Estuary Population Research Articles

Assignment of Acanthopagrus populations in the Persian Gulf drainage system of Iran to Acanthopagrus arabicus Iwatsuki, 2013 (Perciformes: Sparidae)

The distribution of yellowfin seabream populations in estuaries and inland rivers in coastal area of the Persian Gulf and Strait of Hormuz is presented. Based on morphological and mersitic characteristics and also color pattern, these populations are assigned to the recently described sparid fish, Acanthopagrus arabicus Iwatsuki, 2013 which is distinguished by pelvic and anal fins vivid or strong yellow; black streaks proximally on inter-radial membranes between yellow anal-fin rays absent; lower caudal-fin lobe yellow; clear black blotches usually absent just beneath inter-radial membranes between dorsal-fin rays but upper dorsal-fin membrane often with darker margin; weak diffuse dark blotch at origin of lateral line, usually covering first pored lateral-line scale, continuing as a dense dark shading over upper part of posterior opercle.

Introduced Pacific oysters Crassostrea gigas in South Africa: demographic change, genetic diversity and body condition

Successful aquaculture species are often chosen for their fast growth rates and fecundity, which are also characteristics of invasive species. The Pacific oyster Crassostrea gigas, which constitutes 80% of global oyster trade, has been confirmed as invasive in 17 of the 66 countries where it is cultured. The single study of its status in South Africa reported populations in six South Coast estuaries in 2001, dropping to three sites in 2003. We resurveyed these estuaries, visited others in the Eastern and Western Cape provinces, and sampled oyster tissue for molecular analyses of population structure. Pacific oysters have disappeared from Knysna and, following our collections, possibly also from the GouKou Estuary. Between 2003 and 2012, the Breede Estuary population decreased by 87%, from an estimated 184 206 to 23 760 individuals. Within this estuary, oysters 12 km upriver had denser shells and higher body condition indices than did those within 1.4 km of the river mouth, presumably reflecting higher availability of suspended organic matter. However, low salinity over most of the species’ range in the estuary probably inhibits recruitment. New populations of Pacific oysters in the Swartkops and Kaaimans estuaries urgently require monitoring and eradication. Haplotype (h) and nucleotide (π) diversities across all oyster populations sampled (h = 0.2300 [SD 0.0595], π = 0.0006 [SD 0.0007]) were lower than those of co-occurring indigenous Cape rock oysters Striostrea margaritacea from the GouKou and Breede estuaries (h = 0.9076 [SD 0.0386], π = 0.00589 [SD 0.00347]). Pacific oysters either have been introduced to South African estuaries infrequently, or have experienced genetic bottlenecks following river floods or human exploitation, or both. Populations growing outside culture infrastructure are restricted to estuaries in the Eastern and Western Cape provinces, with no evidence of occurrence in fully marine shelf environments. Given the species’ considerable socio-economic importance, estuarine and coastal surveillance coupled with aquaculture zoning are required to integrate biodiversity and food security considerations.

The past and present of an estuarine-resident fish, the "four-eyed fish" Anableps anableps (Cyprinodontiformes, Anablepidae), revealed by mtDNA sequences.

Historical events, such as changes in sea level during the Pleistocene glacial cycles, had a strong impact on coastal habitats, limiting connectivity and promoting the genetic divergence of various species. In this study, we evaluated the influence of climate oscillations and the possibility of estuary function as a barrier to gene flow among populations of the four-eyed fish, Anableps anableps. This species is fully estuarine-resident, has internal fertilization, is viviparous and does not migrate across long distances. These features make the four-eyed fish an excellent model for the study of evolutionary processes related to genetic differentiation of species and populations in estuaries. The evolutionary history of A. anableps was inferred from phylogeographic and population analyses using sequences of the mitochondrial DNA Control Region of 13 populations distributed in the Amazon and Northeast Coast of Brazil from Calcoene (Amapa) to Parnaiba (Piaui). The 83 retrieved haplotypes show a pattern of four distinct mitochondrial lineages, with up to 3.4% nucleotide divergence among them. The evolutionary reconstruction suggests that these lineages diverged recently in the late Pleistocene/early Holocene after the Atlantic Ocean reaching current levels. Analysis of variability, neutrality and the genetic expansion pattern revealed that the lineages have distinct characteristics, which were shaped by the different geomorphological features of coastal regions combined with sea level oscillations over a very long period of time. Only few neighboring populations show a discreet gene flow. This study may also be helpful for designing new experiments to better understand the geomorphological evolutionary history of the estuaries of the Amazon and the Northeast Coast of Brazil using estuarine-resident species as a model.

