Combining population genomics and biophysical modelling to assess connectivity patterns in an Antarctic fish.

Connectivity is a fundamental process of population dynamics in marine ecosystems. In the last decade, with the emergence of new methods, combining different approaches to understand the patterns of connectivity among populations and their regulation has become increasingly feasible. The Western Antarctic Peninsula (WAP) is characterized by complex oceanographic dynamics, where local conditions could act as barriers to population connectivity. Here, the notothenioid fish Harpagifer antarcticus, a demersal species with a complex life cycle (adults with poor swim capabilities and pelagic larvae), was used to assess connectivity along the WAP by combining biophysical modelling and population genomics methods. Both approaches showed congruent patterns. Areas of larvae retention and low potential connectivity, observed in the biophysical model output, coincide with four genetic groups within the WAP: (1) South Shetland Islands, (2) Bransfield Strait, (3) the central and (4) the southern area of WAP (Marguerite Bay). These genetic groups exhibited limited gene flow between them, consistent with local oceanographic conditions, which would represent barriers to larval dispersal. The joint effect of geographic distance and larval dispersal by ocean currents had a greater influence on the observed population structure than each variable evaluated separately. The combined effect of geographic distance and a complex oceanographic dynamic would be generating limited levels of population connectivity in the fish H. antarcticus along the WAP. Based on this, population connectivity estimations and priority areas for conservation were discussed, considering the marine protected area proposed for this threatened region of the Southern Ocean.

Morphology and diet are decoupled in nearshore notothenoids from King George Island, West Antarctica.

Antarctic notothenioid fishes show wide adaptive morphological radiation, linked to habitat preferences and food composition. However, direct comparisons of phenotypic variability and feeding habits are still lacking, particularly in stages inhabiting nearshore areas. To assess these relationships, we collected juveniles and adults of the most common benthic species inhabiting shallow waters off the South Shetland Islands within a similar size range, the plunderfish Harpagifer antarcticus, the black rockcod Notothenia coriiceps, and the marbled rockcod Notothenia rossii. Individual size ranges varied from 44.0 to 98.9 mm standard length (LS) (H. antarcticus), from 95.8 to 109.3 mm LS (N. coriiceps), and from 63.0 to 113.0 mm LS (N. rossii). Notothenioid fish showed different morphospace variability, being larger for H. antarcticus than the other Notothenia species and associated with the position of the posterior end of the operculum, along with the location and relative size of the eye. The evolutionary allometry was low, but the static allometry was much higher, especially for H. antarcticus and N. rossii. The diet was mainly carnivorous, consisting of amphipods and euphausiids. Macroalgae were scarce or totally absent in the gut contents of all species. Only H. antarcticus showed an increase in the prey number and ingested prey volume with fish size. Finally, there was a significant covariation between shape changes and LS in all species (allometric effects), however, not with prey composition, probably due to the small size range or ontogenetic stage and the relative similarity (or lack of contrast) in the benthic environment that they utilized.

Effects of metacercariae of Prosorhynchoides sp. (Trematoda: Bucephalidae) on the swimming ability and blood parameters of the intertidal fish Girella laevifrons (Osteichthyes: Kyphosidae).

Parasites may have various effects on their host's health. It is important to determine the type of the effects but also to decipher the physiological mechanisms underlying a parasitic infection. In this study, swimming ability (by a fixed swim speed test) and haematological analyses (by blood parameters) were compared between juvenile fish Girella laevifrons non-parasitised and parasitised with metacercariae of Prosorhynchoides sp. Fish were infested in the laboratory using natural parasitised mussels. Aerobic swimming time, total erythrocyte and leukocyte counts were compared among four groups of fish: non-parasitised (NP), non-parasitised but manipulated (NPM), parasitised 3 days (PT1), and 10 days (PT2) post-infection. Differentiated haematological components were also compared among NP, PT1 and PT2 fish groups. Parasitised fish (PT1 and PT2) swam between 32% and 55% less time than unparasitised fish. Erythrocyte counts were lower in PT1, indicating anemia, and total leukocyte counts were higher in PT1, showing immune action. Macrophages and basophils were observed only in parasitised fish, independent of the post-infection time. There was a negative correlation between swimming time and leukocyte counts. Increased leukocytes in the blood indicate activation of the innate cellular immune response, which may be metabolically costly for the host. Moreover, the anemia in parasitised fish would reduce the oxygen transport necessary to carry out aerobic exercise, reducing the swimming capacity. In fish several days post-infection (PT2), the erythrocytes count reached normal values, and some kinds of leukocytes decreased in comparison to fish PT1. This suggests that parasitised fish with metacercariae were recovering.

