Potential Impact of an Exotic Mammal on Rocky Intertidal Communities of Northwestern Spain

Being the interface of sea and land, the coast can be invaded by introduced species coming from either of these two worlds. Recent reviews of coastal invasions emphasize the human-mediated transport of non-indigenous marine plants and invertebrates, forgetting the potential role of invaders of terrestrial origin. By studying the diet of the introduced American mink (Mustela vison) on a rocky shore of southwestern Europe, we draw attention to the potential impact on intertidal communities of exotic species coming from inland. We analysed 199 mink faeces collected in August 1997 and August 1999 in Baiona, a coastal and urban area of northern Spain recently invaded by minks. The diet of the species was based almost exclusively on crabs (45.4% of individual prey) and fish (53.3%). Most crabs were marbled crabs (Pachygrapsus marmoratus) and most fish were adult blennies (Coryphoblennius galerita and Lipophrys pholis). Given its energy requirements (about 1250 kJ/day), a single mink will consume during the month of August approximately 945 blennies and 496 crabs. Although we lack accurate data on mink abundance, a cautious estimation (4 mink/km before dispersal), supported by field observations, suggests that predation in August may reach 3780 blennies and 1984 crabs per km of shoreline. This predation pressure could affect the numbers of blennies and (less probably) crabs, indirectly benefiting the populations of their prey, that is, sessile invertebrates and snails. More field research is needed, but our results suggest that an exotic non-marine top predator such as the American mink could affect intertidal communities in Eurasia.     

First Report of the Asian kelp Undaria pinnatifida in the Northeastern Pacific Ocean

The Asian kelp Undaria pinnatifida was discovered in southern California in the spring of 2000, and by the summer of 2001 had been collected at several California sites from Los Angeles to Long Beach Harbors and Catalina Island as far north as Monterey Harbor. From its native range in the northwestern Pacific, Undaria has now been introduced to the northeastern and southwestern Atlantic and the southwestern and northeastern Pacific, through a combination of intentional transport for cultivation, accidental transport with oysters, as fouling on vessel hulls, and possibly other means. In the northeastern Pacific, water temperatures are suitable for its establishment from at least Baja California to British Columbia, where it is likely to grow well in sheltered and partially sheltered waters.     

The Round Goby, Neogobius melanostomus, a Fish Invader on both sides of the Atlantic Ocean

During the past decade, a bottom-dwelling, aggressive, multiple-spawning fish, the round goby (Gobiidae: Neogobius melanostomus), has spread from its native region in the Ponto-Caspian throughout Europe and to the Laurentian Great Lakes in North America. An international workshop, held at the Hel Marine Station, Poland, was organized to summarize population features of the round goby. Common fish predators of round gobies in the Great Lakes and in native regions are obligate and facultative benthic fishes and occasionally, pelagic fishes. In contrast, the main predator of the round goby in the Gulf of Gdansk is the Great Cormorant (Phalacrocorax carbo). In the Great Lakes, round gobies have lead to the decline of mottled sculpin (Cottus bairdi) and logperch (Percina caprodes) and reduced the hatching success of native fishes by feeding on their eggs. In the Gulf of Gdansk, round gobies have increased in abundance, while three-spined sticklebacks (Gasterosteus aculeatus) have declined. Round gobies have a broad diet throughout their range; larger specimens are molluscivores. There are fewer species of parasites and lower infection rates of round gobies in recently colonized areas than in native areas. Overall, newly colonized round gobies in brackish waters and lakes are smaller, mature earlier, have a male biased operational sex ratio and are more short-lived compared with round gobies from marine (native) habitats.     

Temporal variation in abundance of the egg predator Carcinonemertes epialti (Nemertea) and its effect on egg mortality of its host,the shore crab,Hemigrapsus oregonensis

An outbreak of the nemertean, Carcinonemertes epialti, was observed on Hemigrapsus oregonensis during October, 1982 at Campbell Cove, Bodega Harbor, California. Mean worm intensity (296 worms/crab) was the highest recorded for this nemertean egg predator on H. oregonensis. During the outbreak, male crabs were found to harbor more worms than both non-ovigerous and ovigerous females. Crab egg mortality was substantial; 83% of the ovigerous females experienced 75–100% brood mortality. The seasonal peak in worm abundance coincided with the seasonal low in crab reproduction at this locality. A method for estimating the impact of C. epialti on H. oregonensis natality was developed using crab size and fecundity, and worm prevalence and intensity. For a non-outbreak sampling period, a mean of 5.6% egg mortality was experienced by infested crabs for the period selected. Thus, brood mortality during the outbreak was much greater than that experienced at non-outbreak periods. Heavy fishing pressure on some commercially important crab species has been suggested as a possible factor inducing worm outbreaks and facilitating their continued persistence. These observations suggest that fisheries are not necessarily responsible for the outbreaks of nemerteans on commercially important crab species. However, fishing pressure may still be a sufficient condition to promote nemertean outbreaks.     

