Abstract
Knowledge about the spatial patterns and movements of crustaceans has gained importance since the creation of marine protected areas and the development of spatial management for benthic ecosystems. The Juan Fernández spiny lobster (Jasus frontalis) is an endemic marine species and most valuable resource that exhibits migratory dynamics in a highly spatially regulated fishery. To study movement patterns around Alexander Selkirk Island, a mark-recapture program was implemented in 2008, when approximately 7000 non-commercial (undersized) lobsters were tagged and followed for nearly 14 months. Using quantitative georeferenced data, this study revealed spatial structuring of Juan Fernández spiny lobster and tested hypotheses about alongshore and inshore-offshore movements. Eight clusters were identified around Alexander Selkirk Island, with moderate time-varying connectivity between them. Seasonal inshore-offshore movements were detected all around the island, but more conspicuously to the north. Average travelling distance was 1.2 km (1.7 sd). Our results confirmed that towards the end of austral spring males and females embark in a seasonal offshore migration to deeper waters, returning to shallower waters only during winter. These findings quantitatively consolidate the conceptual migratory model that local fishermen had already inferred for this resource from about a century of sustainable fishing.
Highlights
The distribution and movements of benthic marine resources constitute important aspects of population dynamic studies [1]
Return migrations in the winter season to deeper waters may be an escape from the wave turbulence and cold water temperatures that are frequent in shallow waters during the winter season [14]; in southern Gulf of Maine, ovigerous lobsters tracked with ultrasonic telemetry showed a movement pattern to offshore areas during winter, where they appeared to remain until after their eggs hatched in early summer [15]
We investigate the spatial structure of J. frontalis around Alexander Selkirk Island using georeferenced data on individual discrete fishing spots and we analyzed its alongshore and inshore-offshore migration using recapture data from an intensive biological sampling program
Summary
The distribution and movements of benthic marine resources constitute important aspects of population dynamic studies [1]. In clawed lobsters (Nephropidae) migratory patterns have been documented for Homarus americanus; in New England, movement was inshore in spring and summer returning offshore in fall and winter This movement is presumably promoted by the high temperatures in shallow waters during the summer season, which could favor reproductive processes such as molting, mating and spawning in females. In the family Scyllaridae, there is evidence of a seasonal pattern of adult lobsters Scyllarides latus that move to deeper-cold waters in midsummer, triggered by the high temperatures (28 ̊C-29 ̊C) registered in coastal regions [16,17] Brachyuran crabs exhibit seasonal and reproductive migrations [9]; Chionoecetes opilio undergo an ontogenetic migration in which older individuals move to deeper waters and return to shallow waters to mate with older multiparous females Females start their movement after the puberty molt and primiparous mating occurs during boreal winter and hatching takes place after a year. While the general movements are relatively well known in many large crustaceans, there are some others in which this process is only poorly understood, especially the seasonal movement patterns
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