DNA reconciles morphology and colouration in the drunk blenny genus Scartichthys (Teleostei: Blenniidae) and provides insights into their evolutionary history.

The blenniids of the genus Scartichthys are one of the most common fishes of Central and South American Pacific coastal reefs. This being said, Scartichthys spp. remain difficult to identify in the field, and identification is particularly challenging across the c. 6000 km where three of the four currently accepted species are known to occur in sympatry. A reason for this is that the main taxonomic characters from traditional taxonomy are indeed elusive. In addition, at the same time, species can display multiple colour patterns in the field, depending on their ontogenetic stage, habitat association and reproductive behaviour. Overall, molecular characterization is warranted to help address these issues. In this study, the authors have used a novel approach to revise the genus by combining colouration, morphological and molecular data of representative specimens of the four currently valid species and seven described colour patterns. From this, the authors show that only three of the four species should be considered as valid; Scartichthys gigas (Steindachner, 1876), Scartichthys variolatus (Valenciennes, 1836) and Scartichthys viridis (Valenciennes, 1836), whereas Scartichthys crapulatus (Williams, 1990) should be synonymized with S. viridis. In the same way, the analyses in this study show that one of the colour patterns attributed so far only to S. gigas is characteristic of the juvenile stages of S. viridis. The time-calibrated phylogeny of this study shows that this genus is relatively young and that the estimated time of divergence between S. gigas and S. viridis is c. 1.71 Ma. In comparison, the Desventuradas and Juan Fernandez Islands endemic S. variolatus diverged c. 1.95 Ma. The results of this study help to clarify the taxonomy of Scartichthys.

Larval parasitic copepods affect early life history traits of a temperate clingfish.

Larval copepods are frequent parasites that infest fish larvae along the Chilean coast. Because these parasites develop on fish during the early development, when their bodies are fragile and in a recent stage, they can affect the fishes' early life history traits (ELHT). The goal of this study was to determine the effect of parasitic copepods on the ELHT of the larvae of the clingfish Gobiesox marmoratus (Teleostei: Gobiesocidae) using otolith microstructure analysis. Ichthyoplankton samples were collected during austral winter (July and August 2012), in the inner shelf waters off Valparaiso Bay, central Chile. A total of 95 non-parasitized larvae (NPL) and 95 parasitized (PL) with copepods were randomly selected for subsequent analyses. Parasitized larvae of G. marmoratus were larger than NPL. The right otolith tended to be larger than the left otolith in the fish larvae, but with a higher asymmetry in PL. The PL showed larger otoliths-at-size than the NPL, particularly in smaller larvae (< 8 mm of standard length, SL). Nonetheless, parasitized larvae larger than 8 mm SL showed the opposite trend that is smaller-at-size otoliths than NPL. The Gompertz models indicated that the asymptotic length of NPL doubled the length of PL; this suggests that parasitic copepods affect the maximum size attained by the PL. In conclusion, parasitic copepods negatively affect the ELHT of G. marmoratus larvae and the greater asymmetry can be attributed to parasitism.

Environmental determinants in morphospace and diet of the larval blenny Calliclinus geniguttatus from an upwelling ecosystem.

