Differentiation and adaptive radiation of amphibious gobies (Gobiidae: Oxudercinae) in semi-terrestrial habitats

During several surveys made in the region of the lower Fly River and delta, Papua New Guinea, nine species of oxudercine gobies (Gobiidae: Oxudercinae) were recorded: Boleophthalmus caeruleomaculatus, Oxuderces wirzi, Periophthalmodon freycineti, Periophthalmus darwini, Periophthalmus novaeguineaensis, Periophthalmus takita, Periophthalmus weberi, Scartelaos histophorus and Zappa confluentus. An exploratory multivariate analysis of their habitat conditions discriminated five guilds, differentially distributed in habitats with different quantities of environmental water and three guilds corresponding to different levels of salinity. A partial correspondence between phylogenetic and ecological categories suggested the presence of parallel adaptive radiations within different genera. In particular, the species found in the most terrestrial habitats (P. weberi) was also found in the widest range of conditions, suggesting that colonization of extreme semi-terrestrial and freshwater habitats by this species was facilitated by eurytypy. It is proposed that these findings provide insight into convergent adaptations for the vertebrate eco-evolutionary transition from sea to land.     

The Loss of Genetic Diversity in Sichuan Taimen as Revealed by DNA Fingerprinting

Species endangerment often derives from the “endangerment” of genetic diversity, thus loss of genetic diversity is an important cause of species extinction. Since historical specimens were unavailable, previous studies mainly described the genetic diversity status in the current population rather than the loss of genetic variation over time. In this study, we collected samples during1998–1999 and obtained historical specimens from 1957 to 1958. Based on the two sets of fish, we determined the changes in genetic diversity of Sichuan taimen using DNA fingerprinting. The differences in genetic parameters between the present samples and historical taimens revealed their loss of genetic variation. As a result, the existing populations have lower viability, and proper management has to be implemented to preserve genetic diversity.     

Evaluation of the 16S and 12S rRNA genes as universal markers for the identification of commercial fish species in South Africa

The development of DNA-based methods for the identification of fish species is important for fisheries research and control, as well as for the detection of unintentional or fraudulent species substitutions in the marketplace. The aim of this study was to generate a comprehensive reference database of DNA sequences from the mitochondrial 16S and 12S ribosomal RNA (rRNA) genes for 53 commercial fish species in South Africa and to evaluate the applicability of these genetic markers for the identification of fish at the species level. The DNA extracted from all target species was readily amplified using universal primers targeting both rRNA gene regions. Sequences from the 16S and 12S rRNA genes were submitted to GenBank for the first time for 34% and 53% of the fish species, respectively. Cumulative analysis of the 16S rRNA gene sequences revealed mean conspecific, congeneric and confamilial Kimura two parameter (K2P) distances of 0.03%, 0.70% and 5.10% and the corresponding values at the 12S level were 0.03%, 1.00% and 5.57%. K2P neighbour-joining trees based on both sequence datasets generally clustered species in accordance with their taxonomic classifications. The nucleotide variation in both the 16S and 12S sequences was suitable for identifying the large majority of the examined fish specimens to at least the level of genus, but was found to be less useful for the explicit differentiation of certain congeneric fish species. It is recommended that one or more faster-evolving DNA regions be analysed to confirm the identities of closely-related fish species in South Africa.     

Spawning migration of American eel Anguilla rostrata from pristine (1843-1872) to contemporary (1963-1990) periods in the St Lawrence Estuary, Canada

A key for three putative species apparently found in three geographic areas, i.e. Coregonus clupeoides (in Scotland), Coregonus stigmaticus (in England), and Coregonus pennantii (in Wales) given in a recent review was tested quantitatively using 544 individuals from nine populations. The classification success of the key was very low (27%). It was concluded that there is currently no robust evidence for the recognition of the three putative species. Furthermore, the use of phenotypic characters alone to distinguish putative species in postglacial fish species such as those of the genus Coregonus that show homoplasy in many of these traits is questioned. In the absence of further evidence, it was concluded that a single highly variable species best describes the pattern of phenotypic variation in these U.K. populations. On this basis it is argued that taxonomic subdivision of U.K. European coregonids is inappropriate and that Coregonus lavaretus should prevail as the species name applicable to all populations.     

