Shipping traffic, salinity and temperature shape non-native fish richness in estuaries worldwide

Non-native species threaten biodiversity conservation and ecosystem functioning. Management at early-invasion stages can prevent ecological and socioeconomic impacts, but rely on the identification of drivers of non-native species occurrence at distinct scales. Here, we identify environmental and anthropogenic correlates of non-native fish richness across estuaries worldwide. We performed model selection using proxies of colonization pressure, habitat availability and connectivity, anthropogenic disturbance and climate, to assess the primary mechanisms underlying non-native species occurrence. Latitudinal and guild-related trends in non-native occurrence were also investigated using species thermal and salinity affinities. Data retrieved from a literature review revealed 147 non-native fish species in 147 estuaries worldwide. Shipping traffic, salinity (minimum and range values) and temperature (minimum value) were the main predictors of non-native fish richness. Hotspots of non-native species were under heavy levels of shipping traffic, had higher salinity (both minimum and range values) and colder waters. We also found evidence of thermal limits to species' geographic area of introduction. Latitude of invaded estuaries was negatively correlated with species' minimum, mean and maximum thermal affinities, and positively correlated with thermal affinity ranges. Most non-native species recorded in estuaries were freshwater, but their minimum salinity affinities ranged from 2 to 35 pss. Moreover, species within marine guilds were mostly stenohaline and showed affinity for minimum salinities around 20-30 pss, which may be related to the positive relationship between non-native richness and estuary's increased salinity. Our results indicate that colonization pressure, disturbance (as result of multiple shipping impacts) and habitat filtering are the primary mechanisms underlying non-native fish richness in estuaries, contributing to the development of management strategies targeting early-invasion stages. Matching climate between native and non-native ranges was particularly important for predicting introductions at the global scale, whereas local fluctuations in salinity likely drove non-native richness in response to increased habitat availability.

Habitat-use of the vulnerable Atlantic Nurse Shark: a review

Human activities have led to the loss of critical habitats for aquatic species at such an accelerated rate that habitat modification is considered a leading threat to biodiversity. Sharks and rays are considered the second most threatened group of vertebrates that have also suffered from habitat loss, especially in nursery grounds and reef-associated species. In this sense, actions toward the conservation of critical grounds for species survival are urgently needed, especially for those threatened with extinction. This study aimed to gather and provide information on the worldwide distribution and habitat association of the 'vulnerable' Atlantic Nurse Shark Ginglymostoma cirratum through a literature review performed at the Dimensions research database. A total of 30 studies published between 1950 and 2021 were retained since they defined at least the type of habitat in which G. cirratum was associated. Most studies covered the Floridian ecoregion, where G. cirratum is more common and abundant. Reefs, seagrass, sandy, rocky, mangrove, and macroalgae accounted for the majority of habitat associations, with a higher diversity of habitats detected within marine protected areas (MPAs). Ginglymostoma cirratum was recorded at a maximum depth of 75 m, temperatures ranging from 25 °C to 34 °C, and salinities between 31 and 38 ppt. Neonates were associated with shallower habitats (<20 m), mostly reefs, rocks, macroalgae, sandy shores, and seagrass, in an average temperature of 26 °C and salinity of 36 ppt. Breeding events and habitats were reported by 11 studies, 72.7% of them in shallow waters, mostly inside MPAs (90.9%). Our findings highlighted the key role played by MPAs in protecting essential grounds for threatened species, such as the Atlantic Nurse Shark. Major ecoregions (e.g., the Eastern Atlantic) are still underrepresented in the scientific literature as long as studies aim specifically to assess G. cirratum habitat association. Thus, further insights into the essential habitats needed to conserve the Atlantic Nurse Shark can still emerge from future studies. Considering the recent IUCN extinction risk status change in G. cirratum (i.e., Data Deficient to 'Vulnerable'), new conservation measures that integrate habitat protection and management are urgently needed and should consider the data collected herein.

NEOTROPICAL FRESHWATER FISHES: A dataset of occurrence and abundance of freshwater fishes in the Neotropics

The Neotropical region hosts 4225 freshwater fish species, ranking first among the world's most diverse regions for freshwater fishes. Our NEOTROPICAL FRESHWATER FISHES data set is the first to produce a large-scale Neotropical freshwater fish inventory, covering the entire Neotropical region from Mexico and the Caribbean in the north to the southern limits in Argentina, Paraguay, Chile, and Uruguay. We compiled 185,787 distribution records, with unique georeferenced coordinates, for the 4225 species, represented by occurrence and abundance data. The number of species for the most numerous orders are as follows: Characiformes (1289), Siluriformes (1384), Cichliformes (354), Cyprinodontiformes (245), and Gymnotiformes (135). The most recorded species was the characid Astyanax fasciatus (4696 records). We registered 116,802 distribution records for native species, compared to 1802 distribution records for nonnative species. The main aim of the NEOTROPICAL FRESHWATER FISHES data set was to make these occurrence and abundance data accessible for international researchers to develop ecological and macroecological studies, from local to regional scales, with focal fish species, families, or orders. We anticipate that the NEOTROPICAL FRESHWATER FISHES data set will be valuable for studies on a wide range of ecological processes, such as trophic cascades, fishery pressure, the effects of habitat loss and fragmentation, and the impacts of species invasion and climate change. There are no copyright restrictions on the data, and please cite this data paper when using the data in publications.

