Metazoan parasites as biological tags for stock discrimination of whitemouth croaker Micropogonias furnieri

Examination of 248 adult specimens of whitemouth croaker Micropogonias furnieri from five localities along the Brazilian coast revealed 8735 parasites belonging to 41 metazoan species. Samples from Ceará to Bahia and Rio de Janeiro to Santa Catarina showed a high level of correct assignation (92 and 87%, respectively) and cross assignation (i.e. almost all specimens misidentified in Ceará were assigned to Bahia and almost all specimens misidentified in Bahia were classified as Ceará), so samples were pooled in the northern and south‐eastern samples, and Rio Grande do Sul was considered a southern area. Eight parasite species were characteristic of the northern localities, five species were found just in the area associated with south‐eastern localities and two species were characteristic of the southern area providing first evidence of stock discreteness. The multivariate discriminant analysis successfully discriminated three groups of localities associated with three stocks of M. furnieri in Brazil: a northern stock associated with Ceará and Bahia, a south‐eastern stock related to Rio de Janeiro and Santa Catarina and a southern stock in the area of Rio Grande do Sul, which could be considered as the northern limit of the stock associated with the Common Fishing Zone of Uruguay and Argentina.     

Local variability in metazoan parasites of the pelagic fish species, Engraulis ringens: implications for fish stock assessment using parasites as biological tags

Parasites have been used successfully as biological tags in population studies, mainly in marine fishes, but also in marine mammals, crustaceans and molluscs. Almost all published information dealing with parasites as biological tags evaluates differences between localities. However, local variability in the component community has not been assessed. In this work, we examined whether local variation of the metazoan parasite fauna of Engraulis ringens, extracted from five independent samples from two nearby localities in northern Chile, can be a factor causing bias in stock identification. Our results show that local variability, as estimated by a single sample, may suffice to represent component community variability with no need for replicated data.     

Metazoan parasites of Sebastes capensis from two localities in northern Chile as tools for stock identification

Examination of 290 red rockfish Sebastes capensis from two fishing grounds in northern Chile (Coquimbo 71°30' W; 30°0' S and Antofagasta 70°40' W; 23°30' S) revealed 8770 metazoan parasites, belonging to 18 taxa: Udonella caligorum (Udonellidae); Interniloculus chilensis , Paramicrocotyle sp. and Neobenedenia melleni (Monogenea); larval Gnathia sp., Cirolana sp. and Rocinela sp. (Isopoda); Helicometrina nimia , Diphtherostomum sp., Lecithochirium sp. and Pseudopecoelus sp. (Digenea); Ascarophis sebastodis , Anisakis sp. and larval Hysterothylacium sp. (Nematoda); Caligus cheilodactylus , Lepeophtheirus chilensis and Trifur tortuosus (Copepoda); larval Corynosoma australe (Acanthocephala). Ten species were found only in Coquimbo and three were found only in Antofagasta, species common to both localities were Pseudopecoelus sp., C. australe , Anisakis sp. and A. sebastodis . Evidence, based on qualitative differences between the parasite faunas of the red rockfish, suggests the existence of two discrete stocks.     

Metazoan parasites of Macruronus magellanicus from southern Chile as biological tags

Examination of 450 specimens of Macruronus magellanicus from two fishing grounds in southern Chile (Talcahuano: 36°40'S, Punta Arenas: 54° S) revealed 24 205 metazoan parasites, belonging to 15 taxa with low specificity: Chondracanthus australis and Neobrachiella sp. (Copepoda); Elytrophalloides oatesi, Gonocerca phycidis, Derogenes varicus and Brachyphallus parvus , (Digenea); Hepatoxylon trichiuri, Scolex pleuronectis, Clestobothrium crassiceps, Grillotia dollfusi , Pseudophyllidea gen. sp. (Cestoda); Anisakidae, Cucullanus sp. (Nematoda), Corynosoma australe and Acanthocephala gen. sp. (Acanthocephala). The list includes parasites that are common to other merluccids from the zone. The parasitological evidence does not suggest the existence of two discrete stocks, but the existence of a migratory process from south to north.     

