1 980a, 

 Hixon 1980b, Laughlin and Livingston 1982). Bay 

 squid are able to move into bottom water layers which 

 are higher in salinity due to stratification conditions that 

 also result in hypoxic water layers (Vecchione 1 991 a). 

 It is considered likely that the bay squid takes up 

 oxygen in upper, more oxygenated water layers and 

 then dives into the bottom waters facultatively. This 

 could be a feeding or predator avoidance strategy 

 (Vecchione 1991a), or possibly a behavioral mecha- 

 nism for avoiding hypoosmotic stress in stratified wa- 

 ters (Hendrix et al. 1981). 



Reproduction 



Mode : The bay squid is gonochoristic, with separate 

 sexes. Transfer of sperm to the female is accom- 

 plished by means of a spermatophore and specially 

 adapted arms on the males. 



Mating/Spawning : Bay squid perform head-to-mantle 

 mating (Juanico 1983). A knob on the female mantle 

 wall is reportedly formed for the attachment of sper- 

 matophores. However, it has also been suggested that 

 this pad does not occur in virgin females, and is actually 

 a tissue response to the implanted spermatophores 

 (Vecchione pers. comm.). Duration of the spermato- 

 phore attachment and in what quality it can persist 

 while attached to the female is unknown (Juanico 



1983). In the northern Gulf of Mexico, spawning can 

 occur year-round at depths of 2-18 m with major peaks 

 from April to July and a lesser peak from October to 

 November (Juanico 1983, Hargis and Hanlon 1984). 

 In the northern Gulf of Mexico, bay squid eggs appear 

 to hatch throughout the year except during the coldest 

 months (Vecchione 1991b). Eggs are deposited on 

 sandy bottoms, sometimes within estuaries (Benson 

 1 982, Vecchione 1 991 b). In Galveston Harbor, Texas, 

 egg capsules have been reported attached to crab 

 traps so thickly as to make them useless (Vecchione 

 1991b). 



Fecundity : As many as 2000 eggs have been produced 

 in a single brood. With multiple broods, an estimated 

 1400-6350 can be produced by one female during a 

 breeding season (Hixon 1 980a). Eggs are enclosed in 

 a capsule, the number per single capsule is limited by 

 size of individual eggs and the size of the spawning 

 female's nidamental apparatus (Boletzky 1986). 



Growth and Development 



Egg Size and Embryonic Development : Eggs are con- 

 tained in clavate egg capsules that are between 1 and 

 13 cm long (Hall 1970). One end of the capsule is 

 bulbous and contains most of the embryos, and the 

 opposite end is narrow and appears to be an attach- 

 ment stalk. Capsules are not joined together, and are 

 apparently attached directly to bottom sediments. The 

 average number of eggs and embryos in a capsule is 

 69. Eggs, on the average, measure 1 .8 mm long by 1 .3 

 mm wide and are enveloped in a clear jelly-like matrix. 

 Total embryonic lifespan is estimated as 35 to 40 days 

 based on observed growth rates. Detailed descrip- 

 tions of embryonic development can be found in the 

 literature (Hall 1970, Hunter and Simon 1975). 



Age and Size of Larvae : The total length of a newly 

 hatched bay squid is about 3.8 mm. Morphology and 

 development of planktonic "paralarvae" are discussed 

 by Vecchione (1 982). Due to the ambiguity of the term 

 "larva" when applied to cephalopods, a new designa- 

 tion has been proposed (Young and Harman 1988). 

 Cephalopods in the first post-hatching growth stage 

 that are pelagic in near-surface waters during the day, 

 and that have a distinctively different mode of life from 

 that of older conspecific individuals are defined as 

 "paralarvae." Paralarvae appear to exist only in the 

 Teuthoidea and Octopoda groups of cephalopod mol- 

 luscs. 



Juvenile Size Range : Hixon (1 980) found growth among 

 individuals to be highly variable with averages in nature 

 of 8.6 and 7.9 mm/month for males and females 

 respectively. There was no significant differences in 

 growth rates recorded from nature and laboratory or 

 between sexes. 



51 