Occurrence and diversity of mesophilic Shewanella strains isolated from the North-West Pacific Ocean

Although bacteria of the genus Shewanella belong to one of the readily cultivable groups of "Gammaproteobacteria", little is known about the occurrence and abundance of these microorganisms in the marine ecosystem. Studies revealed that of 654 isolates obtained from marine invertebrates (ophiuroid Amphiopholis kochii, sipuncula Phascolosoma japonicum, and holothurian Apostichopus japonicus, Cucumaria japonica), seawater and sediments of the North-West Pacific Ocean (i.e. the Sea of Japan and Iturup Is, Kurile Islands), 10.7% belonged to the genus Shewanella. The proportion of viable Shewanella species varied from 4% to 20% depending on the source of isolation. From the isolation study, representative strains of different phenotypes (from seventy presumptive Shewanella strains) were selected for detailed characterization using phenotypic, chemotaxonomic, and phylogenetic testing. 16S rDNA sequence-based phylogenetic analysis confirmed the results of tentative identification and placed the majority of these strains within only a few species of the genus Shewanella with 98-99% of 16S rDNA sequences identity mainly with S. japonica and S. colwelliana, suggesting that the strains studied might belong to these species. Numerically dominant strains of S. japonica were metabolically active and produced proteinases (gelatinases, caseinases), lipases, amylases, agarases, and alginases. Shewanella strains studied demonstrated weak antimicrobial and antifungal activities that might be an indication of their passive role in the colonization on living and non-living surfaces.     

Rotifer distributions in the coastal waters of the northeast Pacific Ocean

Absolute abundance of rotifers was assessed from 5 to 80 km across the continental shelf off of the southern Oregon coast (U.S.A.) in the northeast Pacific Ocean. A total of 97 vertically stratified water samples were collected at 49 stations from two depths, 3 and 30 m. Coastal upwelling conditions were indicated, with decreased temperature, increased salinity and higher chlorophyll-a concentrations closer to shore. Two rotifer genera, Synchaeta and Trichocercaoccurred within 16 km of shore with densities increasing closer to shore. Synchaeta reached densities of 64 inds l^–1 while Trichocerca was sparse (<1 inds. l^–1). Rotifers were most abundant at 3 m and the densest aggregations appear to be associated with estuary outlets, suggesting that estuaries may be important in exporting rotifers to nearshore coastal waters.     

Influence of predator density on nonindependent effects of multiple predator species

Interactions between multiple predator species are frequent in natural communities and can have important implications for shared prey survival. Predator density may be an important component of these interactions between predator species, as the frequency of interactions between species is largely determined by species density. Here we experimentally examine the importance of predator density for interactions between predator species and subsequent impacts on prey. We show that aggressive interactions between the predatory shore crabs Carcinus maenas and Hemigrapsus sanguineus increased with predator density, yet did not increase as fast as negative interactions between conspecifics. At low density, interactions between conspecific and heterospecific predators had similar inhibitory impacts on predator function, whereas conspecific interference was greater than interference from heterospecifics at high predator density. Thus the impact of conspecific interference at high predator density was sufficient in itself that interactions with a second predator species had no additional impact on per capita predation. Spatial and temporal variability in predator density is a ubiquitous characteristic of natural systems that should be considered in studies of multiple predator species.     

Feeding habits of the predaceous nymphs of Dolania Americana in Northwestern Florida (Ephemeroptera : Behningiidae)

Feeding habits of nymphs of the predatory mayflyDolania americana Edmunds & Traver in northwestern Florida were examined during 1971 and 1972. Larvae of Chironomidae (Diptera) formed the bulk of prey items. The size of the predaceousD. americana nymphs was correlated with the size of chironomid prey taken. Differential microhabit utilization allows partition of prey resources with the other major predator species present. The relationship between predator and prey biomass throughout the year is discussed.     

