Deep-water Fish Research Articles

Prey diversity in the deep ocean: metabarcoding feeding ecology of the commercially important queen snapper in the US Caribbean

The queen snapper, Etelis oculatus, is experiencing a growing fishery presence across the wider Caribbean, yet our understanding of its distribution, biology, and ecology remains limited. To address this gap, we investigated the feeding ecology of this demersal deep-water snapper using two molecular approaches: single-species barcoding and multispecies metabarcoding. Between November 2019 and July 2020, we collected 157 queen snapper from seven locations along the west coast of Puerto Rico. Our analysis identified a diverse array of prey items in the stomachs, comprising 61 species from 31 families, 18 orders, and 38 genera. Our findings suggest that E. oculatus is a large carnivore, primarily preying on squids, shrimps, and deep-water fishes. Notably, common fish prey included Diaphus brachycephalus, D. dumerilii, Dasyscopelus selenops, Coccorella atlantica, Sigmops elongatus, and Zaphotias pedaliotus. In contrast, prevalent invertebrate prey consisted of Abralia veranyi, Doryteuthis pealeii, Abralia redfieldi, Oplophorus gracilirostris, and Systellaspis debilis. Although our data suggest potential variation in diet composition across locations, definitive conclusions remain elusive. However, we observed heightened prey richness at seamount Pichincho, possibly attributable to the high structural complexity of the karst terrain on the seafloor. Additionally, we noted variation in prey species composition across size classes, with certain species more prevalent in larger or smaller queen snapper. Given the challenge of examining the prey of deep-water fish species, our study showcases the utility of both single-species barcoding and multispecies metabarcoding methodologies in characterizing the dietary range of queen snapper and similar demersal deep-water carnivorous fishes. The multispecies metabarcoding approach, in particular, offers a rapid, comprehensive, and effective means of identifying prey species. As the commercial value of the queen snapper continues to rise, our investigation into its feeding behavior provides critical baseline information for future species management efforts. By enhancing our understanding of its ecological dynamics, we aim to contribute to informed conservation and sustainable fisheries practices in the region.

Variation in Isotopic Trophic Niche of Sablefish (Anoplopoma fimbria) and Shortraker Rockfish (Sebastes borealis) in the Northeast Pacific

Sablefish (Anoplopoma fimbria, Anoplopomatidae) and shortraker rockfish (Sebastes borealis, Sebastidae), co-occur in deepwater marine habitats in the northeast Pacific. Both species are economically valuable, but their ecologies are not well known. We used stable isotope analysis of carbon and nitrogen to explore isotopic niches of A. fimbria and S. borealis in two distinct locations—a deep strait in the inside passage area and an open coastal area of the continental shelf, both in southeast Alaska, USA. Anoplopoma fimbria and S. borealis exhibited similar positions of isotopic niches based on nitrogen and carbon isotopic ratios, suggesting potential interspecific competition, especially in the inside location. In addition, S. borealis had a smaller niche breadth compared to A. fimbria in the coastal location. Both species had enriched nitrogen and carbon isotopic ratios in the inside location compared to the coastal location. Differences in isotopic niches between these two locations suggest the possibility of location-specific variation in isotopic niches of these two species of widespread, abundant deepwater fishes.

Differences in Waterbird Communities between Years Indicate the Positive Effects of Pen Culture Removal in Caizi Lake, a Typical Yangtze-Connected Lake

Considering the negative effects of wetland degradation, various measures have been implemented to restore wetland habitats for aquatic organisms, and their effectiveness levels must be assessed. To reduce the effects of aquaculture on aquatic communities, pen culture facilities, which are widely distributed in Yangtze-connected lakes, were removed in 2018. We surveyed and compared waterbird communities in Caizi Lake during the four months before (2017–2018) and after net pen removal (2021–2022) to evaluate their effect on the diversity and species composition of wintering waterbirds. After net pen removal, the richness and number of individual waterbird species increased, whereas the Shannon–Wiener diversity index did not change because the increase in the bird number throughout the year was mostly associated with a few species. The response of individual numbers of different guilds to the removal of net pens differed. The number of deep-water fish eaters, seed eaters, and tuber feeders increased, whereas that of invertebrate eaters decreased. The species composition also changed, particularly in the northeastern and southwestern parts of the lake. Differences in waterbird communities between the winters of 2017–2018 and 2021–2022 indicated that net pen removal had a positive impact on waterbird communities.

