Delineation of Critical Inshore Spawning Grounds for Commercially Valuable Squid Fisheries on the East and West Coast of the USA
- Roger Hanlon
Marine Biological Laboratory
- Kenneth Foote
Woods Hole Oceanographic Institution
End Date: May 31, 2004
This project proposes to use the best available acoustic sampling technology (hardware, software, and sampling routines) to find and measure the areas of greatest concentration of benthic egg beds of the squids Loligo opalescens. The fishery is valued at ca. $30 to $33 million annually and both are estimated to be at or near maximum sustainable yield, yet much of the fishing takes place directly on sites of egg deposition, and is disruptive to either mate selection and egg laying or to the egg capsules themselves.
Squids live only 6-15 months and thus successful annual recruitment to the fishery is mandatory. Unlike other marine animals, squids offer a great advantage because they deposit egg capsules in large communal beds directly on the substrate. This feature allows a direct measure of reproductive success of these annual species, and provides a unique biological assay to assess annual recruitment potential.
The goals of this project are (i) to test and refine the acoustic technology to image and quantify the egg beds, and (ii) to determine the habitats with greatest concentration of egg beds. This technology (with refined methodology) and the biological information on critical spawning habitat will be provided to fishery and sanctuary managers, who will also acquire a tool for future monitoring and stock assessment.
Summary to DateThe market squid (Loligo opalescens) supports the largest commercial marine fishery in California, both in terms of quantity landed and dollars paid ex-vessel. The fishery is presently being managed without an estimate of population abundance, which is critical to establishing catch limits.
Preliminary findings from a cruise with in Monterey Bay, 5-12 May 2003, may change this situation by allowing quantification of the spawning products. Imaging the spawning grounds by means of sidescan sonar at 420 kHz has revealed characteristic markings that are very suggestive of the size and distribution of clumps of market-squid benthic egg beds, each composed of groups of gelatinous egg capsules.
The hypothesis that these are due to squid egg beds has been tested by means of video surveys conducted by scuba divers over comparable seafloor areas with and without egg beds. Evidence for the correspondence is presented. (Support by Sea Grant is acknowledged.)
Data are now being analyzed. Preliminary findings are being presented at scientific meetings, including Oceans 2003 and the 146th Meeting of the Acoustical Society of America.
- Habitat association
- Stock assessment
- Substrate characterization
- Sonar; echo data; underwater photography
Study MethodsVarious boats, acoustic hardware and software, underwater cameras, SCUBA equipment, and small ROVs are being used on the project. An essential tool is the Edgetech model 272-TD sidescan sonar towfish. Also being tried are Simrad EK60 Scientific Echo Sounder System and the RESON SeaBat model 8101 multibeam sonar. Vessel platforms include the R/V Mako and R/V MacGinitie. SCUBA diving is utilized to verify the presence of egg capsules being accoustically imaged.
Figures and Images
Squids spawning in Monterey Bay. Note the white squid egg beds distributed in the sand. The study objective is to map the distribution and abundance of egg beds using acoustic technology. Photo: Roger T. Hanlon