The Spot Prawn Fishery: A Status Report - Earth Economics

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The Spot Prawn Fishery: A Status Report Spot prawns typically inhabit rocky or hard bottoms, including reefs, coral or glass-sponge beds, and the edges of marine canyons. In part, species abundance is determined by the natural productivity levels characteristic of an area. Distribution is a function of the temperature and salinity of the water, and the animal’s developmental stage. Immature shrimp are able to tolerate greater ranges in both these factors and are found in shallower depths than adults. Common depth ranges extend from the intertidal to 487 meters (1,607 feet). Spot prawns are typically found at depth’s of between 198 and 234 meters (653–772 feet). Research carried out by Schlining (1999) investigates spot prawn habitat and distribution. Detailed examination of video transects in, close to, and outside an ecological reserve in the Monterey Bay area revealed that spot prawns are not simply distributed in the most commonly available habitat type. Although the nature or pattern of selection is unclear, active habitat selection seemed to be taking place. Habitat types associated with spot prawns varied by depth. Spot prawns were more commonly associated with complex habitats of mixed sediment and smaller rock types such as gravel and cobble. The animals were also associated with large aggregations of drift algae, where this existed. Distribution appeared to be very patchy. A finding that Schlining (1999) correlates with local trap fishers’reports suggests that spot prawns may be vulnerable to local overfishing and serial depletion (Orensanz 1998). The factors determining the size and location of patches are unclear, but are probably influenced by spot prawn habitat selection and larval transport (Lowry, University of Washington School of Fisheries. Pers. comm., May 2001). Juvenile spot prawns concentrate in shallow inshore areas (
The Spot Prawn Fishery: A Status Report spawning characteristically occurs earlier. Each animal spawns once as a male and once or more as a female. Spawning takes place at depths of 151–212 meters (500–700 feet). Female fecundity (number of eggs) is a function of the animal’s size and ranges from 1,400 to 5,000 eggs for the first spawning, approximately 1,000 for the second spawning. Females carry the eggs under their tails on appendages called swimmerets or pleopods. Fertilized and developing eggs are carried for four or five months, until they hatch, usually over a 10-day period. Upon hatching, the larvae enter a pelagic life stage in the water column. Larvae can remain free-swimming for up to three months, their movements potentially influenced by tides and currents (Boutillier and Bond 1999a). It is important to note that estimates of the larval stage vary considerably with geographic region. Spot Prawn Life History Diagram Courtesy Jim Boutillier, Fisheries and Oceans Canada 4
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The Spot Prawn Fishery: A Status Report - Earth Economics

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