Fishing Research Articles

The Effects of Water Temperature and Simulated Angling on the Physiological Stress Response of Largemouth Bass

AbstractThe Largemouth Bass Micropterus salmoides, a popular sport fish, is subjected to multiple sublethal stressors during angling, including high water temperature, exercise, handling, live‐well retention, and weigh‐in procedures. Combined effects of ambient and live‐well temperatures on the stress response and recovery from angling‐induced exercise have not been tested in conditions similar to those encountered in tournaments. Therefore, we assessed the effects of ambient temperature (17, 25, and 33°C) and live‐well temperature differential (−4, 0, and +4°C) on the physiological stress response of Largemouth Bass (mean length = 331 mm) at rest, following a simulated angling stressor, and throughout 8 h of recovery in live wells. Stress variables were measured in whole blood (hematocrit, hemoglobin, pH, partial pressure of oxygen [pO2], partial pressure of carbon dioxide [pCO2], Na+, K+, Ca2+, Cl−, and leukocytes) and plasma (cortisol, glucose, lactate, and osmolality). Fish acclimated to 17°C showed the greatest cortisol response after the chasing stressor; however, higher levels of glucose, lactate, pCO2, K+, and monocyte percentage were found at 33°C, and blood pH, Cl−, and lymphocyte percentage were lower at 33°C than at 17°C. When live‐well temperature was manipulated, cortisol levels were highest in fish subjected to the coldest conditions (acclimated to 17°C and retained in 13°C and 17°C live wells) and the warmest condition (acclimated to 33°C and retained in 37°C live wells). However, all fish subjected to the colder extremes survived, whereas 100% mortality occurred in the warmest condition. Besides cortisol, indicators of stress were less pronounced at colder temperatures. Glucose, lactate, and notably K+ concentrations were highest in 37°C live wells, and blood pH, Ca2+, Na+, and Cl− were lowest. Low blood lymphocytes and high monocytes at the warmest conditions indicate reduced immunocompetence or inflammation. Mortality at high temperature may result from exhaustion of aerobic and anaerobic energy sources, failure to recover from metabolic acidosis, and an inability to regain ionic balance.

Оценка ихтиофауны естественных и искусственных водоемов Нахичевани и влияющих на них факторов окружающей среды

The study is dedicated to the assessment of fish fauna of the natural and artificial water bodies in Nakhchivan in 2018–2022 and the environmental factors that have impact over them. It was determined for this period that fish fauna is distributed in 10 water bodies. Out of those water bodies, Nakhchivan reservoir dominates both from the perspective of species and fish hunting. Along with the study of fish fauna in aquifers, the factors influencing their development were also assessed. Although the balance is disturbed as a natural factor, factors such as industrial waste, garbage and solid waste, sewage waste, detergents and artificial fertilizers, agrochemicals, oil and oil products, radioactivity and thermal pollution are the main factors of environmental pollution. Other factors: untimely and excessive hunting, fishing during reproductive migration, the introduction of new fish species into freshwater sources, anthropogenic factors such as hydropower also have a significant impact on fish development.

Ontogenetic spatial dynamics of the deep-sea teleost Aphanopus carbo in the NE Atlantic according to otolith geochemistry

The spatial distribution of deep-sea fishes is commonly related to major water masses or regional circulatory features that in turn may reflect differences in food-web structure and productivity. Aphanopus carbo is a benthopelagic species that undergoes horizontal and vertical migrations driven by spawning and by feeding, and for which a large-scale clockwise migration around the NE Atlantic is hypothesized. In this work, the adequacy of otolith microchemical composition used as tool to discriminate A. carbo specimens caught at different areas was investigated. Furthermore, potential birth areas and spatial pattern migration throughout the species life cycle were studied. Trace element concentration (TEC) in the otolith edge allowed the discrimination of the locations where specimens were caught and supported the separation between the northern and the southern distribution areas. The existence of two natal sources was suggested based on the separation of otolith core TEC into two groups. Longitudinal multivariate analyses applied to TEC data also sustained the separation of the otoliths into two main groups, but the mixing between them gives support to the species migratory hypothesis. The acceptance of both southern and northern spawning grounds and of migratory movements along the NE Atlantic in both northward and southward directions implies changes to the current migratory hypothesis that might be translated into new definitions of A. carbo stock structure and therefore fisheries management.