Long-term changes in the population size and geographical distribution of Pennella sp. (Copepoda) on the saury,Cololabis saira,in the western North Pacific Ocean and adjacent seas

Changes in the population size and geographical distribution of the mesoparasitic copepod Pennella sp. (Siphonostomatoida: Pennellidae) on the saury, Cololabis saira, were studied for a period of six years (1981–86) in the western North Pacific Ocean and adjacent seas. The parasite was first recorded in the western North Pacific in 1981. Its population size increased rapidly in 1982–83 and declined slightly in 1984. During these years, infected fish were widely distributed in the western and central North Pacific and also found in the Sea of Okhotsk and the Sea of Japan. However, the population declined dramatically in 1985 and its distributional range was reduced. The parasite disappeared in 1986. The observed frequency distributions of parasites on the host population were the Poisson in 1981 and 1985, but those during 1982–1984 were over-dispersed and fitted the negative binomial.Parasites of the saury, Cololabis saira (Brevoort)-IV.     

Molecular and ultrastructural characterization of two ascomycetes found on sunken wood off Vanuatu Islands in the deep Pacific Ocean

A new genus of a deep-sea ascomycete with one new species, Alisea longicolla, is described based on analyses of 18S and 28S rDNA sequences and morphological characters. A. longicolla was found together with Oceanitis scuticella, on small twigs and sugar cane debris trawled from the bottom of the Pacific Ocean off Vanuatu Islands. Molecular and morphological characters indicate that both fungi are members of Halosphaeriaceae. Within this family, O. scuticella is phylogenetically related to Ascosalsum and shares similar ascospore morphology and appendage ontogeny. The genus Ascosalsum is considered congeneric with Oceanitis and Ascosalsum cincinnatulum, Ascosalsum unicaudatum and Ascosalsum viscidulum are transferred to Oceanitis, an earlier generic name.     

Thoughts on the ecology and evolution of the intertidal biota of the Azores and other Atlantic islands

The special features of the intertidal ecosystems of remote islands are reviewed briefly before focusing on the littoral zone of Macaronesia (Azores, Madeira and Canaries). Distribution patterns are briefly compared with other European shores. Species missing from the Azores compared with Madeira, the Canaries and continental European shores are listed. The degree of genetic differentiation within and amongst selected important species of gastropods (Patella spp.) and barnacles (Chthamalus spp.) in Macaronesia is reviewed. The role of isolated islands in allopatric speciation of these organisms is discussed in relation to dispersal. Possible threats to the populations and communities of rocky shores in Macaronesia are considered in the context of the endemic nature of certain species. The importance of studies of basic ecology and genetics to inform resource management and conservation is highlighted. Future research directions are indicated, emphasizing the usefulness of Macaronesia as a model system to explore speciation in intertidal organisms.     

Adaptations for feeding on rock surfaces and sandy sediment by the fiddler crabs (Brachyura: Ocypodidae) Uca tetragonon(Herbst, 1790) and Uca vocans(Linnaeus, 1758)

Two species of fiddler crab, Uca tetragonon(Herbst, 1790) and Uca vocans(Linnaeus, 1758), which belong to the subgenus Gelasimus, dwell on rocky shores and muddy–sandy tidal flats, respectively, in Phuket Is., Thailand. We investigated their feeding ecology in relation to the morphology of their feeding organs: minor food-handling chelipeds and maxillipeds. U. tetragononfed chiefly on rocks covered by filamentous green algae. U. vocansfed on the emerged sand and in shallow water along the shoreline and in pools. While feeding, both crabs made sand pellets beneath their mouthparts and discarded them, indicating that they divided the matter scooped up with their minor chelipeds into edible and inedible fractions by using the maxillipeds in the water passing through their buccal cavity. The morphology of maxillipeds hardly differed between the two species, which means that both species are flotation-feeders. The morphology of their minor chelipeds, however, differed: the tips of the dactyl and pollex were flat in U. tetragononand pointed in U. vocans.When the minor cheliped was closed, U. tetragononhad a hemispherical space in the distal one-fourth of the gape, which was closed by the framing keratin layers and a few setae of the dactyl and pollex. On the other hand, U. vocanshad an ellipsoidal space in the distal half of the gape. We consider these morphological characters to be adaptations to the different feeding substrates for retaining more food-laden sediment. We discuss the role of the setae on the minor chelipeds on the basis of the morphological differences between populations of U. tetragononin Phuket Is. and East Africa where the crab inhabits muddy–sandy tidal flats.     