The effects of two contrasting environmental conditions in nearshore waters off central Chile on the diet and morphospace of two cohorts of larval labrisomid blenny Calliclinus geniguttatus were studied using geometric morphometrics and gut content analysis. The two environmental conditions corresponded to (a) a cold period with upwelling-favourable southwesterly winds and a mixed water column of cooler water and (b) a warm period with calm winds and stratified warmer water. During the cold period, fish larvae had a more hydrodynamic head shape, longer jaws and a higher feeding incidence, suggesting a greater food supply due to upwelling events and a possible increase in encounter rates in the turbulent environment. In contrast, the larvae from the warm period had a more robust head shape with smaller jaws and a lower feeding incidence, which was related to higher water temperatures and lower wind intensities. The present study suggests that larvae have a rapid response to environmental changes on a short time scale (i.e., from weeks to months), showing a link between environmental conditions and changes in the phenotypic traits and diet of the larval stages of this cryptobenthic species.

Lunar influences in the diet habits and selectivity of larval clingfish Gobiesox marmoratus.

The influence of the lunar cycle on the feeding habits, feeding success and selectivity was tested in situ on larval stages of the clingfish Gobiesox marmoratus (Gobiesocidae). Gobiesox marmoratus larvae and their prey were collected in the water column during the lunar cycle in austral spring 2015 and 2016, in shallow waters (<30 m depth) of El Quisco, central Chile. Feeding incidence was high (80-100%) throughout the moon cycle. The diet was composed of 32 prey items, being gastropod larvae and invertebrate eggs the most important. Prey composition varied among lunar phases with the lowest prey richness during new moon. During 2016, G. marmoratus larvae ingested the lowest number, but the largest prey during new moon. In spring 2015, there were no significant changes in the abundance of each prey taxon in the water column among moon phases, but in spring 2016 there were significant differences in the abundance of cypris and copepod nauplii, particularly between full and new moon. Feeding selectivity index showed that gastropod larvae were positively selected throughout the lunar cycle during spring 2015. In spring 2016, invertebrate eggs were selectively ingested in full moon and third quarter, but at a new moon G. marmoratus larvae selected gastropod larvae. Mean temperature of the water column and its vertical gradient and nocturnal cloud cover influences the feeding success of larval G. marmoratus. Lunar illumination favoured only an increase of richness of prey items. Therefore, nocturnal cloud cover precludes a greater influence of lunar illumination in the larval trophic ecology of this crypto-benthic fish.

Niche partitioning and morphospace in early stages of two sympatric Diogenichthys species (Myctophidae).

Diet and morphospace of larval stages of two sympatric lanternfish Diogenichthys atlanticus and D. laternatus from the south-east Pacific Ocean were compared and the covariance between both variables was assessed for each species. Diogenichthys atlanticus stomach contents consisted mainly of copepod nauplii and digested remains and this species had a broader niche than D. laternatus, in which stomach contents were highly digested. No dietary overlap was found between both species. The covariance between skull shape and diet for D. atlanticus was given by a wider mouth gape related to the presence of copepod nauplii, whilst for D. laternatus, a shorter snout and posteriorly displaced eye were related to the presence of highly digested stomach contents. Interspecific differences between diets and skull shapes suggest that both species may have undergone morphological or niche divergence to avoid competition, such as feeding at different hours or depth stratification.

Daily growth patterns and age-at-recruitment of the anchoveta Engraulis ringens as indicated by a multi-annual analysis of otolith microstructure across developmental stages.

The anchoveta (Engraulis ringens) plays a key role in the ecology of the Humboldt Current System and is of major economic importance; however, many aspects of its early life history are still poorly understood. In this study, an analysis of daily age and length patterns was carried out using the sagittal otoliths from wild larvae (0-0.2 cm standard length, LS ), pre-recruits (3-6 cm total length, LT ), recruits (7-12 cm LT ) and young adults (12-15 cm LT ). Additionally, variability in growth and age at recruitment (AR ) were evaluated for recruits caught in northern Chile in 1973, 1982, 2009, 2010, 2012, 2013, 2014 and 2015. The age-length relationship showed four allometric patterns that were well described by Laird-Gompertz models. The absolute growth rates at the inflexion point (GAR ) were 0.56, 0.75, 1.22 and 1.16 mm d-1 for larvae, pre-recruits, recruits and young adults, respectively. At the interannual scale, GAR values were always >1 mm d-1 (mean ± S.D. 1.37 ± 0.21 mm d-1 ; range 1.12-1.64 mm d-1 ), irrespective of the season of hatching (i.e. winter v. spring); additionally, in most cases, GAR values were reached before the second month of life (mean ± S.D. 50.47 ± 9.73 days) at c. 4 cm LT (mean ± S.D. 4.22 ± 0.29 cm). Mean AR was < 150 days (112 ± 29 days; range 75-149 days); in contrast, estimates of AR were higher and growth rates were lower in 1973, 1983 and 2000. These results demonstrate very fast growth and early AR of anchoveta in northern Chile, suggesting most fish are removed by the fisheries at very early ages. An evaluation of the implications of these results on stock assessment and management of this species is highly recommended.