Adaptive Evolution of Nearctic Deepwater Fish Vision: Implications for Assessing Functional Variation for Conservation.

Intraspecific functional variation is critical for adaptation to rapidly changing environments. For visual opsins, functional variation can be characterized in vitro and often reflects a species' ecological niche but is rarely considered in the context of intraspecific variation or the impact of recent environmental changes on species of cultural or commercial significance. Investigation of adaptation in postglacial lakes can provide key insight into how rapid environmental changes impact functional evolution. Here, we report evidence for molecular adaptation in vision in 2 lineages of Nearctic fishes that are deep lake specialists: ciscoes and deepwater sculpin. We found depth-related variation in the dim-light visual pigment rhodopsin that evolved convergently in these 2 lineages. In vitro characterization of spectral sensitivity of the convergent deepwater rhodopsin alleles revealed blue-shifts compared with other more widely distributed alleles. These blue-shifted rhodopsin alleles were only observed in deep clear postglacial lakes with underwater visual environments enriched in blue light. This provides evidence of remarkably rapid and convergent visual adaptation and intraspecific functional variation in rhodopsin. Intraspecific functional variation has important implications for conservation, and these fishes are of conservation concern and great cultural, commercial, and nutritional importance to Indigenous communities. We collaborated with the Saugeen Ojibway Nation to develop and test a metabarcoding approach that we show is efficient and accurate in recovering the ecological distribution of functionally relevant variation in rhodopsin. Our approach bridges experimental analyses of protein function and genetics-based tools used in large-scale surveys to better understand the ecological extent of adaptive functional variation.

Spatiotemporal variability in diet composition of Greenland halibut (Reinhardtius hippoglossoides) from the eastern Canadian Arctic.

Greenland halibut (Reinhardtius hippoglossoides) sustain one of the most lucrative fisheries in the eastern Canadian Arctic and Labrador Sea. This species also plays an important role in food web connectivity and benthic-pelagic coupling. Despite the relatively rich knowledge of this species, R. hippoglossoides ecology in these specific areas remains poorly understood. The main aim of this study was to characterize the diet of this deepwater fish in the Labrador Sea and Davis and Hudson Straits and characterize the predator-prey relationship with northern shrimp (Pandalus borealis), another commercially important species in the region. Stomach contents analyses were conducted on 1199 fish captured from 2018 to 2020. Small specimens (<20 cm) fed on invertebrates, whereas larger individuals (>60 cm) fed primarily on fish, indicative of size-related changes in diet composition. The relative abundance of Pandalus shrimp species in the environment was reflected in the diet. Location appeared to be the most influential variable on feeding patterns. Distinct oceanographic conditions among areas, resulting in differences in prey availability, could explain these results. Arctic cod (Boreogadus saida) and redfish (Sebastes sp.) were selected in locations where fish prey were the most abundant. These results shed light on the opportunistic nature of R. hippoglossoides and its preference for fish at large size. With the rapidly changing oceanographic conditions of Arctic waters, a distributional change in the biomass of shrimp is expected. Results suggest that an increase in abundance of predatory groundfish species in the system (e.g., Sebastes sp.) could lead to acute predation on shrimp and competition with R. hippoglossoides. By revealing key trophic links within the demersal ecosystem, this work provides valuable information on the development of ecosystem approaches to fisheries management for the region.

Matching an Old Marine Paradigm: Limitless Connectivity in a Deep-Water Fish over a Large Distance.

Investigations of population structuring in wild species are fundamental to complete the bigger picture defining their ecological and biological roles in the marine realm, to estimate their recovery capacity triggered by human disturbance and implement more efficient management strategies for fishery resources. The Blackspot Seabream (Pagellus bogaraveo, Brünnich 1768) is a commercially valuable deep-water fish highly exploited over past decades. Considering its exploitation status, deepening the knowledge of intraspecific variability, genetic diversity, and differentiation using high-performing molecular markers is considered an important step for a more effective stock assessment and fishery management. With one of the largest efforts conceived of and completed by countries overlooking the Atlantic and Mediterranean coasts in recent years, a total of 320 individuals were collected from different fishing grounds in the Mediterranean Sea and Atlantic Ocean and analysed using 29 microsatellite loci. We applied multiple statistical approaches to investigate the species' connectivity and population structure across most of its described distribution area. Considering the incomplete knowledge regarding the migratory behaviour of adults, here we suggest the importance of egg and larval dispersal in sustaining the observed genetic connectivity on such a large geographical scale.

