In situ Monitoring of Longfin Inshore Squid Egg Deposition and Embryonic Development

Abstract

Knowledge of squid early life history is relatively poor despite its importance for fisheries management. The longfin inshore squid Doryteuthis pealeii (Lesueur, 1821) is a commercially important species harvested extensively along the northeastern United States continental shelf. To understand the effects of fishing and environmental variability on D. pealeii in an inshore spawning ground (Nantucket Sound, MA), egg deposition and embryonic development were monitored in situ at commercial fish weirs in spring and summer 2008 to 2016. Logbooks were maintained in which catch (including the presence of egg masses) and effort data for each weir were recorded daily. Seawater temperature was recorded using data loggers affixed to the weirs. Newly deposited egg masses were transferred to a mesh enclosure on an opportunistic basis and placed immediately adjacent to the weir to permit semiweekly retrieval and sampling. Samples (five randomly chosen “fingers” excised from a mass) were chilled and transported to a nearby wet lab for microscopic examination to determine embryonic development stage. Hatch timing was determined via direct observation of paralarvae emerging from egg masses and development time was calculated as the number of days between egg mass deposition and hatching. The timing and duration of egg mass deposition varied between years. Embryonic development time of 15 egg masses ranged from 12 to 34 days and generally decreased at warmer temperatures. In situ observations were consistent with the findings of laboratory studies of D. pealeii and other loliginid squids.