Estimating Deep-Sea Fish Population Density From the Odour Extension Area: A Theoretical Basis and Comparison With the Conventional Methods

Accurately estimating the population density of deep-sea fish with a baited camera system has long been a significant challenge. Although several theoretical models have been developed using the first arrival time of an individual fish or time-varying fish abundance at the bait, none of the models allows for the spatio-temporal variability of the odour plume area extending from the bait. This study shows theoretically that the population density can be formulated as the inverse of the sample mean of the odour plume area extended until it reaches a first fish under the condition that fish at rest have a random dispersion. Each area estimate is governed by the homogeneous Poisson process and, hence, its probability density follows an exponential distribution. A large uncertainty can occur for each area estimate (sample), but the uncertainty decreases as the number of samples used to derive the sample mean increases by the law of large numbers. Numerical experiments conducted in the study indicate that the proposed method for inferring population density is also potentially applicable to cases in which the fish have a uniform or large-scale clumped dispersion. The experiments also show that the conventional method based on first arrival time fails to estimate the population density for any of the dispersion cases. This study also indicates that the reliability of the most popular inference method for estimating population density from the time-profile of fish abundance at the bait site was found to depend on the extension of the odour plume area and the dispersion pattern.

Comparison of Alfaxalone and Tricaine Methanesulfonate Immersion Anesthesia And Alfaxalone Residue Clearance In Rainbow Trout (Oncorhynchus Mykiss).

Alfaxalone, a synthetic neuroactive steroid, has been tested as an immersion anesthetic in ornamental fish, but its safety and efficacy in sport fish have not been investigated. In the current study, we compared the physiologic and behavioral effects of alfaxalone with those of tricaine methanesulfonate (MS222) for anesthesia of rainbow trout (Oncorhynchus mykiss) via water immersion. We also analyzed alfaxalone-exposed tissues to determine residue clearance times. Fish were anesthetized for 10 min by immersion in low-dose alfaxalone (Alow; 5 mg/L induction, 1 mg/L maintenance), high-dose alfaxalone (Ahigh; 5 mg/L induction, 2 mg/L maintenance), or MS222 (MS; 150 mg/L induction, 100 mg/L maintenance). Fish received all 3 treatments, separated by a washout period of at least 18 d in a blinded, complete crossover design. We hypothesized that immersion in Alow or Ahigh would provide a stable plane of anesthesia in rainbow trout, with dose-dependent time to recovery, and that opercular rates and depths of anesthesia would be equivalent to that of MS222. The time to anesthesia induction was longer for alfaxalone than MS222 but averaged less than 100 s. The time to recovery from anesthesia was also longer for alfaxalone than MS222, with significantly shorter recovery time for Alow than for Ahigh. All treatments decreased opercular rate and response to noxious stimuli. Alfaxalone residue clearance was greater than 80% from all tissues within 1 h, greater than 99% from muscle within 4 h, and 100% from all tissues within 36 h after exposure. We conclude that alfaxalone immersion at 5 mg/L for induction and 2 mg/L for maintenance provides a safe, viable alternative to MS222 for the anesthesia of rainbow trout.

Movement and habitat use by smallmouth bass Micropterus dolomieu velox in a dynamic Ozark Highlands riverscape.

Stream fish movement in response to changing resource availability and habitat needs is important for fish growth, survival and reproduction. The authors used radio telemetry to evaluate individual movements, daily movement rates, home ranges and habitat-use characteristics of adult (278-464 mm LT ) Neosho smallmouth bass Micropterus dolomieu velox in three Ozark Highlands streams from June 2016 to February 2018. The authors quantified variation in movement and habitat use among seasons and streams and examined relations with select environmental cues (i.e., temperature and discharge), fish size and sex. Maximum movement distances were an order of magnitude greater in the larger Elk River (17.0 km) and Buffalo Creek (12.9 km) than in the smaller Sycamore Creek (1.71 km), were similar in both upstream and downstream directions and typically occurred during the spring. Most movement rates were ≤10 m day-1 in all streams and seasons, except for Elk River during spring. Ranking of linear mixed-effects models using AICc supported that movement rates were much greater in spring and increased with stream size. Spring movement rate increased with discharge and water temperature; only weak relationships were apparent during other seasons. Increased variation in water temperature had a small negative effect on movement rate. Home range size was highly variable among individuals, ranging 45-15,061 m (median: 773 m), and was not related to fish size, sex, season or stream. Although some fish moved between rivers, this study's tagged fish did not use reservoir or associated interface habitat. Water temperatures used by this study's tagged fish followed seasonal patterns but indicated the use of thermal refugia during summer and winter. Deeper-water habitats were used in Buffalo Creek and in winter across all study streams, whereas greater velocities used in the Elk River likely reflect the increased use of run habitats. Use of pool habitats predominated among tagged fish, particularly in smaller streams. The results of this study indicate considerable heterogeneity in movement and habitat use within and among lotic populations of Neosho smallmouth bass. These findings suggest that population-specific management may be appropriate and highlight the importance of natural flow conditions (i.e., spring high flows) and connected habitats for this endemic sport fish, particularly in smaller streams.