Small-scale fishing has affected abundance and size distributions of deepwater snappers and groupers in the MesoAmerican region

Deepwater fisheries in the Caribbean Sea are poorly studied and mostly unmanaged, despite their importance to local economies and food security. In the MesoAmerican region, deepwater fisheries are nearshore and easily accessible in many locations by small vessels, but historical and contemporary fishing effort varies by country. We used standardized fishery-independent methods, including vertical longlines and baited remote underwater video (BRUV) to assess the relative abundance and distribution of deepwater (100–550 m) snappers and groupers in Belize and Honduras. Fishery-dependent samples were used to supplement spatial distribution and body length data. Gathered data revealed that Belize, with a smaller fishing population and shorter history of deepwater fishing, had overall higher abundance of groupers and snappers and that fish were significantly larger than those in Honduras, which has a well-established and larger deepwater fishery. Water temperature was found to influence the abundance and occurrence of deepwater snappers more than depth. Deepwater snappers were widely-distributed throughout available habitat in both countries, but groupers were more patchy, and rarely encountered in the more heavily fished areas off Honduras. Our results suggest that a precautionary approach to fisheries management and targeted biological research of these stocks is required, which is particularly relevant for Belize, where climate change and overfishing mitigation measures are focused on an expansion of the deepwater fishery.

Length–weight relations of 39 continental-shelf and deep-water fishes (Actinopterygii) from northwestern Gulf of México

Fishes from the northwestern Gulf of Mexico were surveyed during four oceanographic campaigns (February and October 2016, June and September 2017) using a shrimp trawl net and benthic sled net in 20 locations at depths that ranged from 43 to 3608 m. Length–weight relations (LWR) were estimated for 39 fish species (in alphabetical order): Bembrops gobioides (Goode, 1880); Centropristis philadelphica (Linnaeus, 1758); Chauliodus sloani Bloch et Schneider, 1801; Chlorophthalmus agassizi Bonaparte, 1840; Chloroscombrus chrysurus (Linnaeus, 1766); Citharichthys spilopterus Günther, 1862; Coelorinchus caelorhincus (Risso, 1810); Cyclopsetta chittendeni Bean, 1895; Cyclothone alba Brauer, 1906; Cyclothone braueri Jespersen et Tåning, 1926; Cyclothone pseudopallida Mukhacheva, 1964; Dibranchus atlanticus Peters, 1876; Epigonus pandionis (Goode et Bean, 1881); Fowlerichthys radiosus (Garman, 1896); Laemonema goodebeanorum Meléndez et Markle, 1997; Lagocephalus laevigatus (Linnaeus, 1766); Lepophidium brevibarbe (Cuvier, 1829); Lutjanus campechanus (Poey, 1860); Malacocephalus occidentalis Goode et Bean, 1885; Merluccius albidus (Mitchill, 1818); Micropogonias furnieri (Desmarest, 1823); Monolene sessilicauda Goode, 1880; Ogcocephalus declivirostris Bradbury, 1980; Peristedion greyae Miller, 1967; Porichthys plectrodon Jordan et Gilbert, 1882; Prionotus longispinosus Teague, 1951; Prionotus paralatus Ginsburg, 1950; Pristipomoides aquilonaris (Goode et Bean, 1896); Rhynchoconger flavus (Goode et Bean, 1896); Sardinella aurita Valenciennes, 1847; Saurida brasiliensis Norman, 1935; Sternoptyx diaphana Hermann, 1781; Symphurus diomedeanus (Goode et Bean, 1885); Synagrops bellus (Goode et Bean, 1896); Trachurus lathami Nichols, 1920; Trichiurus lepturus Linnaeus, 1758; Trichopsetta ventralis (Goode et Bean, 1885); Urophycis cirrata (Goode et Bean, 1896); Zalieutes mcgintyi (Fowler, 1952). The fish species studied represented 28 families (in alphabetical order): Antennariidae, Batrachoididae, Bembropidae, Bothidae, Carangidae, Chlorophthalmidae, Congridae, Cyclopsettidae, Cynoglossidae, Dorosomatidae, Epigonidae, Gonostomatidae, Lutjanidae, Macrouridae, Merlucciidae, Moridae, Ogcocephalidae, Ophidiidae, Phycidae, Sciaenidae, Serranidae, Sternoptychidae, Stomiidae, Synagropidae, Synodontidae, TetraodontidaeTrichiuridae, Triglidae. A new maximum standard length (SL) was recorded for Cyclothone alba, C. braueri, C. pseudopallida, and Lepophidium brevibarbe. A positive allometric growth was reported in nine species, negative allometric growth in 16 species, and isometric growth in 14 species.

