Modelling larval dispersal of Pecten maximus in the English Channel: a tool for the spatial management of the stocks

Abstract

The great scallop Pecten maximus supports one of the most important and valuable commercial fisheries around the British Isles and in the northwest of France, but the resource is mainly managed at the scale of each local fishing ground through a combination of European, national and local measures. To analyse the larval dispersal pathways and connectivity patterns among fishing grounds of the great scallop in the Celtic Sea and the English Channel, a particle tracking model was developed. The model combined a 3D physical circulation model that simulated currents and temperature fields and a scallop larval submodel that took into account a temperature-dependent planktonic larval duration and an active vertical swimming behaviour. Due to the lack of stock assessment at the regional scale, the location of the main fishing grounds was established by combining different sources (e.g. grey literature, unpublished scientific surveys, vessel monitoring data, fishermen) while the spawning biomass of each stock was estimated from landings data. Results indicated that each local stock could not be considered as a single independent management unit and that all stocks except that of the Bay of Brest were connected to neighbouring stocks, suggesting that the management should be defined in a metapopulation context. Three major groups of strongly interconnected stocks including two or three stocks exhibiting high retention and self-recruitment rates and some peripheral stocks with a low self-recruitment rate were defined: the North Brittany and Channel Islands, the eastern English Channel, and the SW of England. Our results were discussed in terms of the definition of management units in comparison with genetic and phenotypic data, and in terms of resource management in a transnational context.

New insights on the population genetic structure of the great scallop (Pecten maximus) in the English Channel, coupling microsatellite data and demogenetic simulations

“…Previous estimates of P. maximus larval connectivity between the main scallop beds in the English Channel were obtained by the development of a Lagrangian biophysical model, which coupled a three‐dimensional hydrodynamic model and a biological submodel (Nicolle et al, 2013, 2016). The biological submodel considered a temperature‐dependent spawning time, a temperature‐dependent planktonic larval duration, and larval behaviour.…”

“…According to the model, larval dispersal occurs mainly among neighbouring sites located less than 100 km apart, whereas exchanges between the three groups are rare and weak. Within each group, two or three spawning units act as source populations with high retention and self‐recruitment rates, whereas peripheral beds act as sink populations with a low self‐recruitment rate (Nicolle et al, 2016). Moreover, the model found the Bay of Brest, located at the tip of Brittany, to be partially isolated from the English Channel.…”

“…Moreover, the model found the Bay of Brest, located at the tip of Brittany, to be partially isolated from the English Channel. Within a bed, year‐to‐year variations in environmental forcing are responsible for variation in the reproductive success of scallops and the origin of recruits (Nicolle et al, 2013, 2016).…”

The pace of life: Time, temperature, and a biological theory of relativity

“…More recently (and formally since [18]), the use has been expanded to aquatic animals with size-at-age and development timing explained on biological time for fish and invertebrates (e.g. [18], [19], [20] [21], [22], [23] [24], [25]). For example, we were able to use DD as a biological (thermal) time-scale that explains 93% of the variability in juvenile cod ( Gadus morhua ) size-at-age across the species’ range [18], as well as disentangle adaptive variability in reproductive timing across years and locations [21], [25].…”

The Decreasing Availability of Settlement Surfaces Affects the Transition From Larvae to Early Recruitment of the Scallop Argopecten purpuratus Through El Niño and La Niña Episodes

“…In Chile, studies on the ecology of early life stages of A. purpuratus are lacking, but larval settlement in artificial collectors differ between El Niño and La Niña episode (Cantillánez et al, 2007). As, e.g., larval growth, duration and mortality are temperature dependent-factors for pectinids species (Davies et al, 2015;Nicolle et al, 2016) and temperature regimes in La Rinconada may respond to El Niño and La Niña episodes, it is key to assess how temperature may affect the transition between larval release and subsequent settlement in natural surfaces. Settlement of scallop larvae is not random process; an array of species-specific organic (filamentous red algae and hydroids) or inorganic surfaces (gravel, pebbles, mollusk shells) seem to facilitate settlement and provide refuge for settlers.…”