Parasites of fish larvae: do they follow metabolic energetic laws?

Eumetazoan parasites in fish larvae normally exhibit large body sizes relative to their hosts. This observation raises a question about the potential effects that parasites might have on small fish. We indirectly evaluated this question using energetic metabolic laws based on body volume and the parasite densities. We compared the biovolume as well as the numeric and volumetric densities of parasites over the host body volume of larval and juvenile-adult fish and the average of these parasitological descriptors for castrator parasites and the parasites found in the fish studied here. We collected 5266 fish larvae using nearshore zooplankton sampling and 1556 juveniles and adult fish from intertidal rocky pools in central Chile. We considered only the parasitized hosts: 482 fish larvae and 629 juvenile-adult fish. We obtained 31 fish species; 14 species were in both plankton and intertidal zones. Fish larvae exhibited a significantly smaller biovolume but larger numeric and volumetric densities of parasites than juvenile-adult fish. Therefore, fish larvae showed a large proportion of parasite biovolume per unit of body host (cm(3)). However, the general scaling of parasitological descriptors and host body volume were similar between larvae and juvenile-adult fish. The ratio between the biovolume of parasites and the host body volume in fish larvae was similar to the proportion observed in castrator parasites. Furthermore, the ratios were different from those of juvenile-adult fish, which suggests that the presence of parasites implies a high energetic cost for fish larvae that would diminish the fitness of these small hosts.

Parasite richness in fish larvae from the nearshore waters of central and northern Chile.

In the present study, we determine the presence of parasites in fish larvae collected from nearshore waters along the northern and central coast of Chile. The parasites were identified to the lowest possible taxonomic level based on morphological and molecular analyses. The fish sample was composed of 5 574 fish larvae. Of these, 3% harboured only larval ectoparasitic copepods whereas no endoparasites were found in the 1 141 fish evaluated for this group of parasites. The parasitic copepods collected were initially classified as 'morphotypes' according to differences in morphological characteristics. They were then analysed using molecular techniques based on the 28S and COI genes. Seven morphotypes of parasitic copepods (mostly at chalimus stages) were recognised: two of the morphotypes belonged to Pennellidae Burmeister, 1835, three to Caligidae Burmeister, 1835 and two were not identified. Only five morphotypes of copepods were analysed using molecular sequences, which confirmed the existence of six species: two pennellids of the genus Trifur Wilson, 1917 and two caligids of the genus Caligus Müller, 1785, plus two additional species that were morphologically different from these taxa. The pennellids were present in several fish species, being generally more prevalent than the caligids, in both the central and northern localities of Chile. Multispecies infections in larval fish were infrequent (< 1%). We conclude that fish larvae were rich in parasites, considering that these hosts exhibited small body sizes and were very young. We suggest that fish larvae could play a role, as intermediate hosts, in the life cycle of the parasitic copepods found.

Environmental DNA reveals temporal variation in mesophotic reefs of the Humboldt upwelling ecosystems of central Chile: Toward a baseline for biodiversity monitoring of unexplored marine habitats.