Application of the bomb radiocarbon chronometer with eye lens core Δ14C for age validation in deepwater reef fishes

Eye lens core Δ14C of Gulf of Mexico outer shelf and upper slope reef fishes matched a regional Δ14C reference time series, but otolith cores were depleted in 14C relative to the reference series. This is due to C in eye lens protein being derived from metabolic sources, with the ultimate source being epipelagic phytoplankton. In contrast, otolith C is derived mainly (70%–80%) from dissolved inorganic C, which is depleted in 14C beyond the epipelagic. Analyzing Δ14C in eye lens cores provides a novel approach for validating age estimates of deepwater (&gt;200 m) fishes, which were unresolved in earlier applications of the bomb 14C chronometer.

Biological features of nine deep-water fishes from the midslope of the Northwest African coast

The size distribution, sex ratio, spawning activity, and maturity of Alepocephalus bairdii, Alepocephalus productus, Alepocephalus rostratus, Bathygadus favosus, Bathygadus melanobranchus, Nezumia aequalis, Mora moro, Trachyscorpia echinata and Hoplostethus mediterraneus inhabiting the middle slope off Northwest Africa were analysed. Maturation takes place during the winter months, when a high proportion (>62%) of large individuals were observed in the mature, spawning or postspawning stage, with the exception of H. mediterraneus (57.3%). Negative allometric growth was recorded as a general pattern in both sexes, but isometric growth was recorded in females of A. productus, A. rostratus, and B. melanobranchus. Positive allometric growth was only observed in females of T. echinata. The length frequency distribution showed significant differences between sexes, except in A. productus and A. bairdii. Females of Macrouridae species were found to be larger and heavier than males. Sex ratios were generally unbalanced, but no bias was observed in N. aequalis, T. echinata, and H. mediterraneus. Relative size at sexual maturity ranged mainly between 0.66 and 0.72, but B. favosus, H. mediterraneus, and N. aequalis showed lower values (0.54–0.61). Sexual maturity is reached mainly at a size between 1 and 5 cm smaller in males than in females, except in A. bairdii and T. echinata.

THE ENDEMIC MARINE FISH FAUNA FROM THE EASTERN PARATETHYS RECONSTRUCTED FROM OTOLITHS FROM THE MIOCENE (MIDDLE SARMATIAN S.L.; BESSARABIAN) OF JURKINE (KERCH PENINSULA, CRIMEA)

