Trophic overlap of lionfish (Pterois volitans) and two native predators (Lutjanus apodus and Cephalopholis cruentata) in the western Caribbean

Impact of invasive species on native biota may be due to predation, competition for space or food, or indirect effects. Lionfish (Pterois volitans), invasive in the western Atlantic, is a voracious generalist predator, so it is expected to have a significant trophic overlap with native fishes of comparable size and habits. The goal of this study was to determine the diets of potential competitors of the lionfish, in particular a grouper, Cephalopholis cruentata (Graysby), and a snapper, Lutjanus apodus (Schoolmaster), and to compare them to the diet of lionfish in Xcalak, southern Mexican Caribbean. Stomach contents were analyzed and electivity and diet overlap were estimated. The trophic overlap between the lionfish and the two putative competitors, especially the grouper, was high, including prey that was consumed by the predators in higher proportion than the relative abundance of the prey in the environment, and probably at the same time of day. Lionfish and grouper shared as important diet items Stegastes sp., Halichoeres sp., Brachyura, and Palaemonidae, and most full stomachs were found during the early morning. The hypothesis of competition between them for particular prey is supported, so we advise to continue the culling programs of lionfish and also to monitor the abundance of the possible native competitors.

Comparative cleaning behaviour of Pederson's cleaner shrimp (Ancylomenes pedersoni) between geographically close yet ecologically dissimilar coral reef habitats

Cleaning mutualisms are important interactions on coral reefs. Intraspecific variation in cleaning rate and behaviour occurs geographically and is often attributed to local processes. However, our understanding of fine-scale variation is limited, but would allow us to control for geography and region-specific behavioural patterns. Here, we compare the cleaning activity of Pederson's cleaner shrimp (Ancylomenes pedersoni) on two neighbouring, yet ecologically dissimilar, reef systems in Honduras: Banco Capiro, an offshore bank close to significant land runoff with high coral cover but a depleted fish population, and an oligotrophic fringing reef around the island of Utila, with lower coral cover but high fish abundance and diversity. The proportion of realized to potential fish clientele was <60% at both sites, and the composition of clientele was neither reflective of the demographics of the resident assemblages at each site nor similar between sites. Parrotfishes represented 13–15% of total fish abundance at both sites yet accounted for >50% (Banco Capiro) and 10% (Utila) of all cleans. Conversely, the schoolmaster snapper (Lutjanus apodus) represented ~1% of total fish abundance at both sites yet accounted for 40% (Utila) and 1% (Banco Capiro) of all cleans. After standardizing our cleaning rate data by clientele abundance, we find that clientele at Banco Capiro engage in over four times as many cleaning encounters per hour with A. pedersoni than at Utila. Our study highlights the variable nature of coral reef cleaning interactions and the need to better understand the ecological and environmental drivers of this biogeographic variation.

Fish Hybridization Leads to Uncertainty Regarding Ciguatera Fish Poisoning Risk; Confirmation of Hybridization and Ciguatoxin Accumulation with Implications for Stakeholders

Globally, ciguatera fish poisoning (CFP) avoidance efforts rely primarily on local knowledge of the fish being consumed, its collection location, and association with illnesses. In 2016, several fish that appeared to be hybrids between a local commercially prized species, Ocyurus chrysurus, and a regionally prohibited species Lutjanus apodus (due to CFP concerns), were caught nearshore in United States Virgin Islands waters, leading to confusion regarding the safety of consuming the fish. The hybrid status of the fish was verified as O. chrysurus (male) × L. apodus (female) by comparing two sets of gene sequences (mitochondrial CO1 and nuclear S7). Using an in vitro mouse neuroblastoma (N2a) assay, one of the hybrid fish exhibited a composite cytotoxicity of 0.038 ppb Caribbean ciguatoxin-1 (C-CTX-1) equivalents (Eq.); a concentration below the US Food and Drug Administration (FDA) guidance level for safety in fish products for CFP (0.1 ppb C-CTX-1 Eq.) but approximately 2× above the maximum described in the commercially prized parent species (0.019 ppb C-CTX-1 Eq./g). C-CTX-1 was confirmed in the hybrid sample by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The second hybrid fish tested negative for CTXs. This research confirms hybridization between two species with contrasting commercial statuses, discusses CTX accumulation implications for hybridization, and provides a methodology for future studies into novel CFP vectors, with the goal of providing critical information for fishermen and consumers regarding CFP risk management.

Age, growth, and natural mortality of schoolmaster (Lutjanus apodus) from the southeastern United States

Ages of schoolmaster (n= 136) from the southeastern Florida coast from 1981–2015 were determined using sectioned sagittal otoliths. Opaque zones were annular, forming March–July (peaking in May–June). Schoolmaster ranged in age from 1–42 years; the largest fish measured 505 mm total length (TL) and was 19 years old. The oldest fish measured 440 mm TL. Estimated body size relationships for schoolmaster were:W= 9.26 × 10−6TL3.11(n= 256,r2= 0.95);W= 2.13 × 10−5FL2.99(n= 161,r2= 0.95);TL= 1.03FL+ 10.36 (n= 143,r2= 0.99); andFL= 0.96TL− 8.41 (n= 143,r2= 0.99), whereW= whole weight in g,FL= fork length in mm, and TL in mm. The fitted von Bertalanffy growth equation was:Lt= 482 (1 −e−0.12(t+2.79)) (n= 136). Based on published life history relationships, a point estimate of natural mortality for schoolmaster wasM= 0.10, while age-specific estimates ofMranged from 1.57–0.18 for ages 1–42.

Distribution of estuarine fish fauna along coast of Brazil

O presente estudo teve como objetivos: listar a ictiofauna estuarina que ocorre no Brasil, a partir de dados compilados de artigos publicados em periódicos e em livros; rever a nomenclatura taxonômica válida das espécies; além de analisar ecologicamente as similaridades entre os segmentos ictiofaunísticos. Foram compilados os dados de 52 artigos científicos e livros, que tratam sobre assembleias de peixes estuarinos ou listas com abundância por espécie. Os trabalhos registraram 451 espécies válidas, sendo 225 associadas aos ambientes recifais, e 64 exclusivamente dulciaquícolas. Quatro espécies: Lutjanus apodus, L. griseus, Scartella nuchifilis e Scomberomorus maculatus não ocorrem na costa brasileira. Dentre as 104 famílias registradas, Sciaenidae foi predominante em todos os segmentos, exceto no V e no VIII. A análise de agrupamento indicou uma maior similaridade entre os segmentos II e III, e entre os segmentos V e VII. Palavras chave: Estuários, Peixes recifais, Similaridade.