Species-specific Habitat Preferences Research Articles

Habitat partitioning among sympatric tinamous in semiarid woodlands of central Argentina.

Sympatric, phylogenetically related and morphologically similar species that overlap in their distributions at a regional scale display different patterns of co-occurrence at local assemblages. Occurrence of each species at local scales might be the result of interspecific competition for limiting resources. However, these patterns could also arise from species-specific habitat preferences along the abiotic or land use gradients. To assess the role of these mechanisms, we investigated niche partitioning among sympatric tinamou species occurring in semiarid woodlands of central Argentina. We used occupancy models incorporating habitat characteristics and interspecific interactions, while accounting for detectability, to examine the spatial overlap among elegant crested tinamous (Eudromia elegans), brushland tinamous (Nothoprocta cinerascens), and nothura tinamous (Nothura darwinii and N. maculosa) across a wide regional scale. In addition, we investigated time partitioning among these species by estimating the degree of overlap in their daily activity patterns. The regional distribution of the three species was influenced by the gradient in plant productivity and vegetation structure, in agreement with their broad habitat requirements. We also found that the occurrence of each species was presumably affected by the presence of one or two predator species. Models including interactions among tinamou species found weak negative and positive interactions among species pairs, suggesting that co-occurrence patterns were mainly driven by species-specific habitat use rather than interspecific competition. The three species were diurnal, showing two main peaks of activity, and overlapped widely in their overall diel activity, although subordinate species tended to shift their activity patterns to reduce encounters with the dominant tinamou species, suggesting some segregation in this niche dimension. Projected changes in rainfall seasonality and warmer conditions in this region could benefit elegant crested tinamous over the other two species, although climate and land use changes will likely have a negative impact on all tinamou species.

Taxonomy, Distribution and Habitat of the Giant Trechus Beetles Endemic to Mt. Choke, Ethiopia (Coleoptera: Carabidae)

The Holarctic ground beetle genus Trechus Clairville, 1806, is highly diverse in the Ethiopian highlands, both in terms of species numbers and morphology. Particularly noteworthy are the extraordinarily large species of the subgenus Abyssinotus Quéinnec and Ollivier, 2021, with a body length up to 8.5 mm, that occur on Mt. Choke in northern Ethiopia. Recent, intensive field work on Mt. Choke resulted in a significantly large number of specimens that are the basis for our taxonomic revision of the species related to the giant species, T. dimorphicus Pawłowski, 2001 and T. gigas Pawłowski, 2001. We describe three new species and one new subspecies and discuss a likely interspecific hybrid that combines morphological character states of representatives of the dimorphicus and gigas subgroups of Abyssinotus. An iconography of males and females as well as photographs of the aedeagi of all the considered species are presented. The distributions of the species are detailed and knowledge of the species-specific habitat preferences is summarized. Based on the distributions and habitat specificity, a threat assessment based on the current land use pattern at Mt. Choke is provided.

Developing a subseasonal ecological forecast to reduce fisheries bycatch in the Northeast U.S.

Over the past decade, substantial progress has been made in projecting and predicting the spatial distribution of many marine species at seasonal to multidecadal time scales. However, managers and fishers often need to make decisions at much shorter time scales. Subseasonal environmental forecasts, which generate predictions over one to several weeks, can now be combined with species-specific habitat preference data to create ecological forecasts that could facilitate dynamic spatial management. The development of such predictive tools could aid in identifying optimal times and areas for fishers to maximize target catch and avoid nontarget catch. Nontarget catch, or bycatch, can have numerous and potentially severe economic and ecological consequences. Here, we focus on a population of anadromous fish known collectively as river herring (alewife and blueback herring), as they are species of concern and are heavily impacted by bycatch. Using bottom trawl survey data from the Northeast US and subseasonal forecasts of sea surface temperature, we constructed a bycatch risk model to generate probabilistic predictions of river herring distributions in regions frequented by the US mid-water trawl fishery. Assessments of model skill showed that our ecological model performed well in predicting the distribution of river herring and that subseasonal forecasts were effective at 1-week timeframes. There was a clear seasonal effect on forecasted bycatch risk throughout the Northeast US, with particularly high risk in winter and spring months. Importantly, variability in risk was detectable at the weekly timescale and our model identified specific areas and times that fishers should avoid in order to decrease their likelihood of bycatch. The bycatch risk forecast developed in this study is a significant advance from near-real time forecasts and the foundation to build forecast systems by combining species co-occurrence models with subseasonal forecasts. As these subseasonal forecasts are available globally, this approach could be adapted to facilitate the management of other natural resource conflicts around the world.