Temperate mesophotic reef ecosystems (TMREs) are among the least known marine habitats. Information on their diversity and ecology is geographically and temporally scarce, especially in highly productive large upwelling ecosystems. Lack of information remains an obstacle to understanding the importance of TMREs as habitats, biodiversity reservoirs and their connections with better-studied shallow reefs. Here, we use environmental DNA (eDNA) from water samples to characterize the community composition of TMREs on the central Chilean coast, generating the first baseline for monitoring the biodiversity of these habitats. We analyzed samples from two depths (30 and 60 m) over four seasons (spring, summer, autumn, and winter) and at two locations approximately 16 km apart. We used a panel of three metabarcodes, two that target all eukaryotes (18S rRNA and mitochondrial COI) and one specifically targeting fishes (16S rRNA). All panels combined encompassed eDNA assigned to 42 phyla, 90 classes, 237 orders, and 402 families. The highest family richness was found for the phyla Arthropoda, Bacillariophyta, and Chordata. Overall, family richness was similar between depths but decreased during summer, a pattern consistent at both locations. Our results indicate that the structure (composition) of the mesophotic communities varied predominantly with seasons. We analyzed further the better-resolved fish assemblage and compared eDNA with other visual methods at the same locations and depths. We recovered eDNA from 19 genera of fish, six of these have also been observed on towed underwater videos, while 13 were unique to eDNA. We discuss the potential drivers of seasonal differences in community composition and richness. Our results suggest that eDNA can provide valuable insights for monitoring TMRE communities but highlight the necessity of completing reference DNA databases available for this region.

Unraveling the morphological patterns of a subantarctic eelpout: a geometric morphometric approach.

Phenotypic variation in organisms depends on the genotype and the environmental constraints of the habitat that they exploit. Therefore, for marine species inhabiting contrasting aquatic conditions, it is expected to find covariation between the shape and its spatial distribution. We studied the morphology of the head and cephalic sensory canals of the eelpout Austrolycus depressiceps (4.5-22.5 cm TL) across its latitudinal distribution in South Pacific (45°S-55°S). Geometric morphometric analyses show that the shape varied from individuals with larger snout and an extended suborbital canal to individuals with shorter snouts and frontally compressed suborbital canal. There was size variation across the sampled populations, but that size does not have a clear latitudinal gradient. Only 8% of the shape variation relates to this size variation (allometry), represented by a decrease in the relative size of the eye, and a depression of the posterior margin of the head. There were spatial differences in the shape of the head, but these differences were probably caused by allometric effects. Additionally, 2 of the canals of the cephalic lateralis pores and the head shape showed modularity in its development. This study shows that the morphology of marine fish with a shallow distribution varies across distances of hundreds of kilometers (i.e., phenotypic modulation).

Spatio-temporal patterns of the crustacean demersal fishery discard from the south Humboldt Current System, based on scientific observer program (2014-2019).

This study summarises six years of spatio-temporal patterns of the discarded demersal community fauna recorded by onboard scientific observer program for both artisanal and industrial crustacean fisheries between 2014 and 2019, from mesophotic to aphotic depths (96 to 650 m) along the southern Humboldt Current System (28-38°S). In this period, one cold and two warm climatic events were observed during the austral summer 2014, 2015-2016 (ENSO Godzilla), and 2016-2017 (coastal ENSO), respectively. Satellite information showed that Chlorophyll-a concentration varied seasonally and latitudinally, associated with upwelling centres, while equatorial wind stress decreased southward of 36°S. Discards were composed of 108 species, dominated by finfish and molluscs. The Chilean hake Merluccius gayi was dominant and ubiquitous (occurrence, 95% of 9104 hauls), being the most vulnerable species of the bycatch. Three assemblages were identified: assemblage 1 (~200 m deep), dominated by flounders Hippoglossina macrops and lemon crabs Platymera gaudichaudii, assemblage 2 (~260 m deep), dominated by squat lobsters Pleuroncodes monodon and Cervimunida johni and assemblage 3 (~320 m depth), dominated by grenadiers Coelorinchus aconcagua and cardinalfish Epigonus crassicaudus. These assemblages were segregated by depth, and varied by year, and geographic zone. The latter represented changes in the width of the continental shelf, increasing southward of 36°S. Alpha-diversity indexes (richness, Shannon, Simpson, and Pielou) also varied with depth and latitude, with higher diversity in deeper continental waters (>300 m), between 2018-2019. Finally, at a spatial scale of tens of kilometres, and a monthly basis, interannual variations of biodiversity occurred in the demersal community. Surface sea temperature, chlorophyll-a, or wind stress did not correlate with discarded demersal fauna diversity of the crustacean fishery operating along central Chile.