Metazoan parasites as biological indicators of population structure of Halobatrachus didactylus on the Portuguese coast

A total of 366 Halobatrachus didactylus (Bloch & Schneider 1801) individuals were obtained between September and November 2000 from commercial fishing vessels at eight localities along the Portuguese coast and analysed for metazoan parasite infections. Three species of parasites were found: Hysterothylacium aduncum Rudolphi 1802; Progrillotia dasyatidis Beveridge et al. 2004, which constitutes a new host record for the Lusitanian toadfish; and Nerocila orbignyi Guérin‐Méneville 1829. Prevalence and mean abundance were determined for the total fish population in each sample. Significant differences in the number of parasitized fish among the samples analysed indicate differences in the H. didactylus populations along the Portuguese coast. The cluster analysis performed to prevalence data pointed out two major clusters: one composed of mainly estuarine samples and one that grouped samples from coastal areas; this is in agreement with the results obtained by morphological and genetic analysis performed for the same samples.     

Metazoan parasites of the thumb grenadier Nezumia pulchella, from the south-eastern Pacific, off Chile, and their use for discrimination of host populations

The parasite communities of Nezumia pulchella across its geographical range in the south-eastern Pacific were described, from 217 fish captured from four localities in northern and central Chile (24° S to 33° S). Five ectoparasites and 13 endoparasites were recorded and the highest prevalence and intensity of infection was found for the copepods Jusheyhoea macrura and Clavella sp. 1, for the monogenean Diclidophora sp. and for the larval acanthocephalan Corynosoma australe . Parasite species richness decreased with latitude. Multivariate discriminant analysis and correspondence analysis supported the use of parasites of N. pulchella to discriminate populations of this host, suggesting the existence of three well-defined host populations in the geographical range examined. Jusheyhoea macrura , C. australe , Lophoura sp., Diclidophora sp., Capillaria sp. and Proleptus sp. were the most important species for discriminant analysis.     

Movement and stock structure of narrow-barred Spanish mackerel as indicated by parasites

Data from permanent parasites (juvenile trypanorhynchs and anisakids) indicated that Spanish mackerel Scomberomorus commerson from four sites on the west coast of Australia, Abrolhos. Shark Bay, Exmouth and Onslow, intermingled and were probably all drawn from the same stock. Fish from Broome, Kupang (Indonesia), Groote Eylandt-Torres Strait and the east coast of Australia had distinct faunas of permanent parasites and probably each belonged to a different stock. There was evidence of movement of fish between Broome and the west coast. Abundances of temporary parasites (gill copepods and monogeneans) suggested that males and females on the west coast migrated separately because in several cases the parasite fauna of one sex was more similar to that offish in an adjacent area than to the opposite sex in the same area.     

The stock structure and migrations of plaice populations on the west coast of England and Wales

Plaice Pleuronectes platessa populations on the west coast of England and Wales are currently managed as two stocks: in ICES Division VIIa (Irish Sea, Cardigan Bay and St George's Channel), and ICES Divisions VIIf&g (Bristol Channel and Celtic Sea). A total of 13,784 plaice were fitted with Petersen tags and released in these areas during 1979–1980 and 1993–1996. Analysis of the 2788 recaptures received by June 2000 confirmed known spawning and feeding grounds in the region. It showed also that plaice >25 cm L _T tended to undertake extensive spatial movements. At this size, female plaice were likely to be mature or maturing for the first time, whilst males were probably mature. Tag recaptures indicated resident sub-stocks of plaice in the north-east Irish Sea, the south-east Irish Sea, Cardigan Bay and Bristol Channel, a contingent of plaice in all areas that undertook permanent dispersal to other areas, and a contingent which originated in the south-east Irish Sea and migrated to spawn in the Bristol Channel. Plaice originating in the Bristol Channel rarely moved north into ICES Vila. A general hypothesis of plaice population structure in the region is presented and discussed in relation to stock assessment.     