Laboratory-based measures of temperature preference and metabolic thermal sensitivity provide insight into the habitat utilisation of juvenile California horn shark (Heterodontus francisci) and leopard shark (Triakis semifasciata).

Laboratory-based studies examining fish physiological and behavioural responses to temperature can provide important insight into species-specific habitat preferences and utilisation, and are especially useful in examining vulnerable life stages that are difficult to study in the wild. This study couples shuttle box behavioural experiments with respirometry trials to determine the temperature preferences and metabolic thermal sensitivity of juvenile California horn shark (Heterodontus francisci) and leopard shark (Triakis semifasciata). As juveniles, these two species often occupy similar estuarine habitats but display contrasting behaviours and activity levels - H. francisci are relatively sedentary, whereas T. semifasciata are more active and mobile. This study shows that juvenile H. francisci and T. semifasciata have comparable thermal preferences and occupy similar temperature ranges, but H. francisci metabolism is more sensitive to acute changes in temperature as expressed through a higher Q10 (H. francisci=2.58; T. semifasciata=1.97; temperature range: 12-24°C). Underlying chronic temperature acclimation to both warm (21°C) and cool (15°C) representative seasonal temperatures did not appear to significantly affect these parameters. These results are discussed in the context of field studies examining known distributions, habitat and movement patterns of H. francisci and T. semifasciata to better understand the role of temperature in species-specific behaviour. Juvenile H. francisci likely target thermally stable environments, such as estuaries that are close to their preferred temperature, whereas juvenile T. semifasciata metabolism and behaviour appear less dependent on temperature.

Investigating fishing strategies and habitat differences in late Holocene Oregon Coast sturgeon (Acipenser spp.) through coupled genetic and isotope analyses

Understanding the habitats people were fishing in the past is central to evaluating the relationship between coastal environmental change and human behavior. Researchers often use zooarchaeological identification of fishes and modern ecological data to infer the habitats people fished in the past. However, these inferences assume stable environmental conditions through time and can be hindered by precision issues in identification of archaeological specimens (species vs. genus or family). Here, we integrate genetic and bulk tissue stable isotope data to investigate a late Holocene sturgeon fishery in northern Oregon. Ancient DNA analysis indicated that people were fishing for both green and white sturgeon (Acipenser medirostris and Acipenser transmontanus) in comparable numbers. Stable isotope analyses of these same bones documented distinct isotope values for each species, correlating with species-specific habitat preferences. These findings highlight the value of paired isotope and genetic data to elucidate human fishing strategies and environmental change and provide baseline ecological data for modern fisheries.

Competitive release during fire succession influences ecological turnover in a small mammal community.

Ecologists have long debated the relative importance of biotic interactions versus species-specific habitat preferences in shaping patterns of ecological dominance. In western North America, cycles of fire disturbance are marked by transitions between North American deermice (Peromyscus maniculatus), which predominate after wildfires, and southern red-backed voles (Myodes gapperi), which gradually replace deermice 3-4 years postfire and maintain dominance as forests mature. While this shift has been frequently documented, the processes that mediate this turnover are debated. One possibility is competitive release, which predicts a reduction in vole competition may contribute to niche expansion and population growth in deermice. Alternatively, turnover in both species may be shaped by differences in their preferred habitat and resource base, as predicted by optimum foraging theory. We evaluate these hypotheses using stable isotopes and spatial mark-recapture of deermouse and vole populations sampled prior to and following a fire as part of a longitudinal study in the Greater Yellowstone Ecosystem. Fire disturbance was associated with a 94% decrease in vole abundance but a 102% increase in deermice. Even after accounting for microhabitat, vole and deermouse populations were negatively correlated spatially and temporally (R=-0.45), and competitor abundance was more important prefire than postfire. When vole abundance was high (prefire), vole dietary niche space was seven times broader than that of deermice. Postfire, deermouse dietary niche nearly tripled and was enriched in 13 C (i.e., more C4 plants), while voles occupied a slightly reduced dietary niche (79% of prefire breadth). Our results suggest deermice are experiencing ecological release due to a reduction in vole competition but vole shifts are largely driven by habitat preferences.