Microsatellite Genotypes Reveal Some Long-Distance Gene Flow inPerkinsus marinus, a Major Pathogen of the Eastern Oyster,Crassostrea virginica(Gmelin)

ABSTRACT As the agent of Dermo disease, Perkinsus marinus causes significant mortality and reduced fecundity its eastern oyster host, Crassostrea virginica. Passive dispersal of P. marinus between hosts subjects parasite movements to control by water currents in estuarine systems, potentially limiting connectivity among parasite populations in different estuaries. Given recent evidence for sexual reproduction in P. marinus, estimates of gene flow among locations may provide insights into this parasite's epidemiology. In this study, 1,082 wild oysters were collected from 2002 to 2008 at 15 geographical locations encompassing 4,800 km of the Gulf of Mexico and Atlantic coasts of the United States. Of these, 742 oysters (68.9% prevalence) were determined to be infected by P. marinus. Among infected oysters, 374 were determined to be infected by a single parasite genotype based on amplification of seven microsatellite loci, and therefore were amenable to analysis. Allele frequencies differed significantly amo...

Evaluating cumulative effects of anthropogenic inputs in Prince Edward Island estuaries using the mummichog (Fundulus heteroclitus)

Estuarine eutrophication as a result of agricultural land use, including the use of chemical fertilizers, is increasing worldwide. Prince Edward Island (PEI), Canada has very high agricultural intensity by international standards with approximately 44% of the land area under production, and some watersheds in excess of 75% agricultural land-use. The type of agriculture is also intensive with primarily row crops that have high chemical fertilizer and pesticide usage. In light of these stressors, the hypothesis of this study was that mummichog (Fundulus heteroclitus) population parameters would change with point and nonpoint source pollution, and that multivariate statistics could be used to draw associations with specific stressors. Fish were sampled on a monthly basis from May through August at 7 estuaries spanning a range of land use, nutrient, and contaminant loadings. A suite of environmental variables were simplified into 3 principal components: PC1 representing agricultural land use, N loading, and plant habitat, PC2 being dominated by sediment sand and silt distribution, and PC3 largely reflecting P loading and sediment organic matter. There were significant differences in abundance of both adult and young-of-the-year mummichog, and these changes associated most strongly with PC1, the largely N-driven agricultural influences. In contrast, somatic variables such as liver and gonad size did not show strong association with the environmental quality principal component scores. The sand and silt PC2 appeared to have the opposite association with the biological data, with siltier environments correlating to older, larger, less dense populations of mummichog. Although pesticide residues were detected in estuarine sediment, there was no clear relationship between these and watershed agricultural intensity or biochemical indicators. There was, however, a strong relationship between agricultural environmental variables (PC1) and in vitro steroid production that is suggestive of a potential chemical effect. Eutrophication appeared to be a primary stressor affecting mummichog populations, as nutrient enrichment was associated with changes in habitat variables and these in turn were associated with high mummichog density. Thus, mummichog population demographics appear to have use as an indicator of adverse or worsening conditions in estuaries. We concluded that, based on the subset of environmental factors evaluated, the nonpoint-source inputs of sediments and nutrients exerted the greatest influence on mummichog populations in PEI estuaries.

