Phylogeography of two marine predators, giant trevally (Caranx ignobilis) and bluefin trevally (Caranx melampygus), across the Indo-Pacific

For economically valuable marine fishes, identifying biogeographic barriers and estimating the extent of gene flow are critical components of fisheries management. We examined the population genetic structure of two commercially important reef-associated predators, the giant trevally ( Caranx ignobilis) and bluefin trevally (Caranx melampygus). We sampled 225 individuals and 32,798 single nucleotide polymorphisms (SNPs) of C. ignobilis, and 74 individuals and 43,299 SNPs of C. melampygus. Analyses of geographic population structure indicate the two species display subtly different phylogeographic patterns. Caranx ignobilis comprises two to three putative populations—one in the Central Pacific, one inhabiting the Western Pacific and Eastern Indian oceans, and one in the Western Indian Ocean—with some restricted gene flow between them. Caranx melampygus shows evidence of restricted gene flow from Hawaii to the West Pacific and Indian oceans, as well as limited genetic connectivity across the Indo- Pacific Barrier. Both species exhibit patterns characteristic of other large, reef-associated predators such as deepwater snappers and the great barracuda. This study contributes to ongoing assessments of the role of the Indo-Pacific Barrier in shaping patterns of phylogeography for large reef-associated fishes. Furthermore, by identifying putative populations of C. ignobilis and C. melampygus in the Central Pacific, our findings serve to improve future management measures for these economically important, data-limited species, particularly in light of historic and contemporary overfishing in Hawaii.

Crown-of-thorns starfish outbreak at Taiping Island (Itu Aba), Spratlys, South China Sea

Outbreak of crown-of-thorns sea stars, Acanthaster cf. solaris, were documented in coral reefs around Taiping Island, Spratlys for the first time. The outbreak might be thereason for the significant decline in live coral cover in 2021. Comprehensive monitoring through regional collaboration is needed.

Predation on a newly-stocked long-spined sea urchin (Diadema antillarum) by the batwing coral crab (Carpilius corallinus) on a coral reef restoration site

This photograph documents a batwing coral crab (Carpilius corallinus) preying on the sea urchin (Diadema antillarum) on a coral reef site enhanced with artificial shelter and staghorn coral. This interaction illustrates an interaction that to be better understood to develop a restoration strategy that harnesses positive ecological processes.

Dispersal of yellowtail kingfish (Seriola lalandi) from a coastal embayment following a recreational fisheries enhancement stocking program: attempts to integrate aquaculture and habitat-based initiatives

Fisheries enhancement initiatives including marine stocking and artificial reef deployments are becoming increasingly common in many parts of the world. Combining the two by releasing hatchery reared fish onto artificial reefs is used in sea-ranching operations but is an approach rarely adopted for recreational fisheries. Yellowtail kingfish (Seriola lalandi) form a valuable recreational fishery in Australia and in 2018 a pilot stocking program was initiated to enhance this fishery. Fish were released onto estuarine artificial reefs in Botany Bay to evaluate if estuarine artificial reefs are suitable release habitat for juvenile yellowtail kingfish and to monitor their dispersal patterns using acoustic telemetry and a tag-recapture program. Both approaches showed similar patterns, indicating juvenile yellowtail kingfish rapidly dispersed from the release location and can travel at least 60 km during their first weeks in the wild. Twenty percent of the acoustically tagged fish entered nearby estuaries to the north and south and tagged fish were also recaptured in these estuaries, indicating that the estuaries provide habitat for juveniles. There was little interaction between stocked fish and two large coastal artificial reefs positioned near Botany Bay. Stocked yellowtail kingfish will likely disperse rapidly from release locations which is consistent with their pelagic life history. While this may present challenges to fisheries managers, increasing release numbers to maintain stocking densities over a broader area may provide a solution. Future releases of fish on coastal natural and artificial reefs are an important next step in refining stocking practices for this species and will help further identify key juvenile habitats.