Ecological impacts of an invasive top predator fish across South America

Peacock bass Cichla ocellaris is a piscivorous cichlid native from the Amazon and Orinoco river basins, which has been broadly introduced into tropical areas worldwide, leading to several adverse local effects. However, predictors of its invasibility and assessments of its ecological impacts over large spatial scales are still lacking. The importance of different environmental factors in explaining the relative abundance of peacock bass in 62 sites across South America (30 native and 32 invaded systems) was investigated. The impacts of peacock bass on fish assemblages were appraised, using years since introduction as a proxy of its cumulative impacts and modern statistical techniques, such as random forests, and negative binomial regression models. Random forests highlighted maximum depth, introduced status, and ecosystem type as the best predictors of the peacock bass relative abundance, which ranged 0.01-26.0%, increased with maximum depth, was highest in invaded reservoirs but decreased with depth in native riverine populations. Other factors such as climate or limnological features were less important in explaining C. ocellaris abundance, which did not vary markedly with years since introduction. Introduction year was not related to latitude but varied among hydrographic regions, indicating invasion pathways not linked to geographical proximity. Variation partitioning of different fish assemblage metrics showed that hydrographic region followed by limnological and reservoir features accounted for most explained variation, indicating a strong historical and local influence. Introduction time accounted for 5-8% of variation in species composition and diversity, independently of limnological features. Our results suggest that the ecological effects of introduced C. ocellaris on native fish fauna are likely but small compared to large geographical and environmental gradients. Although experiments and before-after designs are probably more sensitive in detecting the ecological impacts of invasive species, large-scale compilations of available data are more feasible and can provide invaluable information, especially for large-sized invaders that are often illegally introduced.

Genetic divergence among invasive and native populations of the yellow peacock cichlid Cichla kelberi

This study used the hypervariable domain of the mitochondrial DNA (mtDNA) control region (CR) to assess the genetic divergence among native and invasive populations of Cichla kelberi, which is considered the first peacock cichlid introduced and established throughout Brazil and is among the most invasive populations of this genus worldwide. The maximum likelihood tree based on 53 CR sequences with strong bootstrap support revealed that C. kelberi forms a monophyletic clade, confirming that all 30 C. kelberi studied belong to this morphotype. Additionally, the haplotype analysis of the C. kelberi sequences from 11 sampling sites revealed that invasive populations are much less diverse than native ones and largely dominated by a single haplotype that prevailed in reservoirs at the Paraíba do Sul River basin. Two haplotypes were recorded exclusively in an invasive population at Porto Rico, southern Brazil, and one private haplotype was detected in two reservoirs from Paraíba do Sul (Pereira Passos and Paracambi), suggesting more than one introduction event and that native populations should be better evaluated to encompass the entire genetic diversity of native C. kelberi. The possible route and pathways of C. kelberi introduction are also briefly discussed.

Responses of fish assemblages of sandy beaches to different anthropogenic and hydrodynamic influences

This study tested whether some attributes of the diversity, communities and populations of surf-zone fish assemblages varied with different hydrodynamic and anthropogenic influences at four Guanabara Bay sandy beaches: Dentro (sheltered with limited human access), Fora (exposed with limited human access), Urca (sheltered with unlimited human access) and Vermelha (exposed with unlimited human access), between autumn 2011 and summer 2012. Twenty-nine species and 1613 individuals were recorded from 76 trawls. The 10 most abundant species accounted for 94·5% of the total number, but only four species (Diplodus argenteus, Harengula clupeola, Sardinella brasiliensis and Sphoeroides greeleyi) were recorded at all four beaches, revealing a high level of species substitution. Fish assemblages differed not only for diversity attributes, but also at community and population levels, with lower values of the Shannon-Wiener index, richness and total fish abundance and biomass at Vermelha beach, and higher densities of Trachinotus carolinus, Atherinella brasiliensis and S. greeleyi related to beaches with high anthropogenic influence. The findings reveal that fish assemblages of Dentro, Fora, Urca and Vermelha beaches differed not only in response to hydrodynamic influences, but also due to the effects of different degrees of human interference (i.e. presence of solid residues, population density and fishing impacts), emphasizing the importance of the sheltered and less anthropogenically affected beaches, as spawning, nursery and growth areas.

Long-term (2002-2011) changes on Cetengraulis edentulus (Clupeiformes: Engraulidae) fisheries in Guanabara Bay, Brazil

C. edentulus accounts for the major fishery resource in Guanabara Bay, but there are only few studies about its captures.This study analyzed the long term changes on C. edentulus catches in Guanabara Bay, focusing especially on temporal variation on capture effort, boat storage temperature, and fish price and size.We assessed the 2002-2011 database of fish landings at the pier of Rubi S.A., with records of year, month, total catch (kg), number of fish per kg, boat storage temperature (OC), and price per kg to boat owner (US$). Those variables differed among years and months (ANOVA; p<0.01) with strong yearXmonth interactions for all, probably related to C. edentulus reproductive and recruitment seasons and environmental conditions of Guanabara Bay. Generalized additive models revealed that high C. edenuldus catches were associated with few boat loadings of large-sized fishes, which were conserved in higher boat storage temperatures and attained high market prices. Our long-term study stressed that variations on C. edentulus fishery were related to changes on boat storage temperature, fish size, price paid per kg, and frequency of landings, and that these descriptors are correlated with C. edentulus ecological traits and high phytoplankton availability. Nevertheless, further studies should be performed to address whether less evident factors, such as the fluctuation of concurrent Sardinella brasiliensis stock, would explain the termporal dynamics of C. edentulous stocks in Guanabara Bay.