A new species of parasitic copepod, Sarcotretes umitakae sp. n. (Siphonostomatoida,Pennellidae), on the rattail (Actinopterygii,Macrouridae) from?the?East?China Sea,Japan

A new species of copepod, Sarcotretes umitakae sp. n., of the siphonostomatoid family Pennellidae is described based on female specimens from the rattail Coelorinchus jordani Smith and Pope (Actinopterygii: Gadiformes: Macrouridae) caught in the East China Sea. This species is characterized by exhibiting the following characters: the large proboscis projects strongly; the head bears paired lateral processes which are bulbous and taper into a slender horn; the twisting neck is significantly longer than the trunk; and the trunk bears an anterior constriction with a reduced abdomen.     

Post-larval French grunts (Haemulon flavolineatum) distinguish between seagrass, mangrove and coral reef water: Implications for recognition of potential nursery habitats

Environmental cues like sound, magnetic field, oceanic currents, water chemistry or habitat structure are believed to play an important role in the orientation of reef fish towards their settlement habitat. Some species of coral reef fish are known to use seagrass beds and mangroves as juvenile habitats. Once oceanic larvae of these fish have located a coral reef from the open ocean, they still have to find embayments or lagoons harbouring these juvenile habitats. The sensory mechanisms that are used for this are still unknown. In the present study, experiments were conducted to investigate if recruits of the French grunt (Haemulon flavolineatum) respond to habitat differences in water type, as mangrove/seagrass water may differ in biotic and abiotic compounds from coral reef water. Our results show that post-larvae of a reef fish that is highly associated with mangroves and seagrass beds during its juvenile life stage, choose significantly more often for water from mangroves and seagrass beds than for water from the coral reef. These results provide a more detailed insight in the mechanisms that play a role in the detection of these juvenile habitats.     

Potential impacts of climate change on the distributions of several common and rare freshwater fishes in Canada

Climate change will ultimately affect the supply and quality of freshwater lakes and rivers throughout the world. This study examines the potential impacts of climate change on freshwater fish distributions in Canada. Climate normals data (means from 1961 to 1990) from Environment Canada were used to map current climate found throughout the tertiary watersheds of Canada. Logistic regressions based on these climate data were used to develop predictive presence‐absence equations for (a) common commercially and recreationally important species and (b) an Arctic freshwater species and a freshwater fish species of conservation significance listed by the Committee on the Status of Endangered Wildlife (COSEWIC). The Canadian Centre for Climate Modelling and Analysis Global Coupled Model 2(IS92a) provided forecasts of Canada's climate in 2020 and 2050. The data from this scenario and the logistic regressions provided a ready framework for predicting the potential distributions of the fishes. Physical and ecological barriers would have to be overcome for the distribution of these species to actually change in response to climate change. Generally, coldwater species may be extirpated from much of their present range while cool and warm‐water species may expand northward. Species that are limited to the most southern regions of the country may expand northwards. A conceptual framework for assessing potential climate change impacts on fishes and the variety of management strategies required to deal with these impacts are discussed. Our forecasts demonstrate the need for climate change assessments in species at risk as well as for common species.     

Similarities in Behavioral Ecology among Amphidromous and Catadromous Fishes on the Oceanic Islands of Hawai'i and Guam

About seven families of fishes occur routinely in fresh water on oceanic high islands of the tropical Pacific; others (sharks, jacks, bonefish, etc.) are occasional visitors. However, amphidromous fishes (freshwater adults, marine larvae) of the families Gobiidae and Eleotridae are predominant in island streams. Hawai'i, representing the northernmost extent of Polynesia, has five species of gobioid fishes whose adults are limited to fresh water, but Guam, in the Mariana Islands of the far Western Pacific, has more than four times that number. Hawaiian stream fishes are strikingly similar to their Guamanian relatives in their distribution, ecology, and behavior. At both localities, these fishes typically exhibit strong species specificity in the section of stream inhabited by adults, in the microhabitat selected, and in their food and feeding. Although incompletely understood, aspects of the life cycles of amphidromous island fishes (spawning, migrations into and from the sea, and others) are cued by seasonal and short-term changes in stream flow. In the Hawaiian Islands, water-use decisions based on the imperatives of allowing no net loss of habitat for aquatic animals and maintaining stream-ocean pathways for migrating animals have facilitated both management and conservation of diversity in island streams.