Landmark-based morphometric and meristic variations of Glossogobius giuris in three stocks

Landmark-based morphometric and meristic analysis of pond, haor and estuary populations of Glossogobius giuris (Hamilton,1822) (Perciformes:Gobiidae) were done to find out variations among the three stocks. Samples were collected from three different regions such as pond of Mymensingh, haor of Kishoreganj and estuary of Barisal. Significant differences (*P<0.01) were observed in 13 general morphometric and 23 size adjusted landmark-based morphometric measurements among three stocks. Among the 11 meristic counts the first dorsal fin rays (D1FR), transverse scale above lateral line (TSALL), branchiostegal rays and number of vertebrae were same among fishes of these stocks. In case of pectoral fin rays (PcFR) and transverse scale on lateral line (TSOLL) the haor stock was significantly different from other two stocks. In discriminant space, pond stock was isolated from other two stocks. On the other hand, haor and estuary stocks showed very close relationship. A dendrogram based on the hierarchical cluster analysis using size adjusted general morphometric and landmark measurements formed two main clusterspond stock in one cluster and other two stocks (haor and estuary) remained in another cluster. It indicates that pond stock was separated. The second cluster explained that haor and estuary stocks had very close relationship.DOI: http://dx.doi.org/10.3329/jbau.v10i2.14931 J. Bangladesh Agril. Univ. 10(2): 375-384, 2012

Ecosystem effects of shell aggregations and cycling in coastal waters: an example of Chesapeake Bay oyster reefs

Disease, overharvesting, and pollution have impaired the role of bivalves on coastal ecosystems, some to the point of functional extinction. An underappreciated function of many bivalves in these systems is shell formation. The ecological significance of bivalve shell has been recognized; geochemical effects are now more clearly being understood. A positive feedback exists between shell aggregations and healthy bivalve populations in temperate estuaries, thus linking population dynamics to shell budgets and alkalinity cycling. On oyster reefs a balanced shell budget requires healthy long‐lived bivalves to maximize shell input per mortality event thereby countering shell loss. Active and dense populations of filter‐feeding bivalves couple production of organic‐rich waste with precipitation of calcium carbonate minerals, creating conditions favorable for alkalinity regeneration. Although the dynamics of these processes are not well described, the balance between shell burial and metabolic acid production seems the key to the extent of alkalinity production vs. carbon burial as shell. We present an estimated alkalinity budget that highlights the significant role oyster reefs once played in the Chesapeake Bay inorganic‐carbon cycle. Sustainable coastal and estuarine bivalve populations require a comprehensive understanding of shell budgets and feedbacks among population dynamics, agents of shell destruction, and anthropogenic impacts on coastal carbonate chemistry.

Early stages of a New Zealand invasion by Charybdis japonica (A. Milne-Edwards, 1861) (Brachyura: Portunidae) from Asia: population demography

Charybdis japonica (A. Milne-Edwards, 1861) is an Asian swimming crab from the northern hemisphere whose native range includes China, Japan, Russia, and Malaysia but has recently been introduced to the eastern coast of northern New Zealand. We have undertaken the first study of its population dynamics and reproductive biology in the southern hemisphere during the early stages of its invasion and colonization. Trappings indicate that the Weiti Estuary population (northeastern New Zealand) represents an established population due to the presence of ovigerous females and size distributions demonstrating continued recruitment. Ovigerous females (43.7-79 mm carapace width) hatch at least one brood of up to 415 000 eggs between the austral spring and autumn (November to April) with a peak in summer. Crabs that hatch early in the reproductive season (November, December) attain recruitment size in the following autumn and settle into estuaries. Individuals hatched later in the reproductive season continue to recruit into the population during the winter and early spring. In New Zealand, C. japonica seems to have indeterminate growth as evident by multiple post-maturity instars. When comparing native and introduced populations, it appears that C. japonica does not gain any reproductive advantage in its new environment, e.g., larger brood sizes, increased number of broods, smaller size at maturity. In fact, in Russia, C. japonica females exhibit larger average brood size (1.3×), larger overall female size, and increased fecundity with female size when compared with New Zealand populations. Charybdis japonica has life history characteristics that positively influence invasion success, i.e., early maturation, relatively long life at large body sizes, high fecundity, and long spawning seasons. As New Zealand offers further habitats within its environmental envelope, C. japonica has the potential to be a formidable invader within New Zealand and provide a stepping-stone to other temperate environments via transfer in ship ballast water.