The mixed phylogenetic origin of northern pike (Esox lucius Linnaeus 1758) populations in the Middle Danubian drainage

BackgroundPikes, members of genus Esox, are widespread freshwater predators of the northern hemisphere, and important sport fish also. From the Carpathian basin only one species, the northern pike (E. lucius) is noted. At the same time the pike stocks living in this area show high level of phenotypic variance (e.g. various body pattern) and its growth varies highly both among and within populations. These features usually explained by the environmental diversity of the area. Whereas we think that genetic reasons -e.g. the appearance of other/new pike species in the area- may also be responsible for these observed features. Since as no detailed information have been published from the pike populations of this area, so far; we conducted phylogenetic and morphological assay on 88 pike specimens, collected from 49 Middle Danubian sampling sites.ResultsOur phylogenetic surveys showed that the northern pike appear in the study area solely, but all the three of its major lineages (Northern, Circumpolar, Southern) were indicated. Only six specimens represent the Northern lineage, collected from the western part of the study area. The Circumpolar and Southern lineages were common in the Carpathian basin, but the Southern lineage showed higher levels of haplotype diversity than the Circumpolar clade. Which indicates that only the Southern lineage is native in the area, while the other two groups could have appeared in the Middle Danubian system either spontaneously or by human introduction. Moreover, the different clades appeared in the same populations, suggesting the opportunity of inter-lineage hybridisation. From the studied morphologicalal features, the number of scales on the lateral line and the head length showed significant differences among the lineages. At the same time the body pattern of the studied individuals seems to be rather influenced by the ontogenic changes than phylogeny.ConclusionsThe high phenotypic variability of Middle Danubian northern pike populations may be due that all of its three major clades appeared and came in secondary contact in the area. In the within watershed spread of the non-native lineages the human stocking/transfer may play a considerable role.

Integrating long‐term citizen science data and contemporary artisanal fishery survey data to investigate recreational and small‐scale shark fisheries in Kenya

Abstract Shark catches are common in small‐scale (artisanal) and recreational fisheries; the magnitudes of these catches remain poorly known and understudied, particularly in developing countries. Data from three sources were used to assess the composition of shark landings in these fisheries in Kenya: boat‐based recreational fishery tagging 1987–2016; observed landings from the Bycatch Assessment and Mitigation in the Western Indian Ocean Fisheries Project 2016–2017; and Catch Assessment Surveys landings data 2017–2020. Eighteen species were identified among 1,215 sharks recorded in small‐scale fisheries between June 2016 and June 2017. Most of them belonged to the families Carcharhinidae (26%), Triakidae (23%) and Sphyrnidae (14%). Longlines (41%), drift gillnets (30%) and bottom‐set gillnets (21%) recorded the highest proportions of catches. A total of 501 sharks comprising 16 species were recorded in the recreational tagging data between 1987 and 2016, caught using either trolling lines or rods and reels. The families Carcharhinidae (56%) and Sphyrnidae (12%) represented the highest proportion of the catch. A generalized linear model was used to assess the effect of year, gear type, season and vessel propulsion mode on the variation in catches of sharks in small‐scale fisheries between 2017 and 2020. Catches were significantly higher in 2017 with high catch rates observed in longlines and handlines. Findings from this study highlight the importance of citizen science by recreational fishers in increasing awareness around the risks and threats to shark populations. Strengthening of existing monitoring of shark interactions with small‐scale and recreational fisheries is important alongside the implementation of appropriate conservation and management measures such as reductions in fishing effort (e.g. prawn trawling) in nursery areas, prohibiting the capture of CITES‐protected species, and enforcing catch‐and‐release practices by sport fishers to ensure the long‐term sustainability of both the affected shark species and the livelihoods of the fishers.

Bathymetric Variation on the Quantitative Diversity in the Deep-sea Fish Assemblage of Southwest India, Arabian Sea

Bathymetric Variation on the Quantitative Diversity in the Deep-sea Fish Assemblage of Southwest India, Arabian Sea

Sustainable Livelihood Security in the Poyang Lake Eco-economic Zone: Ecologically Secure, Economically Efficient or Socially Equitable?

