Consequences of environmental variability for spawning and embryo development of inshore market squid Doryteuthis opalescens .

摘要

Doryteuthis opalescens aggregate and migrate to the continental shelf during the last stage of their life presumably to select spawning sites that optimize the survival and fitness of their offspring. This dissertation examined the timing and site selection of spawning aggregations, and essential habitat requirements for their embryos. Squid embryos occurred every year for five years, across all seasons during most years (Winter 2009-Summer 2013) and were commonly observed to occur on coarse sands and on submarine canyon walls. Essential embryo habitat was defined by observed depth (10-100 m depth), embryo density (0.1-350.1 capsules·m-2), area (0.15-7.32·106m2), by repeated use, and by association with high O2 and pH (and low pCO 2). ROV observations of embryos recorded O2 from 70-280 microM, pH from 7.65-8.10, T from 9.8-18.1 °C, and S from 33.3-33.9 PSU and that O2, pH and T were higher (and S lower) in areas where embryos were present. Embryos exposed to combined low pH and low O2 in the laboratory had a 16.7 % longer development time, remained at earlier development stages and had 54.7 % smaller statolith area. Embryo dorsal mantle length and statoliths were bigger and yolk reserves were smaller in a low pH only laboratory treatment relative to those in a low O2 only treatment. Geochemical testing for pH and O2 effects evaluated element ratios (B:Ca, Mg:Ca, Sr:Ca, Ba:Ca, Pb:Ca, U:Ca) of embryonic statoliths. Uranium:Ca was eight-times higher in statoliths exposed to low pH and low O 2 than those exposed to high pH and O2.;This thesis provides evidence that squid spawn and hatch continuously on the SCB, that adults select sites that are exposed to relatively higher O2 and pH, embryos develop poorly when exposed to low O2 and pH, and that embryo statolith geochemistry can reflect sublethal levels of O2 and pH. Several options are available for inclusion of climate change into adaptive management policy including mapping and monitoring embryo habitat over the range of D. opalescens and development of research initiatives inclusive of commercial fishers.