Adaptations for cold water spawning in loliginid squid: Loligo Gahi in falkland waters

摘要

Inshore spawning sites of the cold water squid Loligo gahi were found in the waters of East Falkland (Southwest Atlantic), where there is a major fishery based on this species. Egg masses occurred in algal beds, often at the outer (seaward) edge, with ambient water temperatures of 6.5-9 deg C and salinity 33.75-33.85per thousand. They were attached to the stipes of the kelp algae Lessonia spp. and Macrocystis pyrifera from 0.5 m to 2.5 m off the bottom at 8-20 m depths. The overall density of egg masses was low. The egg mass is a bundle of elongated gelatinous translucent capsules with each capsule firmly attached to the kelp stipe at its basal end. The capsules are mainly 50-60 mm in length and contain an average of 70 fertilized eggs. Sampled egg masses consisted of 4-161 capsules and from 138 to 11,487 eggs. Large egg masses (> 50 cap-sules) were apparently formed by several females at different times, as embryos in different capsules were at various stages of development. Eggs laid in winter are significantly larger than those laid in summer. In comparison with tropical and temperate Loligo spp. L. gahi have short egg capsules containing a small number of eggs, but the eggs (2.2-2.5 mm diameter) and hatchlings (3.1-3.4 mm mantle length) are large. These are probable adaptations for cold water spawning and development.