Morphological and molecular identification of Octopoda (Mollusca: Cephalopoda) paralarvae from the southern Gulf of Mexico

Paralarvae (PL) are crucial to understanding the life cycle and population dynamics of cephalopods. Misidentification of species with similar morphology is a problem that hampers understanding of cephalopod composition and distribution. In this study, we used morphological and molecular approaches to carry out a comprehensive identification of Octopoda PL that inhabit two main areas (Tamaulipas and Yucatán) in the southern Gulf of Mexico (GoM). A total of 189 paralarvae were identified using morphological criteria. Of these, 52 PL were analyzed molecularly by sequencing the mitochondrial cytochrome c oxidase subunit I (COI) gene. We identified four species and five morphotypes. The molecular tools corroborated three of four species, while the molecular sequences of three out of four morphotypes indicated that they belong to three different species. All the genetic sequences had high similarities (99.3%–100%) with previous records. One species and one morphotype could not be sequenced because of unsatisfactory fixation; one morphotype remained as such after the molecular analysis. An identification tree was constructed for the species identified with the molecular approach. The species found off the Yucatán platform were Octopus vulgaris Type I, Octopus americanus, Macrotritopus defilippi, Amphioctopus burryi, A. cf. burryi, Octopus sp., and Callistoctopus furvus. The species identified off the Tamaulipas coast were Octopus insularis and M. defilippi. Paralarvae of O. vulgaris Type I and M. defilippi were the most abundant during 2016–2017. This study provides the first record of Octopoda PL in the southern GoM, including morphological descriptions and molecular sequences of the analyzed taxa.

Revising geographic distributions of eastern Pacific moray eels

Under the influence of climate stressors, species distributions of fishes in the eastern Pacific are shifting, with many species moving poleward. Moray eels (family Muraenidae) are ecologically important predators inhabiting coastal reefs. Due to their cryptic nature and lack of commercial importance, the species distributions of muraenids in the tropical and subtropical eastern Pacific are poorly understood. Here, we document the geographic range size of 33 muraenid species in the eastern Pacific and also report a shift in the established population range of Muraena argus based on recent trapping efforts. We found that 17 species demonstrated shifts in geographic range size, including sampled-range expansions and new occurrences at offshore islands. Eleven species were observed in new biogeographic provinces, primarily in the northward direction to the San Diegan province. Trapping data and local knowledge gathered from fishing cooperatives suggest that M. argus has established populations at least 300 km further north than previously reported. Both the yearly number of reported observations and geographic extent of sampling have increased over time, but the number of recorded extensions has not. These results highlight the importance of compiling data from diverse sources (including museum records, local ecological knowledge, and the non-English scientific literature) as well as the continued value of biodiversity surveys in the eastern Pacific.

Pools of resilience

We describe an extreme habitat for scleractinian corals in intertidal rock pools of southeastern Australia. The pools host a small but hardy subset of coral species despite experiencing conditions beyond those documented for corals anywhere in Australia. Understanding mechanisms behind this may improve insights into climate change adaptation in corals.

First record of synchronous coral spawning in a marginal coral community in Shenzhen, China

Here we present the first documentation of a synchronous coral spawning event in a marginal coral community in Shenzhen. Acropora pruinosa was observed spawning for seven consecutive nights after the full moon, and Platygyra carnosa was observed spawning on the eighth and ninth nights after the full moon.

First report of successful recruitment by conjoined larvae in the brooding scleractinian coral Pocillopora acuta, southern Taiwan

We report the first observation of conjoined larvae (CL) in the scleractinian coral Pocillopora acuta. Colonies at an elevated temperature had a higher ratio of CL (29 °C; 1:200) than colonies at an ambient temperature (26 °C; 1:500). CL demonstrated normal swimming ability and capacity for settlement, metamorphosis, and asexual budding.

Parrotfish target large relocated corals causing restoration bottleneck

Large (30–45 cm in diameter) corals from three species relocated onto a reef in Miami, Florida, USA, experienced significant predation by parrotfish, with several colonies loosing >50% of their live tissue in less than 2 weeks, representing a major source of mortality for restored corals.