Biogeography and the structure of coral reef fish communities on isolated islands

Aim To determine the applicability of biogeographical and ecological theory to marine species at two remote island locations. This study examines how biogeography, isolation and species geographic range size influence patterns of species richness, endemism, species composition and the abundance of coral reef fishes. Location Christmas Island and the Cocos (Keeling) Islands in the tropical eastern Indian Ocean. Methods Published species lists and underwater visual surveys were used to determine species richness, endemism, species composition and abundance of reef fishes at the islands. These data were statistically compared with patterns of species composition and abundance from the neighbouring ‘mainland’ Indonesian region. Results The two isolated reef fish communities were species‐poor and contained a distinct taxonomic composition with an overrepresentation of species with high dispersal potential. Despite low species richness, we found no evidence of density compensation, with population densities on the islands similar to those of species‐rich mainland assemblages. The mix of Indian and Pacific Ocean species and the proportional representations of the various regional faunas in the assemblages were not influenced by the relative proximity of the islands to different biogeographical provinces. Moreover, species at the edge of their range did not have a lower abundance than species at the centre of their range, and endemic species had substantially higher abundances than widespread species. At both locations, endemism was low (less than 1.2% of the community); this may be because the locations are not sufficiently isolated or old enough to promote the evolution of endemic species. Main conclusions The patterns observed generally conform to terrestrial biogeographical theory, suggesting that similar processes may be influencing species richness and community composition in reef fish communities at these remote islands. However, species abundances differed from typical terrestrial patterns, and this may be because of the life history of reef fishes and the processes maintaining isolated populations.     

Trophic resource partitioning among five flatfish species (Actinopterygii, Pleuronectiformes) in a tropical bay in south-eastern Brazil

Five species of flatfishes in a tropical bay in south-eastern Brazil were studied to test the hypothesis that resource partitioning along the spatial and size dimensions has been used as a mechanism to enable coexistence. Three zones in the study area were defined according to environmental characteristics (inner, middle and outer). Sampling was conducted by otter trawl tows during daylight hours, between October 1998 and September 1999. Achiridae species ( Achirus lineatus and Trinectes paulistanus ) showed narrow niche width, indicating a specialized feeding strategy, preying on Polychaeta, and occurring mainly in the inner bay zone. Paralichthyidae ( Citharichthys spilopterus and Etropus crossotus ) and the Cynoglossidae ( Symphurus tessellatus ) showed broad niche width and a generalized feeding strategy preying on a large number of Crustacea. Symphurus tessellatus did not change diet with size-dimension feeding on Amphipoda and Polychaeta, whereas C. spilopterus and E. crossotus shifted diet with growth. Citharichthys spilopterus fed mainly on Mysida and secondarily on shrimps, with juvenile preying on large amounts of Calanoida, whereas adults consumed large amounts of fishes. Isaeidae amphipods were a significant prey for both small and large E. crossotus , whereas Polychaeta Errantia were used mainly by large fishes. Etropus crossotus and S. tessellatus share similar feeding resources in outer bay zone preying on Isaeidae and Polychaeta Errantia. Differences in the Pleuronectiformes diet composition along with spatial and size changes in the use of the available resources contributed to allow the organisms' coexistence in Sepetiba Bay. The high item diversity used by flatfishes indicates that the system plays an important role as a feeding ground, and that interspecific competition for food was unlikely.     

The late Pleistocene desiccation of Lake Victoria and the origin of its endemic biota

A brief review is provided in some advances in understanding the ecology of pike Esox lucius Linnaeus over the last 10 years. Based on long-term studies and manipulative, often short-term experiments (laboratory, field and mesocosms) several established theories have been supported, as well as new concepts developed. Despite their wide distribution pike show low levels of polymorphism and divergence indicative of a recent common ancestral population. Recent genetic studies, however, indicate a single refugium in North America compared to several refugia in Europe. Pike are found in rivers, lakes and weakly saline waters. Variables such as growth and mortality are mainly affected by factors such as temperature, water transparency, productivity, availability of prey and density of pike and other predators. In choice of habitat pike have been shown to support the ideal free-distribution theory. The importance of macrophyte habitat in the life history of pike has been reconfirmed and pike have been shown to be flexible in response to water clarity. Pike are extremely ‘plastic’ in choice of prey types, prey size and in response to prey behaviour (e.g. they are unaffected by shoal size). Predation by pike not only affects abundance and biomass of prey (including younger and smaller pike through cannibalism which plays a major role in population dynamics, other fishes and invertebrates) but also evolution and adaptation of their morphology (in particular body shape) and behaviours. There appears to be no relationship between stock and recruitment. Recruitment is influenced by several abiotic factors in lakes and rivers. Pike play a major role in structuring freshwater communities and have been used in stocking programmes to improve water quality (biomanipulation). Many new concepts have been developed in pike behaviour in maximizing these stocking programmes both in biomanipulation and fisheries management. Despite many recent advances in understanding the ecology of pike, particularly at the individual level, developments in quantifying and modelling the role of pike as a top predator in large ecosystems have been limited, probably due to the difficulties of sampling natural populations. Guest editors: J. M. Farrell, C. Skov, M. Mingelbier, T. Margenau & J. E. Cooper International Pike Symposium: Merging Knowledge of Ecology, Biology, and Management for a Circumpolar Species     