ASPECTOS ECOLÓGICOS Y DISTRIBUCION GEOGRÁFICA DE CARRANGENOPHYTAS

The carragenophytas species are defined as macro-algae, members of the Phylum Rodophyta, Rodophyceae Class, Florideophycidae Subclass, Gigartinales Order. The most important commercial species at the international level are the Betaphycus, Eucheuma and Kappaphycus genera and at the national level the species belonging to the Gigartina, Mazzaella and Sarcothalia genera. Because of its commercial importance, the Gigartina genus has been the object of investigations such as: Ecology of populations in estuaries and open coast in the North-East Atlantic species; it has been studied by Mathieson and Tveter (1976) in relation with its carragenine quantity and quality. Studies about the response to photoperiods (Guiry, 1984; Guiry et al., 1984) have identified reproductive windows suggesting that the explanations for vegetative multiplication are more exclusive each time, different from gametangial or tetra-sporangial production in populations of high latitudes from a generalized European species. Genetic determination of ramification patterns and tolerance limits to temperature has been established for several species (Guiry et al., 1987; Buschmann, 2001). Species cultivation viability in artificial substrates has been evaluated by Mumford y Waaland (1980), and it showed commercial potential. This genus has distribution worldwide in warm and cold seas. However, very few species happen in subtropical regions. The particularly rich species biodiversity centers are California, Japan, New Zealand, Chile y South Africa (Guiry, M.D & Guiry, G.M. 2011).

Lipids and fatty acids from Ulva intestinalis from estuaries of the Caspian basin (Elton Region)

The fatty-acid composition of total lipids from eurybiotic species of green alga Ulva intestinalis from saltwater and estuaries of the Caspian arid zone basin (Elton Region) was studied. It was shown that the relative content of trienoic acids increased and the relative content of long-chain acids decreased as the salinity of the water increased. A feature of the phospholipid composition of U. intestinalis estuary populations was the presence of phosphatidylcholine in plants growing in water with salinity 10.0–11.6 g/L and its absence in algae at higher salinities (28.5–31.2 g/L).

Two social communities in the Pearl River Estuary population of Indo-Pacific humpback dolphins (Sousa chinensis)

The way human activities impact animal populations can depend on social structure, which is important to understand in social species such as cetaceans. We investigated association patterns in Indo-Pacific humpback dolphins ( Sousa chinensis (Osbeck, 1765)) inhabiting the Pearl River Estuary near Lantau Island, Hong Kong, using a 10-year data set for 88 individuals. Our analyses revealed two social communities. Each had its own region of core use, to the north and to the west of the island, but their overall ranges partially overlapped northwest of Lantau. The northern community had a fission–fusion structure characterized by short-term associations, while the western community had more long-term associations. Mixed-community groups included calves more often than exclusive groups, so between-community associations may arise from common habitat usage, by females especially, in the overlap area. Recent range extensions by the northern community into the west are likely a response to habitat destruction north of Lantau. This suggests ease of movement between the north and the west is necessary for northern-community dolphins to access suitable habitat, and gives new concern to construction projects planned for the region. We emphasize our study as an example of how sociobiological information can be important in understanding human impacts on animal populations.

Impacts of recreational boating activities on the seagrass Posidonia in SE Australia

In SE Australia, the seagrass Posidonia australis is mostly restricted to isolated populations in estuaries and bays, and meadows in Sydney metropolitan estuaries have recently been listed by the NSW Government as threatened with extinction. While large developments impacting on seagrasses are now mostly controlled by environmental legislation, small-scale impacts remain and can lead to fragmentation across large areas. Here, damage to Posidonia meadows caused by boat moorings, propeller scouring and related recreational boating activities has been investigated using easily accessed aerial photography. While individual impacts were often small, in some locations large areas were affected and significant fragmentation of the seagrass landscape was observed and suggests urgent management action is required. The widespread availability of remote sensed data through tools such as Google Earth (©) should lead to greater community awareness of local changes in seagrassses meadows and could be used to improve the management of these smaller scale impacts.