The effects of a parasitic copepod on the recent larval growth of a fish inhabiting rocky coasts.

Parasites can infect larval, juvenile or adult marine fishes; however, the effects of parasites on the growth and condition of fish larvae have seldom been investigated. This study analysed the effects of a parasitic copepod on the larval growth of the Chilean triplefin Helcogrammoides chilensis (Tripterygiidae) based on the microstructure of the sagittal otoliths. Fish larvae were collected during the austral spring of 2010 off central Chile. Their body length ranged from 5.1 to 16.6 mm (2 to 57 days old). They were parasitised by a penellid larval copepod that was always externally attached to the ventral side of the fish's gut. The prevalence of the copepod ranged from 2.7% to 20.8%, with one to four parasites per fish larva. Relationships between otolith size (radius, perimeter) and larval size were equal for parasitised and unparasitised fish larvae (P > 0.05). Larval growth was also similar for unparasitised (0.21 mm/day) and parasitised fish larvae (0.19 mm/day) (P > 0.05). However, a comparison of same-aged larvae showed that the larvae with copepods were smaller in both length and estimated body volume than the larvae without copepods. The Recent Otolith Growth Index, indicated that larval H. chilensis with copepods showed a reduction in recent growth and condition compared with those without evidence of copepods (P < 0.05). Nevertheless, a higher parasite load (two vs. one pennellids) did not decrease the condition of the larval fish. The infestation of pennellids on coastal fish larvae may therefore induce an increase in the pelagic larval duration and potentially affect the settlement rates of this intertidal fish.

Modelling seasonal patterns of larval fish parasitism in two northern nearshore areas in the Humboldt Current System.

Macro- and micro-environmental factors modulate parasite loads in fish, determining parasitic abundances, diversity, and interaction dynamics. In this study, seasonal variations in larval ectoparasites on fish larvae in the northern Humboldt Current System (HCS) were evaluated using a delta-gamma generalized linear model to predict their occurrence frequencies. Fish larvae were collected from two nearshore areas during austral spring-summer and autumn-winter. Only five (of 38) larval fish species were parasitized by copepods: Gobiesox marmoratus, Ophiogobius jenynsi, Helcogrammoides cunninghami, Myxodes sp., and Auchenionchus crinitus. A binomial model showed that the presence/absence of parasitized fish larvae varied among the fish species and their larval abundances, while a positive delta-gamma model showed that ectoparasite frequency varied among the seasons and fish species. Seasonal variations in parasitized fish larvae frequency could be associated with host and parasite reproductive processes, which are related to oceanographic features responsible for larval retention and subsequent higher infestation probabilities. Host length was positively correlated with ectoparasite length, suggesting early infection and combined growth until the detachment of the ectoparasite. Our results suggest that infestation patterns in larval fish species can be identified using delta-gamma models and that they respond to local (retention) and high-scale (HCS) processes.

Year-round high abundances of the world's smallest marine vertebrate (Schindleria) in the Red Sea and worldwide associations with lunar phases.

Very little is known about the ecology and biology of the smallest marine vertebrates, fishes in the genus Schindleria. Even though over half of named Schindleria species have been identified in the Red Sea, the collection of only very few specimens has been documented. Here, we assessed abundance patterns of nearly two thousand Red Sea long dorsal fin (LDF) adults and found evidence for putative seasonal and spatial differences, likely related to differing habitat and environmental conditions. The highest abundances were outside local seasonal temperature extremes and decoupled from peaks of coral reef fish recruitment. We also found evidence for global trends in abundances related to lunar cycles using our Red Sea data and that from a recently published large collection of specimens from the DANA Expedition (1928-1930). The abundance of adult LDF Schindleria in relation to lunar phases differed significantly, with most Schindleria caught outside the full moon, and mostly during the new moon in the Red Sea and the 3rd quarter moon in the DANA collection. We further suggest that the abundances of Schindleria at coral reefs may be related to reproductive cycles and that these cycles may be timed with the moon as back-calculations of hatch dates from otoliths from the Red Sea significantly resulted after the new moon, making Schindleria the fastest-lived coral reef fish with the shortest generation times. Schindleria could be the most numerous coral reef fish in the world, for which we encourage increased research.