Morphological variability of the shape of striped red mullet Mullus surmuletus in relation to stock discrimination between the Bay of Biscay and the eastern English Channel

Truss analysis and length measurements were made on 168 striped red mullet Mullus surmuletus. Multivariate statistical analyses with principal component analysis and partial redundancy analysis (pRDA) were used on these measurements to evaluate the influence of maturity, sex and geographical area distribution on body shape. Truss measurements were important to quantify and discriminate changing body shape, presumably due to changing environmental conditions. Sexual dimorphism was not observed and juveniles could be distinguished from adults based on their body shape. More importantly, M. surmuletus occurring in different geographical areas could be differentiated using this method. Based on pRDA, a significant difference of head morphological dimensions was observed between populations occurring in the eastern English Channel and those occurring in the Bay of Biscay, suggesting that fish from these areas could represent two subpopulations.     

Using new tools to identify eggs of Engraulis anchoita (Clupeiformes,Engraulidae)

Efficiency of the identification of eggs of Engraulis anchoita can be greatly improved by a method developed from egg measurements, using photography and the ImageJ programme, analysed by discriminant analysis using R software.     

Stock structure of blue threadfin Eleutheronema tetradactylum on the Queensland east coast, as determined by parasites and conventional tagging

Blue threadfin Eleutheronema tetradactylum (Polynemidae) were examined from four areas (Princess Charlotte Bay, Trinity Inlet, Halifax Bay and Upstart Bay) in eastern Queensland covering a distance of c . 950 km of coastline. Parasites were used as biological markers to infer stock structure of E. tetradactylum . Parasites designated as 'temporary' biological markers were the copepod Thysanote eleutheronemi , the acanthocephalan Neoechinorhynchus topseyi , the nematode Philometra rajani and hemiurid trematodes. The larval nematodes Anisakis sp. Type 1 and Terranova sp. Type 2; and the larval cestodes Pterobothrium pearsoni and Callitetrarhynchus gracilis were considered 'permanent' biological markers. Both univariate and multivariate analyses demonstrated that there was little difference in temporary parasite abundance between the four areas. In contrast, the same analyses revealed that most areas had two or more significant differences in permanent parasite abundance, with the exception of Halifax Bay and Upstart Bay, which were significantly different only in the multivariate analysis. Biological markers predicted that Princess Charlotte Bay and Trinity Inlet consisted of distinct populations, whereas Halifax Bay and Upstart Bay were not clearly differentiated. Tag recapture data supported this hypothesis; the majority of recaptures were within 100 km of the initial tagging location. Geographical movement of E. tetradactylum may be limited due to their biology and ecology, as well as the distances and oceanographic boundaries that separate habitats. Contrary to current management definitions, the stock structure of E. tetradactylum on the east coast of Queensland appears to be geographically differentiated at a small spatial scale.     

Stock differentiation of the greater lizardfish Saurida tumbil (Teleostei: Synodontidae) collected along the western coast of the Arabian Gulf and Sea of Oman using meristic characters

Meristic variation among stocks of greater lizardfish Saurida tumbil through the western coasts of the Arabian Gulf and Sea of Oman was examined using meristic characters. Statistical analysis of meristic traits proposed that there is constrained migration of populations of greater lizardfish along the western coast of the Arabian Gulf and Sea of Oman. Overlapping of the two samples from the northern part of the Arabian Gulf (Iraq-Kuwait waters), three samples from the middle region of the Arabian Gulf (Bahrain-Qatar-Saudi Arabia) and two samples from the southern part of the Arabian Gulf/Sea of Oman (United Arab Emirates–Sultanate of Oman) suggested that there are three self-recruiting populations in the studied area. Inspection of the role of each meristic trait variable to Canonical discriminant analysis showed that changes among samples appeared to be linked with the pattern of distribution of water temperature and configuration of current in both the Arabian Gulf and Sea of Oman areas.     