Invasion in tidal zones on complex coastlines: modelling larvae of the non‐native Manila clam, Ruditapes philippinarum, in the UK

AbstractAim To evaluate whether natural larval transport and behaviour alone can explain the pattern of invasion and establishment of the non‐indigenous Manila clam, Ruditapes philippinarum (Adams & Reeve, 1850), and its spread beyond the point of introduction in the UK.Location The study is focused on Poole Harbour, south England, the point of introduction of the Manila clam in the UK.Methods We use fine‐resolution hydrodynamic models coupled with a water salinity model and an individual behaviour model of Manila clam larvae. The model was informed by experimental studies on the vertical response of larvae to salinity and field studies of the species in its natural and new environments.Results Variations in the behavioural response of larvae to salinity in the model considerably affected the retention of clam larvae within the harbour. High levels of predicted larval retention occurred in two of five zones in the harbour when the salinity target was set at 17 practical salinity units. Persistently high densities of adult clams and recruits are accurately predicted in these regions.Main conclusions Even within a relatively small region such as Poole Harbour, there is both localized retention of larvae or ‘closed’ areas and areas that are considerably more ‘open’ and potentially connected. The behavioural response of larvae to salinity significantly affected the degree of retention and ‘openness’ of the harbour to this species. Although, through natural transport, larvae could theoretically reach the next available habitat within the duration of their pelagic stage our study indicates that areas of sufficiently reduced salinity may be necessary for sufficient retention, recruitment and establishment of new adult populations in estuaries. High resolution hydrodynamic models, coupled with larval behaviour, can accurately simulate and predict biological invasion along complex coastlines and contribute to risk assessment of the introduction of non‐indigenous species for aquaculture and spatial management of marine protection.

Growth Modeling and Spatio-Temporal Variability in the Body Condition of the Estuarine Shrimp Palaemon longirostris in the Gironde (Sw France)

Abstract Growth and morphometric characteristics of the caridean Palaemon longirostris Milne Edwards, 1837, were studied in the Gironde estuary population. Their first comparison with earlier studies in this estuary and in the Mira River provided the first step towards developing environmental indicators using a species represented at the European scale. Mean individual growth was modelled for each sex using the classical von Bertalanffy growth model and the seasonal model that integrates periods of lower growth. Morphometric relationships, in particular the spatio-temporal variability in the relative weight of individuals, were explored according to sex and physical parameters of the environment. Females grew to larger size than males. Growth estimates showed the importance of accounting for the seasonal variations to evaluate non-biased growth. Sex and the presence of eggs for females showed significant interaction within the carapace length – total length relation as well as for the carapace length – w...

The Role of Alternate Hosts in the Ecology and Life History of Hematodinium sp., a Parasitic Dinoflagellate of the Blue Crab (Callinectes sapidus)

Hematodinium sp. infections are relatively common in some American blue crab (Callinectes sapidus) populations in estuaries of the western Atlantic Ocean. Outbreaks of disease caused by Hematodinium sp. can be extensive and can cause substantial mortalities in blue crab populations in high salinities. We examined several species of crustaceans to determine if the same species of Hematodinium that infects C. sapidus is found in other crustaceans from the same localities. Over a 2-yr period, 1,829 crustaceans were collected from the Delmarva Peninsula, Virginia, examined for the presence of infections. A portion of the first internal transcribed spacer (ITS1) region of the ribosomal RNA (rRNA) gene complex from Hematodinium sp. was amplified and sequences were compared among 35 individual crustaceans putatively infected with the parasite, as determined by microscopic examination, and 4 crustaceans putatively infected based only on PCR analysis. Of the 18 crustacean species examined, 5 were infected with Hematodinium sp. after microscopic examination and PCR analysis, including 3 new host records, and an additional species was positive only via PCR analysis. The ITS1 rRNA sequences of Hematodinium sp. from the infected crustaceans were highly similar to each other and to that reported from C. sapidus (>98%). The similarity among these ITS1 sequences and similarities in the histopathology of infected hosts is evidence that the same species of Hematodinium found in C. sapidus infects a broad range of crustaceans along the Delmarva Peninsula. Our data indicate that the species of Hematodinium found in blue crabs from estuaries along the east coast of North America is a host generalist, capable of infecting hosts in different families within the Order Decapoda. Additionally, evidence indicates that it may be capable of infecting crustaceans within the Order Amphipoda.