Reconstructing fossil bony fish faunas using otoliths is a well-established method that allows a diverse and dense record in time and space to be assembled. Here we report about a rich otolith-based fish fauna from the middle Sarmatian s.l. (middle Bessarabian) from Jurkine, Kerch Peninsula, Crimea. The study is based on more than 5,000 specimens constituting 36 different species, 24 of which are new and 2 remain in open nomenclature. This assemblage represents the first major otolith association described from the Bessarabian. It also represents a fish fauna from the last continuous restricted marine environment that evolved in the Eastern Paratethys, was recruited from the Badenian/Tarkhanian fauna, and was not affected by the subsequent Khersonian crisis. The association of otoliths is characterized by a high content of endemic fishes that derived from the relatively well-known early Sarmatian s.l. (Volhynian) fish fauna, and it contains certain faunal elements that were trapped in the then-secluded Eastern Paratethys and did not range into younger strata. This forced endemic evolution explains the unusually high percentage of new taxa.&#x0D; The fish fauna is dominated by stenohaline marine shelf fishes apparently recruited from the Konkian and earlier Sarmatian s.l. (Volhynian) fauna after the Karaganian crisis. The families Gobiidae and Gadidae benefited most in this restricted marine environment, while deep-water fishes disappeared with the Karaganian crisis. In this study, we discuss the further evolution of Eastern Paratethyan fishes as far as can be reconstructed from the relatively limited data from post-Bessarabian strata, and we also outline targets for future research in the field.&#x0D; The stratigraphic sequence of the Jurkine section is being revised based on a detailed suite of benthic foraminifera. Implications for the stratigraphy of the middle and upper Sarmatian s.l., their boundary, and the paleoenvironments of this part of the Kerch Peninsula are discussed.

Natural mortality estimations for beaked redfish (Sebastes mentella) – A long-lived ovoviviparous species of the Northeast Arctic

Beaked redfish (Sebastes mentella) is one of the few commercially important fish species producing living offspring. Like many other deep-water fishes, it is slow growing, late maturing and long-lived, getting as old as 65 years or even 75 years in some populations. The stock in the Norwegian and Barents Seas is analytically assessed since 2012, assuming a natural mortality (M) of 0.05 yr−1 across all ages, based on Hoenig’s longevity related estimator. Since then, several reviews and new studies have been published, affording a re-evaluation of the natural mortality in the assessment model. We estimated natural mortality of beaked redfish using 48 different estimators in two categories, either estimating M across the population or dependent on age, length or weight. The obtained estimates were highly variable, ranging from 0.01 to 0.32 yr−1 for estimates across the population, and 0.05–0.62 yr−1 for age or size dependent median-M. These wide ranges demonstrate the sensitivity of SSB to the input parameters as well as the pitfalls of using estimators developed for distant taxa. Of the 48 estimates, 20 were considered as potential candidates for updating the stock assessment model, yet not all of these were realistic. The frequency distribution of the estimators showed a peak around a value of 0.07 yr−1, lowering the estimated spawning stock biomass in the last year by about 300 kt but keeping it above the precautionary reference point for the stock. Estimators across the life-history of beaked redfish indicate a potential underestimation of natural mortality for early and overestimation for late age classes. Age and size related estimators are promising for the older ages but tend to extreme estimates for the early ages, which deserves further investigation.

Seamount seascape composition and configuration shape Southwest Indian Ridge fish assemblages

Seamounts are commercially important fishing grounds. Yet, little is known about their physical characteristics as fish habitat, important for informing conservation and ecosystem-based management.This study examines how multiscale seabed spatial heterogeneity influences commercially important fish families at three Southwest Indian Ridge seamounts (Coral Seamount, Melville Bank and Atlantis Bank). We quantified seascape heterogeneity from bathymetry and geomorphological habitat maps and identified 15 focal fish families from video data. Fish-habitat associations were examined using spatial pattern metrics that measured terrain morphology, seascape composition (variety and relative abundance of patch types) and seascape configuration (spatial arrangement of patches). Broader seascape context was characterised by geographic location and water depth. Multivariate regression trees and random forests modelled fish-habitat associations and identified the most influential explanatory variables.Assemblage characteristics and individual families were strongly influenced by geographic location and depth, and at finer scales (500 m buffers) seascape composition and configuration helped explain fish-habitat associations. Spatially continuous summit habitat and complex shaped ridge features supported high abundance and diversity of commercial fish families. Metrics of seascape composition and configuration (i.e., habitat size, shape and structural connectivity) had higher predictive power than the terrain metrics commonly used in developing proxies for deep-water fish species and biodiversity.These outcomes indicate that seascape metrics, commonly applied on land and in shallow marine environments, are also relevant environmental predictors of fish distributions in deep-sea environments. We highlight strong context dependency and depth-specific associations that hinder attempts to draw wider generalisations on fish-seascape linkages for seamounts.

Effects of capture on acute and long-term reflex impairment, survival, and health of a deepwater fish: Shortspine thornyhead (Sebastolobus alaskanus).

