Spatially structured interactions between lobsters and lobster fishers in a coastal habitat: fine-scale behaviour and survival estimated from acoustic telemetry

Abstract

Abstract:Fishing can have profound impacts on the ecology and evolution of marine populations. Understanding populationlevel changes ultimately depends on knowledge about individual survival and how it varies in time and space. We used acoustic tags and a network of receivers to monitor individual behaviour and fate of European lobster (Homarus gammarus) exposed to commercial and recreational trap fisheries on the Norwegian Skagerrak coast. In August 2011, 50 male lobsters above minimum legal size were tagged and monitored before and during the lobster fishing season. We also quantified the spatial and temporal variation in fishing activity. There was no significant effect of home-range size on the probability of surviving the fishery. However, there was substantial fine-scale spatial variation in fishing activity, and lobsters with short-term home ranges positioned away from trap-dense areas had a significantly higher survival probability. Also, the overall survival probability of 16.7% suggests that fishing depletes the catchable lobster population at a high rate. The current harvesting regime may drive selection in favour of movement behaviours avoiding habitats typically targeted by fishers.Résumé : La pêche peut avoir des lourds impacts sur l'écologie et l'évolution des populations marines. La compréhension des changements à l'échelle de la population dépend des connaissances sur la survie des individus et les variations de cette dernière dans le temps et l'espace. Nous avons utilisé des marqueurs acoustiques et un réseau de récepteurs pour surveiller le comportement individuel et le destin de homards européens (Homarus gammarus) exposés à la pêche commerciale et récréative au piège le long de la côte norvégienne du Skagerrak. En août 2011, 50 homards mâles de taille supérieure au minimum légal ont été marqués et suivis avant et durant la saison de pêche au homard. Nous avons également quantifié les variations spatiales et temporelles des activités de pêche. Aucun effet significatif de la taille du domaine vital sur la probabilité de survie à la pêche n'a été noté. D'importantes variations spatiales fines des activités de pêche ont toutefois été observées, et les homards dont les domaines vitaux à court terme se situaient à distance des zones de forte densité de pièges présentaient une probabilité de survie significativement plus grande que celle des autres homards. En outre, la probabilité de survie globale de 16,7 % semble indiquer que la pêche est à l'origine d'un déclin rapide de la population exploitable de homards. Le régime d'exploitation actuel pourrait se traduire par la sélection préférentielle de comportements de déplacement permettant d'éviter les habitats typiquement ciblés par les pêcheurs. [Traduit par la Rédaction]

Fine-scale movement, activity patterns and home-ranges of European lobster Homarus gammarus

“…2). While there have been 4 previous studies tracking H. gammarus, that have successfully described diel ac tivity patterns (Smith et al 1998(Smith et al , 1999, differences between native and transplanted lobsters (van der Meeren 1997) and long-term movement and home-ranges (Moland et al 2011a, Wiig et al 2013, none of the previous approaches were capable of accurately defining movement, substrate-utilisation or differences be tween sexes. One of the strongest aspects of the present study, was the large sample size (n = 44), which lends itself to more accurate use of KDE for home-range estimation (Mill spaugh & Marzluff 2001).…”

“…Previous studies report larger H. gammarus home-range estimates; Wiig et al (2013) Table 3. Mean (± SE) home-range statistics for lobsters observed during both periods (n = 10); 50% and 95% utilisation distribution (50UD and 95UD) area and substrate hardness whereas here we focussed on short-term, fine-scale movement within a restricted study area.…”

“…Despite the obvious advantages, AT has not yet been applied to crustaceans in the UK (Guerra-Castro et al 2011), where movement and space-utilisation remain poorly investigated (but see Smith et al 1998Smith et al , 2001. AT and data storage tags have been applied to H. gammarus on 3 occasions in Norway (van der Meeren 1997, Moland et al 2011a, Wiig et al 2013). However, the fishery, biological parameters and environmental conditions are quite different between the UK and Norway.…”

“…However, limitations of VRAP and the small sample size (n = 4) restricted the conclusions of the study. Two recent studies in Norway (Moland et al 2011a, Wiig et al 2013) utilised AT to elucidate long-term home-ranges of lobsters; these studies provide valuable data but were unable to provide detail of habitat-utilisation or movement.…”

“…(1) lobster home-ranges and movements were restricted to hard substrate; (2) the greatest space-utilisation and distances travelled were displayed by large, male lobsters, based on previous findings suggesting males are more 'risk-taking' and the weak positive relationship between size and distance travelled (Jensen et al 1994, Rowe 2001, Smith et al 2001, Wiig et al 2013; and (3) movement and space-use vary between seasons and over the diel cycle, with dark and warm periods leading to greatest movements.…”