Variability of egg escapement, fishing mortality and spawning population in the market squid fishery in the California Current Ecosystem

Abstract

With an average yield of 70 000 Mt from 1999 to 2006, market squid (Doryteuthis opalescens) represents one of the most commercially valuable and biologically productive populations off California. An egg escapement model was developed for evaluating the population’s reproductive response to varying levels of fishing pressure and, potentially, for aiding management of the fishery. The model is founded on eggs-per-recruit theory, assuming catch fecundity is related to daily-based fishing mortality (F), i.e. analysis generated estimates of proportional egg escapement, S(F), as a function of F per quarter from 1999 to 2006 in three spawning grounds off northern and southern California. Fishing pressure was generally high, with mean derived F ranging from 0.20 to 6 per day. Mean estimated S(F) ranged from 0.08 to 0.75, but in most quarters was higher than 0.30. The classical model was extended for estimating absolute abundance of the resource based on F. Market squid were more abundant in southern California, where mean spawning stock peaked at 1.50 × 109 females, ~108 000 and 130 000 Mt in autumn 2000 and winter 2005 respectively. Although time demanding, this per-recruit analysis represents an effective approach for monitoring reproductive outputs and for aiding stock status determinations of harvested market squid.

Environmental pH, O2 and Capsular Effects on the Geochemical Composition of Statoliths of Embryonic Squid Doryteuthis opalescens

“…This includes assessment of their population connectivity [30], as well as knowledge of critical ecological mechanisms controlling their population size [31]. Fishery boom and bust cycles often correlate with environmental change, such as that associated with ENSO [27][28][29].…”

Predicting market squid (Doryteuthis opalescens) landings from pre-recruit abundance

“…Management measures for the fishery at the time of this manuscript include an annual catch limit of 107,048 mt (based on the highest catches reported prior to adoption of the management plan), limited entry into the fishery, weekend closures to provide for periods of uninterrupted spawning, lighting restrictions, and development of monitoring programs that include port sampling and logbooks (Leos, 1998;CDWF (California Department of Fish and Wildlife), 2005). Port sampling data have been used to assess the magnitude of fishing mortality and spawning population abundance based on an egg-escapement method, in which the relative fraction of potential oocytes (eggs) released from fishery-captured females harvested on their spawning grounds is compared to the spawning potential had no squid been captured (Macewicz et al, 2004;Maxwell et al, 2005;Dorval et al, 2013). While these methods lead to insights that can provide a strong overall basis for management, results are not available until well after the fishery is prosecuted.…”

“…We develop indices of abundance of pre-recruit market squid, as well as a key market squid prey item (krill), based on data collected in a midwater trawl survey that was designed to estimate the abundance of young-of-the-year pelagic juvenile rockfish (Ralston et al, 2013), but using methods comparable to those used to implement pre-recruit surveys in other cephalopod fisheries (e.g., Kidokoro et al, 2014). We evaluate their potential to inform near-term forecasts of squid abundance by comparing the indices to regional catches and to biomass estimates that were hind-casted using the egg escapement method of Dorval et al (2013). Our objective is to evaluate whether survey indices are sufficiently informative as to provide some value as a pre-recruit index for either fishery participants or fisheries managers relative to near term expectations of resource productivity.…”

Oceanographic influences on the distribution and relative abundance of market squid paralarvae (Doryteuthis opalescens) off the Southern and Central California coast

“…Market squid die within days after spawning (Macewicz, Hunter, Lo, & LaCasella, ) and the life cycle is complete within 1 year (Butler, Fuller, & Yaremko, ). Market squid populations fluctuate tremendously (Dorval, Crone, & McDaniel, ), and warm (El Niño) and cool (La Niña) phases of the El Niño Southern Oscillation (ENSO) are considered to be a major influence (Koslow & Allen, ; Reiss, Maxwell, Hunter, & Henry, ).…”

“…Market squid populations fluctuate tremendously (Dorval, Crone, & McDaniel, 2013), and warm (El Niño) and cool (La Niña) phases of the El Niño Southern Oscillation (ENSO) are considered to be a major influence (Koslow & Allen, 2011;Reiss, Maxwell, Hunter, & Henry, 2004).…”