Sustainable Livelihood Security (SLS) remains a rarely considered yet important issue for rural sustainability and natural resource management. Particularly in China, rural SLS research in a typical area is urgently needed, but insufficient under the background of National Rural Revitalization and Ten-year Fishing Ban of Yangtze River. Focusing on the policy-targeted inland lake area, we proposed a Livelihood Security Analysis (LSA) framework by establishing an adaptive indicator system and integrating multiple econometrical and geographical methods. This study aims to evaluate the SLS in Poyang Lake Eco-economic Zone comprehensively from the three aspects of ecology, economy and society, analyze their spatial patterns, identify the main constraints, and finally give specific suggestions for improving rural sustainability management. The results showed that rural SLS in the inland great lake area tended to be vulnerable mainly due to the lagging economic efficiency and unbalanced social equality, and mediated by regional ecological characteristics. The overall SLS and Ecological Security Index (ESI) were higher in the north and lower in the south, while Economic Efficiency Index (EEI) and Social Equality Index (SEI) were at the middle level and circularly distributed around Nanchang City. The dominating factors which have greatly shaped the spatial pattern of SLS include rural per capita electricity consumption, fishery breeding area, population dependency ratio, urbanization rate, and fishery population. The obstacle degree is ranked as economic system > social system > ecological system. An outdated economy and incomplete social services are the main constraints, characterized by weak electricity consumption, limited beds in hospitals, low urbanization rate, deficient agricultural machinery power, and a small agricultural output value. Therefore, one urgent need is to activate the rural economy by reinforcing rural electric power facilities and promoting agricultural mechanization. In addition, transforming the peasants/fishermen to the non-agricultural sector should be accelerated, which will help to reduce ecological pressure, boost urban-rural integration and narrow the income gap.

Population genomic dynamics of mesopelagic lanternfishes Diaphus dumerilii, Lepidophanes guentheri, and Ceratoscopelus warmingii (Family: Myctophidae) in the Gulf of Mexico

Assessing the impacts of the Deepwater Horizon oil spill (DWHOS) on deep-sea fish assemblages of the Gulf of Mexico (GOM) has been hindered by an absence of baseline (pre-spill) data concerning the population genetic dynamics of these fishes. The lanternfishes (Myctophidae) are a speciose, yet understudied, taxonomic group, that comprise a significant portion of the global deep-sea biomass, making them integral members of meso- and bathy-pelagic food webs. Herein, we used a genomic approach (double digest restriction site associated DNA sequencing) to investigate the temporal genetic dynamics of three species of lanternfishes within the northern GOM in the region of the oil spill: Ceratoscopelus warmingii (N = 65, SNP = 1804), Diaphus dumerilii (N = 42, SNP = 2577), and Lepidophanes guentheri (N = 44, SNP = 3462). Fishes were sampled in 2011, and then again in 2015, and 2016, and genotyped using single nucleotide polymorphisms (SNP) markers. An additional 22 C. warmingii samples collected in 2014 from the western North Atlantic were used to assess genetic connectivity between these two regions. Overall, all three species were characterized by low levels of genetic diversity and high inbreeding coefficients, and within two of the three species (C. warmingii and L. guentheri), little (if any) evidence of population genetic structure was found within northern GOM waters. Conversely, significant intra-GOM genetic population structure was found for D. dumerilii, highlighting the need for a more robust population genetic survey of these fishes within the GOM to understand how populations of these fishes may respond to future environmental perturbations. In addition, significant genetic population structure was also found between sub-populations of C. warmingii from the northern GOM and western North Atlantic; with evidence of a mixture of two genetic populations co-occurring within the western North Atlantic. Given the potential for future environmental perturbations caused by expanding oil and gas extraction and climate change on GOM mesopelagic communities, rigorous population genetic assessments are required to understand the population dynamics of fishes and to safeguard the genetic diversity and resilience of this functionally important group of deep-sea fishes.

Inferring ecological strategies of Psenopsis spp. (Teleostei: Centrolophidae) inhabiting Indian waters from morphological features

ABSTRACT Morphology of the fish and otoliths are popularly used in the discrimination of species/stocks/populations and also to gather meaningful conclusions about their ecology. This approach is useful to enhance our understanding of the relationship between form and function in fishes when a direct assessment is impossible. Inter-species variation was analysed using geometric morphometric analysis for fish body shape, while morphometry and wavelet functions for sagittae morphology. A clear ecomorphological pattern in the body, as well as otolith shape, is evident among species as deeper inhabiting species possess a deeper body with oblong otoliths compared with shallower species that possess a more streamlined body with fusiform otoliths. We also observed that deeper species (P. obscura) possess bigger eyes for the optimum use of available light and bigger otoliths with higher otolith sensory area and otolith area ratio (S:O) for better sound reception capacities. Our hypothesis supports that the differences in fish morphological as well as sensorial traits (otoliths), which are closely related to their locomotion, foraging pattern and depth of habitation, lead to trophic segregation which in turn encourages their coexistence. This is the first work that discusses the relationship between body shape, otolith morphometry and morphology in deep-sea fishes and their ecomorphological interpretations. http://zoobank.org/lsid:zoobank.org:pub:663DD393-80B0-407D-907C-51E3F33ECCFB