The reproductive biology of two deep-water,reef-building scleractinians from the NE Atlantic Ocean

The reproductive ecology of colonies of Lophelia pertusa (Linné 1758) and Madrepora oculata Linné (1758) from the Porcupine Seabight (Thérèse Mound and South Porcupine Seabight site) and the Darwin Mounds (NE Rockall Trough—L. pertusa only) was investigated using histological techniques. Samples of L. pertusa exhibited seasonal reproduction, whereas the evidence for M. oculata is equivocal but suggests multiple cohorts of gamete production. L. pertusa produces a single cohort of around 3,000 oocytes, whereas M. oculata produces two cohorts, with a total fecundity of around 60 oocytes. The maximum observed oocyte size in L. pertusa was 140 μm and in M. oculata was 405 μm. From these oocyte sizes and the timing of reproduction, a lecithotrophic larva is expected, though not observed. This seasonality of reproduction fits with the phytodetrital food fall occurring around July in the Seabight area. L. pertusa was found to be non-reproductive at the Darwin Mound site. Though unable to be specifically tested, this may suggest that the increased trawling activity in this area might be keeping colonies below sexually viable sizes, as seen in numerous shallow water situations. All areas in the NE Atlantic are coming under threat from increased fishing and commercial exploration practices. This study shows that these highly seasonal reproducers could be sensitive to these fishing operations and care must be taken so as not to repeat the destruction that has occurred on shallower reefs.     

The predation on Asellus aquaticus (L.) by perch,Perca fluviatilis (L.), in a small forest lake

Asellus aquaticus (L.) was the most important benthic food item for perch, Perca fluviatilis (L.), in a small, extremely humic forest lake in southern Finland. The proportion of A. aquaticus in the diet of perch varied according to the former's availability, which, in turn, depended on its life cycle. Perch 11.0–12.9 cm (total length) most frequently fed on A. aquaticus; smaller and larger perch fed more frequently on crustacean zooplankton and aquatic insect larvae, respectively. The high density of the perch population, the importance of A. aquaticus in the benthos of the study lake and the general high activity level of the prey resulted in a high predation (0.1–1.8% per day). The population of A. aquaticus was also limited by the scarcity of macrophytic vegetation and the small area of oxygenated littoral in the lake.     

Assessment of Potential Impacts of Exotic Species on Populations of a Threatened Species, White Sands Pupfish, Cyprinodon tularosa

The potential impact of introduced species on rare taxa is of particular concern to conservation biologists. We evaluate the impacts of western mosquitofish (Gambusia affinis) and virile crayfish (Orconectes virilis) on experimental populations of a threatened species, the White Sands pupfish (Cyprinodon tularosa). Forty experimental pupfish populations were exposed to one of four treatments; (a) 1 crayfish, (b) 4 crayfish, (c) 5 adult mosquitofish and (d) control. Pupfish population size and biomass was monitored over the duration of one breeding season. A repeated measure multiple analysis of covariance revealed a significant effect of treatments on response variables (population size and biomass) (P<0.0001). Mosquitofish had a significant effect on population size and biomass (P=0.0330). The effect of one crayfish was not significant (P=0. 0683). However, 4 crayfish had a significant effect (P<0.0001) on population size. We use these data, along with information on environmental tolerances of crayfish and mosquitofish, to evaluate risks for specific pupfish populations. An erratum to this article is available at .     

Systematic Status of Bonefishes (Albula spp.) From the Eastern Pacific Ocean Inferred from Analyses of Allozymes and Mitochondrial DNA

Recent molecular evidence suggests that at least eight species of bonefishes (Albuliformes: Albulidae: Albula) are found worldwide (Colborn et al. 2001). Adults of most of these species, including two that are restricted to the eastern Pacific Ocean (Albula sp. A from the Gulf of California and Albula sp. C from the Gulf of Panama), have not been formally described. Because cryptic species of bonefishes are known to occur sympatrically, population genetics data provide an important tool for taxonomic studies on this group. Isozyme analyses conducted on larval, juvenile and adult bonefish from the Guaymas region of the central Gulf of California confirmed that only a single species (Albula sp. A) was present there. In addition, analysis of a segment of the cytochrome b gene from three adult Albula collected from coastal waters of southern California revealed high sequence homology with Albula sp. A, suggesting that the southern California specimens were conspecific with those from Guaymas. However, the southern distributional limit of Albula sp. A, and whether there are regions where Albula sp. A and C occur sympatrically, are unknown. The historical background of the available name Atopichthys esunculus Garman, 1899 [= Albula esuncula (Garman, 1899)], and problems associated with the nomenclature of the two species of eastern Pacific bonefishes, are summarized. The systematic status of the related shafted bonefish, Dixonina (= Albula) nemoptera Fowler, 1911, is also reviewed.     