Shortspine thornyhead (Sebastolobus alaskanus) are a benthic, deepwater species in the family Scorpaenidae. They have been tagged annually in Alaska since 1992, but have a low tag return rate of 1.6%. This may be at least partially attributed to post-release mortality related to capture. In this study, 21 shortspine thornyhead were caught on bottom hook-and-line longline gear and immediately given reflex tests. Eighteen were transported to the laboratory and held for 10–42 days, given reflex tests again, and then given postmortem examinations, including histopathology of tissues; three were given postmortem examinations after reflex tests on the vessel. There were no histological findings that could be directly linked to capture and holding; however, there were occurrences of myxozoan (protozoa) and metazoan (nematode) parasites, sometimes associated with minor inflammation. The vibration response reflex was found in only 24% of fish on deck and in 56% of fish after holding in the laboratory. The vestibular-ocular response was present in 47% of fish on deck and 89% of fish in the laboratory. A fish’s ability to right itself was successful on deck in 43% of fish (an additional 19% responded slowly) and 100% in the laboratory. Some reflex impairments may be permanent or may take more than days or weeks to improve. Reflex responses to other tests, the tail grab, gag, and operculum flare, were 95–100% successful on deck and later in the laboratory. A lack of reflexes may increase the risk of predation after release and may affect other behaviors related to survival and productivity.

How do El Niño Southern Oscillation (ENSO) Events Impact Fish Catch in Sarawak Water?

The response of chlorophyll to climate variability plays an important role in regulating the regional marine ecological environment and carbon cycle. This study focuses on the impact of changes in chlorophyll on the catches of deep-water fish and offshore fish. The chlorophyll factors from satellite image MODIS were analysed during La Niña in 2008/2011 and El Niño in 2015/2016. Remote sensing reflectance’s 443 nanometres and 555 nanometres were utilized to examine the bias of the chlorophyll concentration, Thus the higher phytoplankton absorption coefficient at 443, and backscattering coefficient for dissolved and detrital material stated the more phytoplankton biomass and higher suspended sediment concentration. The results found that the fish catch during El Niño is higher at 295572 metric tons compared to during La Niña which is 255783 metric tons. The El Niño event was found to have experienced an increase in catch of 29789 metric tons. This is due to the influence of the change in the mean value of the concentration in the study area of 0.31 mg-3 during La Niña compared to during El Niño 0.4 m mg-3. A decrease in the average value concentration of -0.09 mg-3 resulted in a decrease in the number of catches. In addition, the maximum value of chlorophyll concentration was also found to be high during El Niño which is 22 m mg-3 compared to during La Niña which is 18 m mg-3. The high distribution of chlorophyll-a is in the coastal areas of Sarawak, which explains why the coastal fish catches are higher than in the deep sea. It is concluded that the distribution of chlorophyll concentration is different during the occurrence of ENSO. This may result in different fishing rates in the study area. Remote sensing technology successfully explains why fish catches during El Niño are higher than during La Niña based on different chlorophyll dispersions. The provision of information in this space is very important to fishermen to reduce operating costs.

An investigation of bubble resonance and its implications for sound production by deep-water fishes.

Although the continental slope and abyss comprise the largest habitat on earth, the absence of documented fish sounds from deep waters is striking. Fishes with sexually dimorphic muscles attached to their swim bladders suggests that sounds are likely used in male courtship on the upper, mid and lower continental slope. To investigate the effects of environmental extremes on fish sound production, the acoustic behavior of a driven bubble is examined. This study is also relevant to target strength of sonar returns from fish and hearing in auditory specialist fishes. A bubble is a classic, if imperfect, model for swim bladder behavior since the swim-bladder wall is an anisotropic viscoelastic structure responsible for rapid damping. Acoustic properties of bubbles-including far-field resonant frequency, damping factor, and quality factor-are calculated in warm and cold surface conditions and in cold deep-water (depths 1000 m, 2000 m, and 3500 m) conditions using parameters for oxygen and nitrogen, the dominant gases in swim bladders. The far-field resonant frequency and damping factor of a bubble increase with depth, and the scattering cross-section and quality factor decrease with depth. These acoustic properties scale with undamped oscillation frequency of the bubble and do not vary significantly due to gas type or temperature. Bubbles in the deep-water environments are much less efficient radiators of sound than bubbles near the surface because the far-field radiated power for the same excitation decreases with depth. A bubble at depth 3500 m has a 25 dB loss in radiated sound power compared to the same-radius bubble at the surface. This reduction of radiation efficiency in deep water likely contributes to the absence of fish sound recordings in those environments.

