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- Setting preliminary biometric baselines for new target sea cucumbers species of the NE Atlantic and Mediterranean fisheriesPublication . González-Wangüemert, Mercedes; Valente, Sara; Henriques, Filipe; Domínguez-Godino, Jorge A.; Serrao, EsterCommercial interest on sea cucumber species from the NE Atlantic and the Mediterranean is increasing.Holothuria polii, Holothuria tubulosa, Holothuria mammata and Holothuria arguinensis are the new targetspecies. The scarce biological and ecological knowledge on these species along their geographical distri-bution, is a major problem for their fisheries management. To address it, we carried out a morphometricstudy to describe the baseline population size structure, focused on the length–weight relationship andsize–weight distribution.In the NE Atlantic, the largest mean size and heaviest mean weight of H. mammata and H. arguinensiswere found in localities with upwelling, but another factors could be influencing on these results. In theMediterranean, Girona and Mallorca showed the heaviest specimens of H. polii, H. tubulosa and H. mam-mata, and the smallest were registered in Crete and Kusadasi. Significant differences in length and weightbetween populations were found for each species. These results could be linked with local environmentalconditions. Size frequency distribution was multimodal for all species except for H. mammata; the weightfrequency distribution was only unimodal for H. polii and H. mammata.This study provides novel data, helpful for stock and population assessment which could support theimplementation of effective management for the European sea cucumber target species.
- Do hatchery-reared sea urchins pose a threat to genetic diversity in wild populations?Publication . Segovia-Viadero, M.; Serrao, Ester; Canteras-Jordana, J. C.; Gonzalez-Wangueemert, MercedesIn salmonids, the release of hatchery-reared fish has been shown to cause irreversible genetic impacts on wild populations. However, although responsible practices for producing and releasing genetically diverse, hatchery-reared juveniles have been published widely, they are rarely implemented. Here, we investigated genetic differences between wild and early-generation hatchery-reared populations of the purple sea urchin Paracentrotus lividus (a commercially important species in Europe) to assess whether hatcheries were able to maintain natural levels of genetic diversity. To test the hypothesis that hatchery rearing would cause bottleneck effects (that is, a substantial reduction in genetic diversity and differentiation from wild populations), we compared the levels and patterns of genetic variation between two hatcheries and four nearby wild populations, using samples from both Spain and Ireland. We found that hatchery-reared populations were less diverse and had diverged significantly from the wild populations, with a very small effective population size and a high degree of relatedness between individuals. These results raise a number of concerns about the genetic impacts of their release into wild populations, particularly when such a degree of differentiation can occur in a single generation of hatchery rearing. Consequently, we suggest that caution should be taken when using hatchery-reared individuals to augment fisheries, even for marine species with high dispersal capacity, and we provide some recommendations to improve hatchery rearing and release practices. Our results further highlight the need to consider the genetic risks of releasing hatchery-reared juveniles into the wild during the establishment of restocking, stock enhancement and sea ranching programs.
- Genetic differentiation of Diplodus sargus (Pisces: Sparidae) populations in the south-west MediterraneanPublication . González-Wangüemert, Mercedes; Pérez-Ruzafa, Á.; Marcos, C.; García-Charton, J. A.Allozyme analysis of tissue samples of 1249 white sea bream Diplodus sargus from five localities of the south-west Mediterranean revealed a high degree of genetic polymorphism. The observed heterozygosity ranged from 0.4182 (Cape of Palos) to 0.3138 (Tabarca). Several populations were characterized by unique alleles. Examination of the spatial structure was performed using Nei’s distances and F-statistics, and indicated genetic differences between groups. One group, which clustered Tabarca and Guardamar, could be explained by the small geographical distance between them. Mazarrón and Cape of Palos samples showed genetic divergence from other samples (Guardamar, Tabarca and Águilas) and this difference may be as a result of local current systems and larval dispersal.