Larval development and osteology of Callanthias platei (Teleostei: Callanthiidae) from Desventuradas Islands, South Pacific.

Larvae of the Juan Fernández Splendid Perch, Callanthias platei Steindachner, 1898 (Teleostei: Callanthiidae), are described for the first time. The five available specimens, ranging from 3 mm notochord length (NL) to 6.1 mm standard length (SL), were collected with plankton nets near Desventuradas Islands, Southeast Pacific, during the austral spring of 2015 and 2016. The larvae are deep bodied with a narrow caudal peduncle, a large head and a triangular, coiled gut. The pigmentation is scarce in preflexion larvae but increases after flexion. All individuals have several groups of head spines: anterior and posterior preopercular, interopercular, subopercular, opercular and supracleithral. The formation of all fins occurs early in development, with the pectoral fins appearing first and the pelvic fins last. The osteological development of the skull, vertebral column, fins, and scales are described.

Global phylogeography suggests extensive eucosmopolitanism in Mesopelagic Fishes (Maurolicus: Sternoptychidae).

Fishes in the mesopelagic zone (200-1000 m) have recently been highlighted for potential exploitation. Here we assess global phylogeography in Maurolicus, the Pearlsides, an ecologically important group. We obtained new sequences from mitochondrial COI and nuclear ITS-2 from multiple locations worldwide, representing 10 described species plus an unknown central South Pacific taxon. Phylogenetic analyses identified five geographically distinct groupings, three of which comprise multiple described species. Species delimitation analyses suggest these may represent four species. Maurolicus muelleri and M. australis are potentially a single species, although as no shared haplotypes are found between the two disjunct groups, we suggest maintenance of these as two species. Maurolicus australis is a predominantly southern hemisphere species found in the Pacific, Indian and southern South Atlantic Oceans, comprising five previously allopatric species. M. muelleri (previously two species) is distributed in the North Atlantic and Mediterranean Sea. Maurolicus weitzmani (previously two species) inhabits the eastern equatorial Atlantic, Gulf of Mexico and western North and South Atlantic. Maurolicus mucronatus is restricted to the Red Sea. No Maurolicus have previously been reported in the central South Pacific but we have identified a distinct lineage from this region, which forms a sister group to Maurolicus from the Red Sea.

Spatial patterns of continental shelf faunal community structure along the Western Antarctic Peninsula.

Knowledge of continental shelf faunal biodiversity of Antarctica is patchy and as such, the ecology of this unique ecosystem is not fully understood. To this end, we deployed baited cameras at 20 locations along ~ 500 km of the Western Antarctic Peninsula (WAP) at depths from 90 to 797 m. We identified 111 unique taxa, with mud bottom accounting for 90% of the dominant (≥ 50% cover) habitat sampled. Amphipoda comprised 41% of the total maximum number of individuals per camera deployment (MaxN) and occurred on 75% of deployments. Excluding this taxon, the highest MaxN occurred around King George/25 de Mayo Island and was driven primarily by the abundance of krill (Euphausiidae), which accounted for 36% of total average MaxN among deployments around this island. In comparison, krill comprised 22% of total average MaxN at Deception Island and only 10% along the peninsula. Taxa richness, diversity, and evenness all increased with depth and depth explained 18.2% of the variation in community structure among locations, which may be explained by decreasing ice scour with depth. We identified a number of Vulnerable Marine Ecosystem taxa, including habitat-forming species of cold-water corals and sponge fields. Channichthyidae was the most common fish family, occurring on 80% of all deployments. The Antarctic jonasfish (Notolepis coatsorum) was the most frequently encountered fish taxa, occurring on 70% of all deployments and comprising 25% of total MaxN among all deployments. Nototheniidae was the most numerically abundant fish family, accounting for 36% of total MaxN and was present on 70% of the deployments. The WAP is among the fastest warming regions on Earth and mitigating the impacts of warming, along with more direct impacts such as those from fishing, is critical in providing opportunities for species to adapt to environmental change and to preserve this unique ecosystem.