Successful parks for sharks: No-take marine reserve provides conservation benefits to endemic and threatened sharks off South Africa

Sharks are among the most threatened vertebrates on the planet. Marine protected areas (MPAs) have been widely established and promoted as a shark conservation tool. However, the geographic ranges of most imperiled shark species (endemic and threatened) fall outside the current global networks of MPAs, leaving the protective benefits of this tool questionable for the shark species of highest conservation concern. The Western Cape of South Africa is a hotspot for endemic and threatened shark species. Here, we examined the potential protective benefit of a no-take marine reserve (the De Hoop MPA) for imperiled shark species using baited remote underwater video stations (BRUVS). Eleven shark species were documented, with six of 11 species (55%) classified as threatened with extinction by the International Union for the Conservation of Nature. The composition of the shark assemblage was dominated by small to mid-sized species, including small endemics. Species-specific habitat preferences were identified, with all these habitats represented in the MPA. Frequency of occurrence and relative abundance of sharks on BRUVS were significantly higher inside the De Hoop MPA than outside. Both protected and commercially exploited sharks species exhibited higher relative abundance inside the MPA. Relative abundance also increased inside the MPA with increasing distance from the reserve boundaries. Our findings suggest that no-take MPAs can be an effective tool for protecting shark species of conservation concern, including threatened endemics, particularly if the MPA adequately incorporates their preferred habitats.

Habitat Use of Constant Frequency Echolocating Bats in North-West Madagascar with Acoustic Evidence for a Possible New Species

Bioacoustics can be a non-invasive, cost-effective way of studying echolocating bats, and is especially useful for detecting and identifying rare or cryptic species. The insectivorous bats of Madagascar are understudied in comparison to the rest of the island's fauna, and very little is known about their habitat use. Here, we used a remote bioacoustic surveying technique in a bat survey of the Sahamalaza-Îles Radama National Park, northwest Madagascar, to study constant frequency echolocating bats (Hipposideridae and Rhinonycteridae). We used two passive acoustic monitoring units to automatically record bat activity from dusk until dawn in a range of habitat types that are characteristic of the region. Analysis of call acoustic parameters revealed three distinct constant-frequency phonic types within the national park, which we identified as Commerson's leaf-nosed bat (Macronycteris commersoni), the red trident bat (Triaenops menamena) and an unknown phonic type of ca. 78 kHz. We found significant differences in the habitat usage of these three species, suggesting species-specific habitat preferences among Madagascar's bats. Our statistical analyses revealed significant differences between the acoustic echolocation calls of these three phonic types. The 78 kHz calls do not match any of the other constant frequency-calling bat species currently described for Madagascar, indicating either acoustic divergence among bat sub-populations or the possible existence of a new undescribed species. These results highlight the need for increased survey efforts to gain an understanding of species-specific geographic distributions and habitat usage among Malagasy bats and to disentangle their cryptic species complexes.

Topography shapes the local coexistence of tree species within species complexes of Neotropical forests.

