European lobster subpopulations from limited adult movements and larval retention

Abstract

Øresland, V., and Ulmestrand, M. 2013. European lobster subpopulations from limited adult movements and larval retention. – ICES Journal of Marine Science, 70: 532–539. Adults and larvae of the European lobster, Homarus gammarus, were studied within and around the Swedish Kåvra lobster reserve (2.2 km2). Tagging of 4016 lobsters within the reserve showed that the lobsters have limited movement out of the reserve. Only 58 lobsters (1.4% of all tagged lobsters) were recaptured ≥1 km from the reserve and 5658 recaptures were obtained inside the reserve. Light trap catches showed that stage 1 larvae had a peak occurrence during <2 weeks, in early August, 2007–2009. The mean depth distribution of stage 1 larvae was 16 m and very few larvae were found in the low saline surface layer. No later stages were found in horizontal net tows. The lobsters inside the reserve provided stage 1 larvae to the nearby area. A persistent retention of water masses was found at 16-m depth (below the sharp halocline) in the area (16 km2) around the reserve using IMR GPS Current Drifters. In sharp contrast, surface drifters showed strong offshore and inshore movements. The Swedish archipelago might harbour many lobster and other decapod subpopulations, if the larval stages occur in a large proportion below the sharp halocline and if adult movements are limited.

Population genetic structure in European lobsters: implications for connectivity, diversity and hatchery stocking

“…Triantafyllidis et al (2005) previously detected significant broad-scale IBD among H. gammarus populations, and our results provide further evidence that dispersal may be restricted throughout the species' range. High site fidelity has been observed among adult lobsters across multiple locations (Øresland & Ulmestrand 2013, Wiig et al 2013, Skerritt et al 2015 and the pelagic larval duration is a relatively modest 2 to 4 wk under natural thermal niches (Schmalenbach & Franke 2010).…”

“…Several discrete H. gammarus subpopulations have been proposed in recent years via evidence of genetic or oceanographic isolation (Triantafyllidis et al 2005, Øresland & Ulmestrand 2013, or trait variation (Ellis et al 2015b), with extensive differentiation apparent between stocks as close as 142 km apart (Jørstad et al 2004). We aimed to investigate the fine-scale genetic structure of a lobster population around the Atlantic peninsula of Cornwall in the southwestern UK, where a regional stock en hancement programme collects ovigerous females to rear mixed batches of juveniles for wild release throughout a ~250 km section of coastal waters (Ellis et al 2015a).…”

Long-term decrease in sex-specific natural mortality of European lobster within a marine protected area

“…2) indicates that permanent emigration from the Kåvra MPA is probably limited and, hence, that apparent survival may be an adequate approximation of true survival. There is an active fishery for lobster in the archipelago near Kåvra from late September to the end of March, with peak intensity from late September to early December (Øresland & Ulmestrand 2013). Some lobster fishers operating in this and other areas along the Swedish west coast have kept and reported voluntary catch diaries throughout the study period (see Sundelöf et al 2013).…”

“…Some lobster fishers operating in this and other areas along the Swedish west coast have kept and reported voluntary catch diaries throughout the study period (see Sundelöf et al 2013). Based on a history of communication and cooperation between The Institute of Marine Research, Lysekil and local fishers, it is likely that the vast majority of recoveries have indeed been reported by fishers (Øresland & Ulmestrand 2013). We note that the 101 recoveries reported from outside MPA borders, which in fact constitute ≈7% of all recaptures, as quantified herein, are indicative of limited spillover from the Kåvra MPA.…”

“…The Kåvra MPA was created for research purposes with the objective of studying the development of a lobster population within a limited area in the absence of harvesting (see Øresland & Ulmestrand 2013). Specifically, we estimate sex-specific survival probability from a unique long-term capture-mark-recapture data set that was collected in the MPA from 1994 to 2007.…”