Abstract
Crustaceans are key components of marine ecosystems which, like other exploited marine taxa, show seasonable patterns of distribution and activity, with consequences for their availability to capture by targeted fisheries. Despite concerns over the sustainability of crab fisheries worldwide, difficulties in observing crabs’ behaviour over their annual cycles, and the timings and durations of reproduction, remain poorly understood. From the release of 128 mature female edible crabs tagged with electronic data storage tags (DSTs), we demonstrate predominantly westward migration in the English Channel. Eastern Channel crabs migrated further than western Channel crabs, while crabs released outside the Channel showed little or no migration. Individual migrations were punctuated by a 7-month hiatus, when crabs remained stationary, coincident with the main period of crab spawning and egg incubation. Incubation commenced earlier in the west, from late October onwards, and brooding locations, determined using tidal geolocation, occurred throughout the species range. With an overall return rate of 34%, our results demonstrate that previous reluctance to tag crabs with relatively high-cost DSTs for fear of loss following moulting is unfounded, and that DSTs can generate precise information with regards life-history metrics that would be unachievable using other conventional means.
Highlights
Obtaining frequent, repeated and accurate estimates of the location of marine animals and an accompanying description of spatial and temporal behaviour patterns has for many years presented marine scientists with a significant technical challenge [1]
Detailed information on habitat use can be gained from acoustic or ultrasonic tracking [22,23,24], but spatial coverage is limited and precision can be adversely affected by seabed features and can be lost altogether when the animal moves into a crevice or burrow
Previous mark-recapture studies have suggested that migration by male edible crab is limited [33,23], to maximise viable return rates, only female crab have been targeted in this study
Summary
Obtaining frequent, repeated and accurate estimates of the location of marine animals and an accompanying description of spatial and temporal behaviour patterns has for many years presented marine scientists with a significant technical challenge [1]. This challenge has been partially addressed in recent years for large to medium-sized marine vertebrates Progress with archival tagging in particular has significantly advanced understanding of the spatial structure and population dynamics of fishes, including smaller, sea-bed dwelling species including flatfish Electromagnetic telemetry operates at a local scale over short time periods and studies are limited by the short range of detection and the requirement for cables on the seabed [25,26,27]
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