Forest inventories in Amazonia include around 5000 described tree species belonging to more than 800 genera. Numerous species-rich genera share genetic variation among species because of recent speciation and/or recurrent hybridisation, forming species complexes. Despite the key role that tree species complexes play in understanding Neotropical diversification, and their need to exploit a diversity of niches, little is known about the mechanisms that allow local coexistence of tree species complexes and their species in sympatry. In this study, we explored the fine-scale distribution of five tree species complexes and 22 species within these complexes. Combining forest inventories, botanical determination, and LiDAR-derived topographic data over 120ha of permanent plots in French Guiana, we used a Bayesian modelling framework to test the role of fine-scale topographic wetness and tree neighbourhood on the occurrence of species complexes and the relative distribution of species within complexes. Species complexes of Neotropical trees were widely spread across the topographic wetness gradient at the local scale. Species within complexes showed pervasive niche differentiation along with topographic wetness and competition gradients. Similar patterns of species-specific habitat preferences were observed within several species complexes: species more tolerant to competition for resources grow in drier and less fertile plateaus and slopes. If supported by partial reproductive isolation of species and adaptive introgression at the species complex level, our results suggest that both species-specific habitat specialisation within species complexes and the broad ecological distribution of species complexes might explain the success of these species complexes at the regional scale.

Proactive conservation to prevent habitat losses to agricultural expansion

The projected loss of millions of square kilometres of natural ecosystems to meet future demand for food, animal feed, fibre and bioenergy crops is likely to massively escalate threats to biodiversity. Reducing these threats requires a detailed knowledge of how and where they are likely to be most severe. We developed a geographically explicit model of future agricultural land clearance based on observed historical changes, and combined the outputs with species-specific habitat preferences for 19,859 species of terrestrial vertebrates. We project that 87.7% of these species will lose habitat to agricultural expansion by 2050, with 1,280 species projected to lose ≥25% of their habitat. Proactive policies targeting how, where, and what food is produced could reduce these threats, with a combination of approaches potentially preventing almost all these losses while contributing to healthier human diets. As international biodiversity targets are set to be updated in 2021, these results highlight the importance of proactive efforts to safeguard biodiversity by reducing demand for agricultural land. Agricultural expansion to grow food, fibre and biofuel will further threaten biodiversity. This study finds that almost 90% of terrestrial vertebrate species will lose habitat to such expansion, but proactive food policies could reduce these threats.

Resource partitioning among avian predators of the Arctic tundra.

Interspecific competition can play a key role in structuring ecological communities. The Arctic tundra is a low productivity ecosystem supporting simple food webs, but several predators often feed on the same prey species, lemmings, known for their large-amplitude population fluctuations. We examined mechanisms involved in reducing intra-guild competition and allowing coexistence of four avian predators (snowy owls, glaucous gulls, rough-legged hawks and long-tailed jaegers) feeding on a pulsed resource (brown and collared lemmings). We compared the size and species of prey consumed by predators to see if resource partitioning occurred. We also verified if spatial segregation in nesting areas could be another mechanism allowing coexistence. Finally, we tested if the absence of the snowy owl, a dominant and irruptive species, triggered a competitive release on the smallest predator, the jaeger, with respect to prey size and nesting area used. We monitored the breeding of predators and lemming abundance over a 14-year period on Bylot Island, Canada. We mapped their nesting sites and collected regurgitation pellets to recover lemming mandibles, which were used to infer prey species and size. The size of lemmings consumed varied among species with the largest predators consuming the largest lemmings and the smallest predators consuming the smallest lemmings. All predators consumed more collared than brown lemmings compared to their availability although owls and jaegers consumed relatively more brown lemmings compared to gulls and hawks. Jaegers consumed larger lemmings in the absence of owls than in their presence, suggestive of a short-term competitive release. We found moderate to low overlap in nesting areas among predators and no evidence of their expansion in the absence of owls, suggesting that spatial distribution is caused by species-specific habitat preferences. The main mechanism to partition food resources among these avian predators is spatial segregation, and secondarily prey size and species. However, we found evidence that food competition is still present and leads to a niche shift in the smallest predator of the guild. Interspecific competition may thus be a pervasive force in simple, low productivity food webs characterized by pulsed resources.