Life strategies of Halobatrachus didactylus (Bloch and Schneider, 1801) in the Tagus estuary: Comparison among different morphotypes

The Lusitanian toadfish, Halobatrachus didactylus (Bloch and Schneider, 1801), is a subtropical sound-producing marine teleost that inhabits estuaries and other brackish water ecosystems in its northern distribution area. The relative isolation of populations within estuaries may cause important modifications in the bio-ecology of this species. The males of this species present two morphotypes which are more accurately distinguishable during the reproductive season. In the Tagus estuary population, the two types of reproductive males were present: type I, the “characteristic” morphotype, and type II, the alternative morphotype. The opportunistic males had more developed testis while type I males had more developed accessory glands. Type I males presented more developed swimbladders and larger body size and live longer than type II males. On the contrary, type II males grew faster and matured earlier. The feeding habits of the two male morphotypes were similar during the reproductive season but differences were found between reproductive specimens and non-reproductive specimens. The diet of reproductive specimens was mainly composed of benthic prey in contrast to predominance of nectobenthic prey in the diet of non-reproductive specimens. The females of H. didactylus generally had an intermediate pattern between the two male morphotypes. The percentage of type II males tended to be higher in denser areas of the estuary. In comparison with populations from different size ecosystems, smaller ecosystems revealed important modifications on the bio-ecology of the species due to the increased competition for nesting sites and mating partners, favouring alternative male tactics.

Use of extractable lipofuscin to estimate age ­structure of ghost shrimp populations in west coast estuaries of the USA

Determining age in crustaceans is inherently imprecise because they molt periodically and do not retain hard structures throughout their lifespan. Morphological measurements are often used to estimate age, but variability in individual growth rate and molt frequency can result in a wide distribution of sizes in a single age class, making size a poor predictor of true age. Concentration of the autofluorescent age pigment, lipofuscin, has been shown to be directly related to actual age in many crustaceans. The present study assessed the potential of using extractable lipofuscin as a method for determining age in the ghost shrimp Neotrypaea californiensis. Following validation of the technique, lipofuscin-based aging was used to determine age structures for 3 populations of N. californiensis, and these were compared to age structures determined using traditional lengthbased methods. Analysis of lipofuscin revealed up to 13 age classes where the size-based analysis showed only 7. Comparison of mean size-at-age among populations in Oregon and Washington estuaries demonstrated that growth rate varied spatially, probably responding to site-specific environmental factors like food availability and population density. N. californiensis negatively impact oyster aquaculture in Pacific Northwest estuaries. Analysis of extractable lipofuscin proved to be a more accurate method of age determination than body-length measurements and should facilitate more indepth investigations of basic biological and ecological processes, which will benefit current efforts to develop an integrated pest management plan for N. californiensis.