Assessing seasonal changes in stock composition of Atlantic salmon catches in the Baltic Sea with genetic stock identification

The feasibility of using genetic stock identification to analyse seasonal changes in stock compositions of Atlantic salmon catches in the Baltic Sea was examined. The analysis employed seven variable allozyme loci from most of the potentially contributing stocks (16) from Finland and Sweden. Catch samples were collected from Finnish salmon fisheries in the eastern Bothnian Sea during the 1992 fishing season. Simulation studies were used to evaluate the feasibility of identifying Baltic salmon stocks with allozyme data. Special attention was paid to analysing the wild production of salmon stocks. Clear seasonal differences in stock composition were found. The estimates were compared with smolt production and Carlin-tag data. The proportions of the Neva and Oulujoki river stocks could be estimated as individual stocks, whereas the contributions of the remaining stocks were estimated as four composite stock groups. One of the groups consisted of wild stocks from the rivers Kalixälven and Simojoki. Identification of this group, which could be used as an index of wild production in the catches, requires catch sample sizes >300 salmon if <15% error is required.     

DNA fingerprinting and new tools for fine-scale discrimination of Arabidopsis thaliana accessions

One of the main strengths of Arabidopsis thaliana as a model species is the impressive number of public resources available to the scientific community. Exploring species genetic diversity--and therefore adaptation--relies on collections of individuals from natural populations taken from diverse environments. Nevertheless, due to a few mislabeling events or genotype mixtures, some variants available in stock centers have been misidentified, causing inconsistencies and limiting the potential of genetic analyses. To improve the identification of natural accessions, we genotyped 1311 seed stocks from our Versailles Arabidopsis Stock Center and from other collections to determine their molecular profiles at 341 single nucleotide polymorphism markers. These profiles were used to compare genotypes at both the intra- and inter-accession levels. We confirmed previously described inconsistencies and revealed new ones, and suggest likely identities for accessions whose lineage had been lost. We also developed two new tools: a minimal fingerprint computation to quickly verify the identity of an accession, and an optimized marker set to assist in the identification of unknown or mixed accessions. These tools are available on a dedicated web interface called ANATool (https://www.versailles.inra.fr/ijpb/crb/anatool) that provides a simple and efficient means to verify or determine the identity of A. thaliana accessions in any laboratory, without the need for any specific or expensive technology.     

Unravelling the stock structure of the Persian brown trout by otolith and scale shape

The simultaneous use of the scale and otolith morphometry was assessed as a potential tool for the identification of Persian brown trout Salmo trutta stocks of the Lar Lake and five rivers from Lar Basin, Iran. Fourier coefficients (FC) and circularity, rectangularity, roundness, ellipticity and form factor shape indices (SI) were calculated for otolith and scale. Several SIs were significantly different among sites for both structures. Permutational multivariate analysis of variance revealed significant differences between several pairwise comparisons for otolith and scale (FCs and indices separately). Discriminant analysis showed otolith FCs (cross-classification rates: 25–86%) and SI (20–45%) appear to be a relatively acceptable tool to discriminate between several locations. Comparatively, the scale morphometry showed lower discriminatory power (FC = 3–65%; SI = 15–34%), with the exception of SI for Elarm River (60%), Kamardasht River (56%) and Lar Lake (75%). Cross-classification rates improved up to 100% when discriminate analysis incorporating all variables for otolith and scale was performed. The results showed a potential segregation between some water bodies, suggesting that the otolith and scale morphometry could be a useful tool to delimit S. trutta populations in relatively close freshwater environments.     

Stock discrimination and movements of narrow‐barred Spanish mackerel across northern Australia as indicated by parasites

The parasite fauna of Spanish mackerel Scomberomorus commerson from 10 sites across northern Australia and one site in Indonesia, was examined to evaluate the degree of movement and subsequent stock structure of the fish. Kupang fish (Indonesia) had very few Terranova spp., Grillotia branchi , Otobothrium cysticum or Pterobothrium sp. compared to Australian fish, indicating that no Australian fish enter the Kupang fishery. Univariate and discriminant function analysis of four 'temporary' parasite species, the copepod Pseudocycnoides armatus and the monogeneans Gotocotyla bivaginalis , Pricea multae and Pseudothoracocotyla ovalis , demonstrated little similarity between areas of northern Australia, indicating minimal short‐term exchange between neighbouring groups of S. commerson . Analyses of five 'permanent' parasite species, the larval helminths G. branchi , O. cysticum , Pterobothrium sp., Callitetrarhynchus gracilis and Paranybelinia balli , also revealed large differences between areas thus indicating long‐term separation. There are at least six parasitological stocks across northern Australia: Fog Bay/Bathurst Island, Cape Wessel, Groote/Sir Edward Pellew, Mornington Island, Weipa, and the Torres Strait. The occurrence of a few irregular fish in the samples suggested that up to 5% of fish moved between stocks during their lifetime. The similarity of within‐school variability to that between schools showed that the fish do not form long‐term school associations.     