Exploring the potential of metabarcoding to disentangle macroinvertebrate community dynamics in intermittent streams

Taxonomic sufficiency represents the level of taxonomic detail needed to detect ecological patterns to a level that match the requirement of a study. Most bioassessments apply the taxonomic sufficiency concept and assign specimens to the family or genus level given time constraints and the difficulty to correctly identify species. This holds particularly true for stream invertebrates because small and morphologically similar larvae are hard to distinguish. Low taxonomic resolution may hinder detecting true community dynamics, which thus leads to incorrect inferences about community assembly processes. DNA metabarcoding is a new, affordable and cost-effective tool for the identification of multiple species from bulk samples of organisms. As it provides high taxonomic resolution, it can be used to compare results obtained from different identification levels. Measuring the effect of taxonomic resolution on the detection of community dynamics is especially interesting in extreme ecosystems like intermittent streams to test if species at intermittent sites are subsets of those from perennial sources or if independently recruiting taxa exist. Here we aimed to compare the performance of morphological identification and metabarcoding to detect macroinvertebrate community dynamics in the Trebbia River (Italy). Macroinvertebrates were collected from four perennial and two intermittent sites two months after flow resumption and before the next dry phase. The identification level ranged from family to haplotype. Metabarcoding and morphological identifications found similar alpha diversity patterns when looking at family and mixed taxonomic levels. Increasing taxonomic resolution with metabarcoding revealed a strong partitioning of beta diversity in nestedness and turnover components. At flow resumption, beta diversity at intermittent sites was dominated by nestedness when family-level information was employed, while turnover was evidenced as the most important component when using Operational Taxonomic Units (OTUs) or haplotypes. The increased taxonomic resolution with metabarcoding allowed us to detect species adapted to deal with intermittency, like the chironomidCricotopus bicinctusand the ephemeropteranCloeon dipterum. Our study thus shows that family and mixed taxonomic level are not sufficient to detect all aspects of macroinvertebrate community dynamics. High taxonomic resolution is especially important for intermittent streams where accurate information about species-specific habitat preference is needed to interpret diversity patterns induced by drying and the nestedness/turnover components of beta diversity are of interest to understand community assembly processes.

The Influence of Forests on Freshwater Fish in the Tropics: A Systematic Review.

Tropical forests influence freshwater fish through multiple pathways, only some of which are well documented. We systematically reviewed the literature to assess the current state of knowledge on forests and freshwater fish in the tropics. The existing evidence is mostly concentrated in the neotropics. The majority of studies provided evidence that fish diversity was higher where there was more forest cover; this was related to the greater heterogeneity of resources in forested environments that could support a wider range of species. Studies quantifying fish abundance (or biomass) showed mixed relationships with forest cover, depending on species-specific habitat preferences. We identify the key challenges limiting our current understanding of the forest–fish nexus and provide recommendations for future research to address these knowledge gaps. A clear understanding of the functional pathways in forest–freshwater ecosystems can improve evidence-based policy development concerned with deforestation, biodiversity conservation, and food insecurity in the tropics.

Combined effects of land use and hunting on distributions of tropical mammals

Land use and hunting are 2 major pressures on biodiversity in the tropics. Yet, their combined impacts have not been systematically quantified at a large scale. We estimated the effects of both pressures on the distributions of 1884 tropical mammal species by integrating species’ range maps, detailed land‐use maps (1992 and 2015), species‐specific habitat preference data, and a hunting pressure model. We further identified areas where the combined impacts were greatest (hotspots) and least (coolspots) to determine priority areas for mitigation or prevention of the pressures. Land use was the main driver of reduced distribution of all mammal species considered. Yet, hunting pressure caused additional reductions in large‐bodied species’ distributions. Together, land use and hunting reduced distributions of species by 41% (SD 30) on average (year 2015). Overlap between impacts was only 2% on average. Land use contributed more to the loss of distribution (39% on average) than hunting (4% on average). However, hunting reduced the distribution of large mammals by 29% on average; hence, large mammals lost a disproportional amount of area due to the combination of both pressures. Gran Chaco, the Atlantic Forest, and Thailand had high levels of impact across the species (hotspots of area loss). In contrast, the Amazon and Congo Basins, the Guianas, and Borneo had relatively low levels of impact (coolspots of area loss). Overall, hunting pressure and human land use increased from 1992 to 2015 and corresponding losses in distribution increased from 38% to 41% on average across the species. To effectively protect tropical mammals, conservation policies should address both pressures simultaneously because their effects are highly complementary. Our spatially detailed and species‐specific results may support future national and global conservation agendas, including the design of post‐2020 protected area targets and strategies.