Molecular phylogeography of Ruditapes philippinarum in the Northwestern Pacific Ocean based on COI gene

To examine the pattern of phylogeography of Ruditapes philippinarum, a length of 644-bp gene fragment of the mtDNA COI was sequenced. A total of 170 individuals from 19 locations were analyzed yielding 74 haplotypes, most of which were unique. The levels of haplotype diversity and nucleotide diversity for the species ranged from 0.80 ± 0.16 (Notsuke Bay) to 1.00 ± 0.13 (Nanao Bay, Miyazu Bay, Dalian 1 and Ariake), and from 0.002 ± 0.001 (Notsuke Bay) to 0.011 ± 0.006 (Qingdao), respectively. Both the phylogenetic (NJ tree) and minimum spanning trees (MST) showed three significant genealogical clusters corresponding to sampling localities, a genetic differentiation speculated to be caused by the isolation of the marginal seas of the Northwestern Pacific during Pleistocene low sea-level stands. Both AMOVA and pairwise Fst analyses revealed significant genetic differentiation between the populations from Japan and China. The pattern of isolation by distance was also detected in this species (r = 0.50, P < 0.001). Both mismatch distribution analysis and the neutrality tests showed that R. philippinarum had undergone a recent population expansion. The estimate of population expansion time was about 425 kya-1580 kya.     

Impacts of mosquitofish (Gambusia affinis) predation on plankton communities

An investigation of the effects of mosquitofish (Gambusia affinis) predation was conducted in 12 experimental ponds in southern California over a period of 10 months.Gambusia essentially eliminatedDaphnia pulex andCeriodaphnia sp. populations, reducedDiaptomus pallidus andKeratella quadrata populations, had little impact onCyclops vernalis, and caused large increases inK. cochlearis, Polyarthra sp.,Synchaeta sp., andTrichocerca spp. populations and in total phytoplankton.Gambusia caused a decrease in the PIE (probability of interspecific encounter) of the planktonic crustaceans and an increase in the PIE of the planktonic rotifers. Hemiptera, such as neustonicMicrovelia sp. and nektonicBuenoa sp. andNotonecta sp., andHyla regilla tadpoles were absent from fish ponds but sometimes abundant in control ponds.Gambusia caused higher pH and oxygen levels, presumably via its effect on the phytoplankton. The impact ofGambusia on the pond ecosystems was less in winter, when fish numbers and feeding rates were low, than in summer. Results of other fish-plankton studies are summarized in tabular form. A model is proposed to account for variation in the calanoid/cyclopoid ratio; evidence is summarized suggesting that in general calanoids are more susceptible to predation by predaceous zooplankters while cyclopoids are more susceptible to fish predation. Some parallels are drawn between the effects ofGambusia predation and those of insecticide treatments.     

Invasion of a Reef-builder Polychaete: Direct and Indirect Impacts on the Native Benthic Community Structure

In this work, we evaluate the effect of the introduced reef-building polychaete Ficopomatus enigmaticus on the benthic community and on sediment characteristics of a southwestern Atlantic coastal lagoon. When reefs were experimentally added, density of the native crab Cyrtograpsus angulatus dramatically increased in a short time period. After reefs and crabs were experimentally transplanted as a unit, they decreased the density of the free-living soft-bottom polychaetes Heteromastus similis and Laeonereis acuta. Exclusion/inclusion caging experiments showed that Cyrtograpsus negatively affect the density of soft-bottom polychaetes (H. similis, L. acuta, Nephtys fluviatilis) and ostracodes. Our results showed that this effect is much higher in areas populated by reefs because of the increased density of crabs that find shelter under the reefs. Thus, reefs have a cascading effect on the native benthic community within the areas colonized by them. Analysis of crab stomach contents indicated that crabs feed on a wide variety of prey, including infaunal organisms, small gastropods and also algae. When reefs and crabs were experimentally added, the amount of bivalve shells on superficial sediments increased. Our results suggest that this bivalve shell accumulation and sediment composition are due to the reworking activity of Cyrtograpsus in the sediment where they dig burrows. The invasive habits of Ficopomatus may be favoring crabs to have a major effect on the integrity of the native community in the lagoon. Ficopomatus should be considered a bioengineer organism by creating and regulating refuge for other species, altering the interactions between preexistent species and also by changing the physical factors of the invaded environment.