Life history of the Indo‐Pacific humpback dolphin in the Pearl River Estuary, southern China

AbstractWe studied life history characteristics of the Hong Kong/Pearl River Estuary population of Indo‐Pacific humpback dolphins (Sousa chinensis), based on data from 120 specimens stranded between 1995 and 2009, 40 individuals biopsied at sea, and a long‐term (14+ yr) photo‐identification study. Ages were determined for 112 specimens by thin‐sectioning teeth and counting growth layer groups. Estimated length at birth was 101 cm. Longevity was at least 38 yr, and there was little difference in growth patterns of males and females. Growth was described by a Bayesian two‐phase Gompertz model; asymptotic length was reached at 249 cm. The tooth pulp cavity filled at an average of 18.5 yr of age. Physical maturity was reached at between 14 and 17 yr of age, apparently a few years after attainment of sexual maturity. Maximum lengths and weights of about 268 cm and 240 kg were attained. Females appear to lose all their spots by 30 yr, although males may retain some spotting throughout life. Calving occurred throughout the year, with a broad peak from March to June. Of 60 females monitored at sea for >14 yr of the study, none were documented to have more than three calves, suggestive of low reproductive output or low calf survival.

Fine‐scale population genetic structuring of bottlenose dolphins in Irish coastal waters

AbstractThe identification of localized discrete populations is particularly important to the management and conservation of animal species, especially in the marine environment, where potential for dispersal is high but barriers to gene flow are often not clear. We investigated population genetic structuring of bottlenose dolphinsTursiops truncatusfound along the west coast of Ireland, with particular attention to the Shannon Estuary, which is the only candidate Special Area of Conservation designated for this species in Irish waters. A genetic structure analysis using 62 biopsy samples from free ranging dolphins and 23 necropsies from stranded dolphins revealed fine‐scale population structure among three distinct populations. The Shannon Estuary population appears to be genetically isolated from adjacent coastal areas, with the exception of four animals sampled from a small group of six dolphins that are now resident in Cork Harbour (south coast) indicating ongoing gene flow or recent dispersal between these two areas. A second genetically distinct aggregation was identified in the Connemara–Mayo region, where recent photo‐identification studies have suggested that dolphins found in this area show a degree of site fidelity. We found moderate nuclear (15 microsatellites) and low mitochondrial (544 bp of the control region) gene diversity in dolphins using the Shannon Estuary and the Connemara–Mayo region, while dolphins that stranded along the coast showed markedly higher levels of gene diversity at both classes of markers. Specifically, these stranded dolphins formed a third genetically distinct cluster, which may be part of a larger pelagic population, as also suggested by the high levels of gene diversity. These results provide new insights into population structure of bottlenose dolphins in Irish waters and will aid future management and conservation of the species in the eastern North Atlantic.

Transport and retention of the mitten crab (<I>Eriocheir sinensis</I>) in a Mid-Atlantic estuary: Predictions from a larval transport model

Invasive species cause extensive ecological damage in freshwater and marine habitats and are a threat to biodiversity in aquatic ecosystems world-wide. One such species, the Chinese mitten crab, Eriocheir sinensis, has invasive populations in northern Europe and San Francisco Bay, and there are confirmed reports of breeding female crabs in both the Chesapeake and Delaware Bays. Despite their threat to these ecosystems, there are still large gaps in the current understanding of this species’ larval biology that are critical to predicting the potential for large populations to establish in East Coast bays and estuaries. We addressed these issues by using a physical circulation model of Delaware Bay and the adjacent coastal ocean coupled to a modified particle advection scheme. We used this model to examine the effects of different physical mechanisms and larval behavior on transport, retention, and settlement of larvae in the bay. The circulation model produced flow fields using observed winds and river discharge for 2006 as well as systematic variations of river discharge and wind direction. Since little is known regarding mitten crab larval behavior, the larval component was purposefully general and incorporated a suite of behaviors such as tidal, diel, and ontogenetic vertical migration; however, results of this study showed that vertical migration affects the magnitude, but not locations of larval settlement. Simulations revealed that changes in the time and location of spawning can result in large variations in retention and settlement of larvae in Delaware Bay and the coastal ocean, due to seasonal variations of the physical flow field. Overall results of our study showed that the estuarine and coastal circulation typically found along the Middle Atlantic coast of the United States can result in significant retention of new and established E. sinensis populations in large estuaries as well as transport of larvae to new coastal locations.