The effect of ground surface rugosity on ant running speed is species-specific rather than size dependent

Foraging is one of the main reasons for ants to walk. Foraging speed is mainly dependent on morphological traits, but also on the surface structure. The size-grain hypothesis (SGH) suggests that (1) relative leg length should increase allometrically with body size, and (2) smaller, shorter legged species have an advantage with increasing habitat complexity in comparison to larger and longer legged species. In general, it is thought that leg length is a good predictor for running speed. We performed morphological analyses and running experiments with differently sized ant species along an artificial gradient of surface rugosity. We measured running speed, number of steps, body size and leg length to answer the question, if morphological traits can be used to predict the running speed of ants in complex habitats, as predicted by the SGH. We found that (1) leg length increased allometrically with body size, and that (2) the largest species were among the fastest and could sustain their speed with increasing surface rugosity. The smallest species with the relatively shortest legs were the fastest on the flattest surface, but their speed decreased rapidly with increasing rugosity. Leg length was not a good predictor for running speed. Similar-sized species responded idiosyncratically to high surface rugosity, which might be related to species-specific habitat preferences. Species-specific behavior or stride frequency influenced running speed strongly, which hampers precise predictions on their running speed, based on morphological traits exclusively.

Winter bird communities in the heterogeneous farmlands of the Aso region in Japan

Surveys of overwintering birds were conducted in a heterogeneous landscape, composed of paddy land, grassland, and mosaic agricultural land types, in the Aso region of Japan. Overall species richness and mean abundance were higher in paddy land types compared with the other two land types. Birds showed species-specific habitat preferences, with 26 species (56.5%) only being found on one of the three farmland types. Using canonical correspondence analysis, wider-ranging species were separated to species preferring forest and shrub vegetation sites compared with paddy field–dominated sites along the first axis. The environmental factors that explained individual abundance by generalized linear mixed models also differed among species and were dependent on the degree of paddy field, grass, shrub, and broad spatial forest cover. The most frequently detected bird species, Hypsipetes amaurotis, was positively correlated with the percentage of forests in paddy fields and grasslands at the local scale, where forests were rare. In conclusion, paddy lands that extend into valleys represent important habitat promoting high bird diversity during the wintering period, with the other two land types also supporting many species in this region at the landscape level.

Inferring abundance trends of key species from a highly developed small-scale fishery off NE Atlantic

Small-scale fisheries (SSFs) are large contributors to worldwide catches and local economies; however, SSFs have been historically under-attended in national and international policies. This work presents a standardization of catch-per-unit-of-effort data obtained from onboard observers for twenty commercial coastal species caught by the SSFs off the Galician coast from 2000 to 2016 using generalized linear mixed models. Operational, environmental, temporal and spatial data were included in the models as explanatory variables. The relative index of abundance for most species varied from year-to-year over the study period and between geographical areas (ICES 9.a and 8.c). Seasonal patterns, likely related to annual biological cycles, were found. Vessel size showed restricted significant effects in abundance estimates, and soak time of fishing operations revealed nonlinear responses of catch rates. Fishing at night or during daylight hours also have significant differences in catch rates that varied among species pointing to behavioural effects on catchability. Catch rates were often negatively related with depth as expected for species with a coastal distribution. Furthermore, seafloor type indicated species-specific habitat preferences, and sea surface temperature played a limited role in abundance estimations. The most common trend of species’ abundance indices showed opposite patterns among geographical areas, suggesting that local conditions may have a significant influence on fluctuations not only at the species level, but also at the community level. This study revealed a generalized lack of correlation between landings and abundance indices, thus landing data was considered, in general, a poor indicator of population status. The data presented increase the fishery knowledge of one of the most important European SSF fleets that ultimately would allow implementing future assessment strategies. It also underpins the fact that fine scale spatial, and temporal observer data, together with environmental and operational information, are critical to infer suitable and unbiased abundance indices within a complex SSF context.