- Modelling spatial and temporal scales for spill-over and biomass exportation from MPAs and their potential for fisheries enhancementPublication . Pérez-Ruzafa, Ángel; Martín, Ernesto; Marcos, Concepción; Zamarro, José Miguel; Stobart, Ben; Harmelin-Vivien, Mireille; Polti, Sandrine; Planes, Serge; García-Charton, José Antonio; González-Wangüemert, MercedesMarine protected areas (MPAs) are considered as a tool for marine conservation and sustainable fishery resource management. Improvements in fishery yields should take place via the spill-over of individuals from the reserve. In general, it has been demonstrated that MPAs affect the density and biomass of the organisms within them, however, little evidence has been found in order to assess the exportation of individuals across their boundaries. In this study, a simple model involving population growth, harvest, and the diffusion coefficient for individuals was used to explore the effects of protection on populations inside the reserve and the spill-over of individuals to the fished area. The model showed that biological responses inside marine reserves appear to develop quickly, reaching mean levels within a short (1–5 year) time period. Mean population abundance is always higher inside the reserve and highlights the effectiveness of protection, particularly when there is strong fishing pressure outside the reserve. However, reserves smaller than 2000 m radius show significantly lower levels of abundance inside than larger sites. Large MPAs (i.e. about 2000 m in radius) offer nearly the maximum capacity for recovery (close to 100% of the system carrying capacity) and nearly the maximum flux of individuals per unit boundary length. Very large MPAs (i.e. larger than 6000 m in radius) could be a guaranteed means of providing resilience in order to prevent population crises, with the added advantage that the flux of individuals is slightly higher at larger distances from the boundary. However, in practice they provide no further advantage towards increasing the density of individuals or the exportation of biomass, and a network of smaller MPAs could be more beneficial, both from the point of view of conservation and of benefits to fisheries.
- First record of the Atlantic blue crab Callinectes sapidus (Crustacea: Brachyura: Portunidae) in the Segura River mouth (Spain, southwestern Mediterranean Sea)Publication . González-Wangüemert, Mercedes; Pujol, Juan AntonioA single male individual of Callinectes sapidus (Crustacea, Decapoda, Portunidae) was collected on 6 December 2014 in the Segura River mouth in southeastern Spain. Information on collection site, DNA barcoding, and its present distribution and dispersal strategies are provided.
- Environmental variables, habitat discontinuity and life history shaping the genetic structure of Pomatoschistus marmoratusPublication . Gonzalez-Wangueemert, Mercedes; Vergara-Chen, CarlosCoastal lagoons are semi-isolated ecosystems exposed to wide fluctuations of environmental conditions and showing habitat fragmentation. These features may play an important role in separating species into different populations, even at small spatial scales. In this study, we evaluate the concordance between mitochondrial (previous published data) and nuclear data analyzing the genetic variability of Pomatoschistus marmoratus in five localities, inside and outside the Mar Menor coastal lagoon (SE Spain) using eight microsatellites. High genetic diversity and similar levels of allele richness were observed across all loci and localities, although significant genic and genotypic differentiation was found between populations inside and outside the lagoon. In contrast to the FST values obtained from previous mitochondrial DNA analyses (control region), the microsatellite data exhibited significant differentiation among samples inside the Mar Menor and between lagoonal and marine samples. This pattern was corroborated using Cavalli-Sforza genetic distances. The habitat fragmentation inside the coastal lagoon and among lagoon and marine localities could be acting as a barrier to gene flow and contributing to the observed genetic structure. Our results from generalized additive models point a significant link between extreme lagoonal environmental conditions (mainly maximum salinity) and P. marmoratus genetic composition. Thereby, these environmental features could be also acting on genetic structure of coastal lagoon populations of P. marmoratus favoring their genetic divergence. The mating strategy of P. marmoratus could be also influencing our results obtained from mitochondrial and nuclear DNA. Therefore, a special consideration must be done in the selection of the DNA markers depending on the reproductive strategy of the species.