The use of otolith shape to determine stock structure of <Emphasis Type="Italic">Engraulis encrasicolus</Emphasis> along the Tunisian coast

Engraulis encrasicolus is of great economic importance in the Mediterranean. However, little is known about its stock structure. Otolith shape analysis has been successfully used for fish stock identification. In this study, the stock structure of anchovy caught off the open sea and the coastal area of the Gulf of Tunis, lagoon of Bizerte and Lake of Ichkeul were investigated using otolith shape. Otolith shape was determined by Fourier analysis and then compared among specimens sampled from different areas with forward stepwise canonical discriminant analysis. Significant differences in otolith shape between the open sea and inshore anchovy groups were detected. Otolith shape of anchovy collected in the Lake of Ichkeul was distinct from the other groups. This finding suggests a clear discreteness of the open sea and the continental groups. The data highlighted the potential for using otolith shape analysis for anchovy stock identification, as well as the role of oceanographic features in determining stock separation. These findings will have major implications for anchovy fisheries management in Tunisia. By using a precautionary approach and considering the three areas as separate stocks, fisheries management strategies should be adjusted to achieve optimum sustainable production from each stock and to avoid decreases in genetic variety.     

Testing the abundant‐centre hypothesis using intertidal porcelain crabs along the Chilean coast: linking abundance and life‐history variation

Aim The abundant‐centre hypothesis (ACH) is based on the assumption that physiological constraints limit populations at the edges of their distributional range, yet the geographical variation of physiological performance or life‐history traits has rarely been examined. Here we examine the applicability of the ACH in a marine system by testing whether physiological predictions are reflected in large‐scale variations of life‐history traits. Location The Chilean coast (18°–42° S), encompassing more than 2500 km along the Pacific coast of South America. Methods Five porcelain crab species (Petrolisthes granulosus, Petrolisthes laevigatus, Petrolisthes tuberculatus, Petrolisthes violaceus and Allopetrolisthes angulosus) were sampled on intertidal boulder beaches at 13 sampling sites. For each species and site we evaluated: (1) relative abundance (density), (2) maximum size, (3) size at maturity, (4) sex ratio, (5) proportion of ovigerous females, and (6) presence of recruits. The shape of the spatial distribution of each trait was evaluated statistically against the prediction of four hypothetical models (normal, ramped‐south, ramped‐north and abundant‐edge). Results The relative abundance and life‐history traits showed different spatial patterns among species. Relative abundance (across sites) was fitted by a normal model in only two species. No model fitted the spatial variation in body size and size at first maturity, which showed a slight but monotonic poleward increase in all species. Sex ratio showed a prominent hump‐shaped pattern, with females prevailing in the centre of the ranges and males dominating towards the range boundaries; this pattern was statistically significant in three of the five studied species. The proportion of ovigerous females showed no clear latitudinal trends, and mature individuals were observed across most of the geographical range of the species. However, recruits tended to be absent towards the southern (poleward) boundaries of the distribution. Main conclusions The ACH does not apply to all species equally. The link between abundance and life‐history traits is complex and variable among the porcelain crab species studied. Overall, the observed patterns were consistent with the idea that equatorward boundaries might be controlled by physiological restrictions mainly affecting adult survival, whereas poleward boundaries might be shaped by limitations in reproductive output and larval survival. Our results underline the importance of incorporating ecological, physiological and life‐history studies in future tests of the ACH.