Ontogenetic milestones of chemotactic behaviour reflect innate species-specific response to habitat cues in larval fish

The distribution and connectivity of marine populations are largely dependent on biophysical factors affecting pelagic larval dispersal between spawning at adult spawning sites and settlement to juvenile nursery habitats. Behaviour and swimming ability of pelagic larvae are increasingly understood to influence patterns of dispersal, but it is unclear which sensory cues are involved and when during ontogeny these abilities first develop. Here we studied the early ontogenetic development of responses to olfactory cues from coastal and estuarine waters in larvae of two temperate estuarine-associated fish species, Australian bass, Macquaria novemaculeata, and mulloway, Argyrosomus japonicus, to determine when olfaction begins to influence dispersal. Olfactory responses to habitat-associated cues were not present when larvae first transitioned from nonswimming to swimming (indicated by flexion of the notochord), but emerged after ca. 7 days in a species-specific manner that was consistent across different cohorts. Based on general additive models (GAMs), age (in days posthatch) best explained the ontogenetic pattern in both species. The emergence of chemotactic responses coincides with an exponential increase in swimming endurance reported for these species. This suggests the existence of ontogenetic milestones during larval development that, once reached, trigger active influence on dispersal. Salinity and pH did not influence choice behaviour after these ontogenetic milestones; however, the presence of cues generated by seagrass harvested from the estuary habitat elicited strong responses in fish larvae consistent with species-specific habitat preferences, indicating an important role for aquatic vegetation in driving these behaviours.

Species distribution models of two critically endangered deep-sea octocorals reveal fishing impacts on vulnerable marine ecosystems in central Mediterranean Sea

Deep-sea coral assemblages are key components of marine ecosystems that generate habitats for fish and invertebrate communities and act as marine biodiversity hot spots. Because of their life history traits, deep-sea corals are highly vulnerable to human impacts such as fishing. They are an indicator of vulnerable marine ecosystems (VMEs), therefore their conservation is essential to preserve marine biodiversity. In the Mediterranean Sea deep-sea coral habitats are associated with commercially important crustaceans, consequently their abundance has dramatically declined due to the effects of trawling. Marine spatial planning is required to ensure that the conservation of these habitats is achieved. Species distribution models were used to investigate the distribution of two critically endangered octocorals (Funiculina quadrangularis and Isidella elongata) in the central Mediterranean as a function of environmental and fisheries variables. Results show that both species exhibit species-specific habitat preferences and spatial patterns in response to environmental variables, but the impact of trawling on their distribution differed. In particular F. quadrangularis can overlap with fishing activities, whereas I. elongata occurs exclusively where fishing is low or absent. This study represents the first attempt to identify key areas for the protection of soft and compact mud VMEs in the central Mediterranean Sea.

Abundance and habitat associations of tuna larvae in the surface water of the Gulf of Mexico

Summer ichthyoplankton surveys were conducted in the northern Gulf of Mexico from 2007 to 2010 to characterize the distribution and abundance of tuna larvae. Larval assemblages of tunas were comprised of four genera: Thunnus, Auxis, Euthynnus, and Katsuwonus. Thunnus were the most abundant and four species were detected; T. atlanticus [blackfin tuna], T. obesus [bigeye tuna], T. albacares [yellowfin tuna], and T. thynnus [bluefin tuna]. Intra- and inter-annual variability in the distribution and abundance of Thunnus species were observed with higher densities in 2008 and 2009, with a decline in abundance observed in 2010. Distribution and abundance of Thunnus larvae were influenced by physical and chemical conditions of the water mass, notably sea surface temperature and salinity. Distinct species-specific habitat preferences were observed and the location of mesoscale oceanographic features influenced larval abundance with higher densities of T. atlanticus, T. obesus, and T. albacares near anticyclonic (warm core) regions and the Loop Current, while T. thynnus was observed in higher densities near cyclonic (cold core) regions. This study demonstrates that spatial and temporal variability in the location of mesoscale oceanographic features may be important to partitioning nursery habitat among Thunnus species.