A structured deepwater fish community in an isolated benthic feature off Southern California

Between September and November in 1995 and 1998–2011, we conducted surveys of demersal fishes and their associated benthic habitats using direct observations from human-occupied vehicles over the Footprint, an isolated submerged ridge located seawards of the Santa Cruz Island- Anacapa Island Passage, Southern California, extending over bottom depths of about 94–500 m. The observed fish fauna, consisting of 127,351 individuals of at least 79 species, was dominated by rockfishes (genus Sebastes; 94.5% of individuals, 47% of species). The Footprint is home to a complex of benthic habitats that are occupied by a number of fish assemblages. These were defined by bottom depth, habitat type, and the environmental tolerances and preferences of each species. While the habitat-limited benthic species that occupy the shallower parts of the Footprint are isolated from the Santa Cruz Island and Anacapa Island shelves, the fishes living on the Footprint are not reproductively isolated. Rather, through a web of connections, the fishes of the Footprint are likely well integrated into the Southern California Bight. This connectivity, flowing towards and away from the Footprint, means that events hundreds or thousands of kilometers away may have profound effects on the fish assemblages of this feature. For example, economically important species were relatively uncommon, possibly the result of past overfishing locally and a lack of immigration from other regions.

Fishing opportunities for the deepwater cardinalfish ( Epigonus crassicaudus ) in the continental shelf break along central Chile

Spatial patterns in fish distribution determine most fishing opportunities and tactics learned by fishers. To determine fishing opportunities and recurrent fishing grounds of deepwater fish such as the cardinalfish (Epigonus crassicaudus) in the south-central zone of Chile, we analyzed records of fishing logs covering the period 1999–2007. Fishing trawls covered from Topocalma (34º06'S) to northwest Corral (39º52'S), and we compared the position of individual fishing hauls (Euclidean distance) applying a hierarchical agglomerative clustering technique. The clusters obtained represented spatially distributed fishing opportunities (n = 28), which were visited occasionally (<10 fishing hauls) or regularly (>50 fishing hauls) to fishing for cardinalfish. The recurrent fishing opportunities (n = 7) were distributed discretely, from Constitución (35°19'S) to northwest Mocha Island (38°23'S) along the continental shelf slope and between 313 and 333 m depth. The species composition in the bycatch and the catch per unit effort trends allow us to identify secondary species and locally depleted fishing opportunities, the last occurring close to main fishing ports.

A Dendrophyllia ramea Population in the Ionian Sea (Central Mediterranean Sea) Threatened by Anthropogenic Impacts

This study reports the first attempt to quantitatively describe a Dendrophyllia ramea population on the Apollo bank (Ionian Sea), revealed in summer 2021 through a remotely operated vehicle (ROV) survey. The habitat description, bathymetric distribution, population density, and structure of the species were assessed by image analysis. A well-developed population of D. ramea, located on boulders on a sedimentary plateau at 70–80 m depth, was observed. The density ranged on average between 0.17 ± 0.04 and 0.8 ± 2.4 colonies m–2 with dense patches up to 8 colonies m–2. The population consisted primarily of many isolated single corallites and colonies of various sizes, some of which reached a maximum height of more than 40 cm. Deepwater fishing activities, primarily longline fishing, negatively affected this species. The newly collected data add knowledge about this vulnerable scleractinian coral. The documented negative effect of fishing activities on vulnerable marine ecosystem (VME) species further highlights the need for urgent conservation measures.

Contemporary Ichthyological and Fisheries Research of Deepwater Fish: New Advances, Current Challenges, and Future Developments

Deepwater fishes are a very diverse group of chondrichthyans and teleosts widely distributed in the world ocean from the Arctic to the Antarctic and inhabiting the water column and seabed of continental slopes, seamounts, and high seas usually at depths greater than 400 m [...]