Multi-locus phylogenetic analyses support the monophyly and the Miocene diversification of Iksookimia (Teleostei: Cypriniformes: Cobitidae)

The genus Iksookimia contains six species of primary freshwater fishes that are endemic to South Korea. Previous phylogenetic studies, based on DNA sequence data from three or fewer loci, have suggested non-monophyly of the genus, providing inconsistent resolutions of the relationships of Iksookimia. Our coalescent and concatenation-based phylogenetic analyses, utilizing seven unlinked nuclear-encoded genes, strongly supported Iksookimia as a monophyletic group, emphasizing the importance of multi-locus data in investigating complicated phylogenetic relationships. A relaxed molecular clock analysis using fossil calibrations, indicated that the origin of the major lineages of Iksookimia occurred between ～12 to 5 Ma, which is consistent with the Miocene uplift of the Taebaek and Sobaek Mountains and the Miocene activation of the major south-eastern faults. These palaeogeographic events may have served as vicariant events in the diversification of Iksookimia.     

Length‐weight and length‐length relationships of four small fishes from the Atrai River,Dinajpur, Bangladesh

Length‐weight (LWRs) and length‐length relationships (LLRs) were determined for four fish species collected from the Atari River in Dinajpur of Bangladesh. Sampling took place monthly between January and June 2016, using seine nets of commercial fishermen (mesh size 4 mm). In LWRs (r² > .927, p < .05), slope (b) was estimated as 3.191, 2.992, 3.217 and 3.109 for Acanthocobitis botia, Botia lohachata, Canthophrys gongota and Chanda nama, respectively. In LLRs (r² > .812, p < .05), lengths i.e. TL, SL, HL and FL were highly correlated. The present study on these species would be the baseline for FishBase dataset.     

Using fuzzy logic to determine the vulnerability of marine species to climate change

Marine species are being impacted by climate change and ocean acidification, although their level of vulnerability varies due to differences in species' sensitivity, adaptive capacity and exposure to climate hazards. Due to limited data on the biological and ecological attributes of many marine species, as well as inherent uncertainties in the assessment process, climate change vulnerability assessments in the marine environment frequently focus on a limited number of taxa or geographic ranges. As climate change is already impacting marine biodiversity and fisheries, there is an urgent need to expand vulnerability assessment to cover a large number of species and areas. Here, we develop a modelling approach to synthesize data on species‐specific estimates of exposure, and ecological and biological traits to undertake an assessment of vulnerability (sensitivity and adaptive capacity) and risk of impacts (combining exposure to hazards and vulnerability) of climate change (including ocean acidification) for global marine fishes and invertebrates. We use a fuzzy logic approach to accommodate the variability in data availability and uncertainties associated with inferring vulnerability levels from climate projections and species' traits. Applying the approach to estimate the relative vulnerability and risk of impacts of climate change in 1074 exploited marine species globally, we estimated their index of vulnerability and risk of impacts to be on average 52 ± 19 SD and 66 ± 11 SD, scaling from 1 to 100, with 100 being the most vulnerable and highest risk, respectively, under the ‘business‐as‐usual' greenhouse gas emission scenario (Representative Concentration Pathway 8.5). We identified 157 species to be highly vulnerable while 294 species are identified as being at high risk of impacts. Species that are most vulnerable tend to be large‐bodied endemic species. This study suggests that the fuzzy logic framework can help estimate climate vulnerabilities and risks of exploited marine species using publicly and readily available information.     

Osteology and phylogenetic interrelationships of sturgeons (Acipenseridae)

Sturgeons (Acipenseridae) are an ancient and unique assemblage of fishes historically important to discussions of actinopterygian evolution. Despite their basal position within Actinopterygii, rigorous comparative morphological studies of acipenserids have never been made, and most ideas about acipenserid evolution hinge on an untested impression that shovelnose sturgeons (Scaphirhynchini) are phylogenetically primitive. This impression promoted ideas that: (1) the earliest acipenserids were highly benthic and evolved secondarily into pelagic predators, and (2) paedomorphosis has dominated mechanisms affecting their morphological change. Using cladistic methods, this study examines generic level interrelationships within Acipenseridae. Representatives of the four acipenserid genera Huso, Acipenser, Pseudoscaphirhynchus, and Scaphirhynchus, as well as their acipenseriform outgroups Polyodontidae, Peipiaosteidae, and Chondrosteidae, were surveyed for skeletal characters. Sixty-nine characters are identified and described to support the first generic level cladogram of Acipenseridae. Huso is phylogenetically primitive within Acipenseridae and the sister group to a redefined subfamily Acipenserinae. Acipenser is not supported by any characters identified in this study, but the tribe Scaphirhynchini comprising Scaphirhynchus and Pseudoscaphirhynchus is found to be monophyletic. The cladogram contradicts historical ideas about acipenserid evolution because Huso defines an outgroup morphology and life history founded on pelagic habitats and piscivory. In contrast, acipenserines, and more markedly scaphirhynchines, are benthic predators possessing character complexes for benthic feeding, respiration, locomotion, and protection. Also, the pattern of character acquisition within Acipenseridae suggests that peramorphosis played a central role in acipenserid evolution. Peramorphic addition and enlargement of the skeleton and scalation defines most characters at all nodes within Acipenseridae, and repudiates paedomorphosis as a major trend in evolution within the family Acipenseridae.