The great melting pot. Common sole population connectivity assessed by otolith and water fingerprints

Quantifying the scale and importance of individual dispersion between populations and life stages is a key challenge in marine ecology. The common sole (Solea solea), an important commercial flatfish in the North Sea, Atlantic Ocean and the Mediterranean Sea, has a marine pelagic larval stage, a benthic juvenile stage in coastal nurseries (lagoons, estuaries or shallow marine areas) and a benthic adult stage in deeper marine waters on the continental shelf. To date, the ecological connectivity among these life stages has been little assessed in the Mediterranean. Here, such an assessment is provided for the first time for the Gulf of Lions, NW Mediterranean, based on a dataset on otolith microchemistry and stable isotopic composition as indicators of the water masses inhabited by individual fish. Specifically, otolith Ba/Ca and Sr/Ca profiles, and delta C-13 and delta O-18 values of adults collected in four areas of the Gulf of Lions were compared with those of young-of-the-year collected in different coastal nurseries. Results showed that a high proportion of adults (>46%) were influenced by river inputs during their larval stage. Furthermore Sr/Ca ratios and the otolith length at one year of age revealed that most adults (similar to 70%) spent their juvenile stage in nurseries with high salinity, whereas the remainder used brackish environments. In total, data were consistent with the use of six nursery types, three with high salinity (marine areas and two types of highly saline lagoons) and three brackish (coastal areas near river mouths, and two types of brackish environments), all of which contributed to the replenishment of adult populations. These finding implicated panmixia in sole population in the Gulf of Lions and claimed for a habitat integrated management of fisherie

The power of integrating genetic and otolith analytical approaches into the management of exploited marine fishes

Marine exploited populations exhibit various degrees of discreteness, ranging from historical evolutionary to contemporary ecological levels of differentiation. An integrated approach combining complementary population discrimination tools such as otolith microchemistry and genetics may capitalize on these different time scales to improve the discrimination and traceability power in management applications. Additionally, novel statistical and technological improvements have enabled the joint extraction of demographic, life-history and genetic information from archived otolith collections, to unveil the evolutionary consequences of anthropogenic pressure in wild fish populations. Here, I overview the most recent integrated results obtained from genetic markers (microsatellites and SNPs) and otoliths (growth-maturity, microchemistry and shape data) on adult sole (Solea solea) populations in the North-East Atlantic Ocean. While genetic markers provide a clear regional differentiation and local adaptation pattern, otoliths data often provide an improved small scale geographical resolution. At the temporal scale, combining molecular and otolith back-calculation data enables a powerfull assessment of changes in population size/demography, while tracing back the genetic basis of life-history trait evolution under heavy anthropogenic pressure. Our results highlight the power of a multi-marker approach depending on the required spatial resolution scale and emphasize the relevance of integrated phenotypic-genetic temporal analyses to unveil human induced selection factors in future management scenarios. Monitoring efficiently the resilience of marine harvested populations hence requires interdisciplinarity in research priorities, covering both the evolutionary and ecological components of population connectivity and demography

The power of integrating genetic and otolith analytical approaches into the spatial management of exploited marine fishes

Marine exploited populations exhibit various degrees of discreteness, ranging from historical evolutionary to contemporary ecological levels of differentiation. An integrated approach combining complementary population discrimination tools such as otolith microchemistry and genetics may capitalize on these different time scales to improve the discrimination and traceability power in management applications. Here, I discuss the most recent integrated results obtained from genetic markers (microsatellites and SNPs) and otoliths (microchemistry and shape data) on juvenile/adult sole (Solea solea) populations in the North-East Atlantic Ocean. While genetic markers provide a clear regional differentiation and local adaptation pattern, otoliths data often provide an improved small scale geographical resolution. Our results highlight the power of a multi-marker approach depending on the required spatial resolution scale in future management scenarios. Monitoring efficiently the resilience of marine harvested populations hence requires interdisciplinarity in research priorities, covering both the evolutionary and ecological components of population connectivity. Such information is pivotal to reliably develop, validate and later apply integrated traceability tools for fisheries enforcement

Data from: Temporal genetic stability and high effective population size despite fisheries-induced life-history trait evolution in the North Sea sole.

Heavy fishing and other anthropogenic influences can have profound impact on a species’ resilience to harvesting. Besides the decrease of the census and effective population size, strong declines in mature adults and recruiting individuals may lead to almost irreversible genetic changes in life-history traits. Here, we investigated the evolution of genetic diversity and effective population size in the heavily exploited sole (Solea solea), through the analysis of historical DNA from a collection of 1379 sole (Solea solea) otoliths dating back from 1957. Despite documented shifts in life-history traits, neutral genetic diversity inferred from 11 microsatellite markers showed a remarkable stability over a period of 50 years of heavy fishing. Using simulations and corrections for fisheries induced demographic variation, both point and temporal estimates of effective population size (Ne) were always higher than 1000, suggesting that despite the severe census size decrease over a 50 year period of harvesting, genetic drift is probably not strong enough to significantly decrease the neutral diversity of this species in the North Sea. However the ratio of effective population size to the census size (Ne/Nc) was very small (10-5), suggesting that overall only few adults contribute to the next generation. The high Ne level together with the low Ne/Nc ratio is most likely caused by a combination of an equalized reproductive output of younger cohorts, a decrease in generation time and a large variance in reproductive success typical for marine species. Because strong evolutionary changes in age and size at first maturation have been observed for sole, changes in adaptive genetic variation should be further monitored to detect the evolutionary consequences of human-induced selection

OtolithGenotypes_byCohorts_11loci

Genepop input file. Otolith genotypes (11 loci),grouped by cohort (year-class). Pops are cohorts

OtolithGenotypes_bySamplingyear_11loci

Genepop input: Otolith genotypes (11 loci) grouped by sampling year:1950s (‘NS50’; sampling years 1957-1959), 1960s (‘NS60’; sampling years 1966-1967),1970s (‘NS70’, sampling years 1971-1974), 1980s (NS80, sampling years 1984-1985-1987) and 1995 (NS95) (For details on age composition of the samples, see Supporting Information Table S2). In addition, contemporary samples were collected in 2007 during research surveys off the Thames (THA07), on the Norfolk Banks (NOR07) and off the Belgian Coast (BEL07