- Improving the fitness of Holothuria arguinensis larvae through different microalgae dietsPublication . Dominguez-Godino, Jorge A.; Gonzalez-Wanguemert, MercedesDevelopment and design of adequate feeding protocols on sea cucumber larvae are necessary for improvements on larvae growth, survival and production of competent juveniles. This work assessed the Holothuria arguinensis larvae growth and survival, fed with three different single microalgae diets of Chaetoceros calcitrans, Isochrysis galbana and Tetraselmis chui, and two microalgae diets based on a combination of C. calcitrans and T. chuii (C:T 1:1) and C. calcitrans, T. chuii and I. galbana (C:T:I 1:1:1) during 2 months. Holothuria arguinensis larvae fed with T:C:I, showed higher survival and larger larval and stomach sizes than the ones fed with the other diets. Comparing the results obtained from the single diets, H. arguinensis larvae fed with I. galbana grew and survived better during the first 5 days. However, higher growth was obtained on the larvae fed with C. calcitrans from day 5 to day 12 since this day, larvae fed with T. chuii showed the largest size. These results could be related to the different microalgae size and morphology, in addition to the nutritional value of the different microalgae used. However, no competent larvae that metamorphosed into doliolaria were obtained during this experiment. The tanks used were transparent, which could be causing light stress to the larvae, since competent larvae were obtained in opaque production tanks in our aquaculture installations during the same time period. The combined diet of C. calcitrans, T. chuii and I. galbana (C:T:I) could improve the growth and larvae competency of H. arguinensis.
- Genetic differentiation in two cryptic species of Ostreidae, Ostrea edulis (Linnaeus, 1758) and Ostreola stentina (Payraudeau, 1826) in Mar Menor Lagoon, southwestern Mediterranean SeaPublication . González-Wangüemert, Mercedes; Pérez-Ruzafa, A.; Rosique, M. J.; Ortiz, A.Ostrea edulis is a target species for aquaculture but its hatchery has suffered as a result of the lack of morphological differentiation between individuals with a low growth and those that reach commercial size. Two sympatric species of oysters, Ostrea edulis and Ostreola stentina, have been reported at the Mar Menor Lagoon, Spain. A third nominal species, Ostreola parenzani, is now considered a synonym of O. stentina. The external morphology of O. edulis and O. stentina is very similar and this prevents their differentiation at the morphological level, except for maximum size. Oysters were collected from 3 locations along the Mar Menor Lagoon and examined for variation at the PGI locus. Principal component analysis of allo-zyme data revealed the existence of two groups, which confirms the presence of two species: Ostrea edulis and Ostreola stentina. The genetic variability of the glucose-6-phosphate isomerase (PGI) locus was also compared in Ostrea edulis and Ostreola stentina from the Mar Menor Lagoon. Ostrea edulis has high levels of homozygosis and shows an important deviation from the Hardy-Weinberg equilibrium. Ostreola stentina shows high heterozygosis and significant differentiation among coastal lagoon samples. The allele frequencies at the PGI locus can be used as a diagnostic character at the species level.
- Effects of fishing protection on the genetic structure of fish populationsPublication . Pérez-Ruzafa, Ángel; González-Wangüemert, Mercedes; Lenfant, Philippe; Marcos, Concepción; García-Charton, José AntonioMarine reserves have been identified as an important tool in the management of fishery resources and their number is increasing rapidly, most of them being on islands. However, knowledge on the real effect of protection from fishing on the genetic structure of populations, the spatial scales involved, or the suitability of islands as reserves in terms of connectivity, is scarce. This paper analyses the effects of fishery protection on the genetic structure of populations of Diplodus sargus, a target species, in protected and non-protected areas of the western Mediterranean. Populations studied showed high genetic variability at spatial scales from 101 to 103 km. Protected areas have significantly higher allelic richness. The lower levels of heterozygosis and higher heterozygote deficit showed by islands compared with coastal areas makes clear the importance of considering the connectivity processes when designing a MPA.
- Identification of weakfish Cynoscion (Gill) in the Bay of Panama with RFLP markersPublication . Vergara-Chen, Carlos; González-Wangüemert, Mercedes; Bermingham, Eldredge; D’Croz, L.A molecular approach, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), was developed to identify the planktonic larvae of Cynoscion species. Species-specific mitochondrial DNA markers were developed using three restriction endonucleases (DdeI, HaeIII and HinfI). These markers permitted the accurate discrimination of the five Cynoscion species in the Bay of Panama.