MUSCULATURE AND NEUROTRANSMITTERS IN THE REPRODUCTIVE SYSTEM OF TREMATODES

The article analyzes own and published data concerning muscle elements present in various parts of the trematode reproductive system. The data on the presence of serotonergic and peptidergic (FMRFamidergic) nerve elements evidence the innervation of the trematode reproductive system departments by these neurotransmitters. The available literature information was supplemented by results of the study carried out on Prodistomum alaskense, a representative of the family Lepocreadiidae, an intestinal parasite of deep-sea fish (Zaprora silenus and Aptocyclus ventricosus). The localization of serotonergic and FMRFamidergic nerve structures was determined by immunocytochemistry. The musculature was stained using TRITC (tetramethylrhodamine-isothiocyanate) conjugated phalloidin. The slides were examined using a fluorescent microscope and a confocal laser scanning microscope. An analysis of the data and information in the literature suggest that the muscular system of the reproductive system is well developed in trematodes of various taxonomic groups and represented by circular, longitudinal, and, in some cases, by diagonal muscle fibers. The musculature of the trematode reproductive system is innervated by serotonergic and peptidergic (FMRFamidergic) neurons and their fibers which may be involved in regulating the contractile activity in various parts of the trematode reproductive system.

Comparación de cuatro métodos para contar peces en una bahía tropical: el caso del Área Marina de Manejo Bahía Santa Elena en el Pacífico de Costa Rica

Introduction: Tropical nature is experiencing an unprecedented threat that includes coastal fish communities that requires a close monitoring of species presence. The simultaneous use of several monitoring methods should reduce the bias caused by the selectivity of each method. Objective: This study used four different sampling methods over two years to assess and compare fish assemblages in the Santa Elena Bay Marine Management Area (AMM-BSE), North Pacific of Costa Rica. Methods: We examined changes in species richness and composition between upwelling and non-upwelling seasons from July 2019 and February 2020. We applied visual censuses, underwater remote cameras; bottom lines; and sport fishing. Results: We identified 140 species of fish (54 families); remote underwater cameras detected 83 %, followed by underwater visual censuses (65 %), sport-fishing (16 %) and bottom lines (14 %). Only the sport-fishing method detected differences in species richness and composition between seasons. Conclusion: Remote cameras appear to be the best method for species counts, and sport-fishing to detect seasonal differences in tropical coasts similar to the one studied here.

The impact of evolutionary trade-offs among bioluminescent organs and body shape in the deep sea: A case study on lanternfishes

Functional innovations play major roles in constraining or contributing to the evolutionary diversification of organismal morphology. Among fish key innovations, bioluminescence is critical to the success of many deep-sea fishes. Understanding evolutionary dynamics of deep-sea fish lineages and the role bioluminescent light organs have on their evolution is a continuing effort of many deep-sea biologists. This study focused on assessing how bioluminescent structures involved with sexual communication may be impacting the evolution of body shape in the lanternfishes (Myctophiformes), a lineage of fishes possessing some of the most extensive sexual dimorphism in bioluminescent structures seen in deep-sea organisms. Results from this study using geometric morphometrics integrated with a phylogenetic hypothesis of lanternfish relationships suggest there is significant evolutionary modularity between the caudal peduncle and the rest of the body within lanternfishes. Our results also show that most lanternfish species lacking caudal light organs cluster together in morphospace (Diaphus, Hintonia, Neoscopelidae), possess enlarged headlight organs (Diaphus), and exhibit lower phylogenetic signal than species possessing caudal light organs. These results support the hypothesis that lanternfish body-shape evolution is influenced by selective pressures on their light-producing tail organs and that the importance of caudal light organs in lanternfish communication may result in differential selection on the caudal area in species that possess them. One possible interpretation for why lanternfishes without caudal light organs coalesce in morphospace may be that by removing the caudal light organ, natural selection would select for a lanternfish caudal morphology optimized for the physical landscape of the midwater that they live in, favoring more energy efficient and slow sustained swimming styles.

Первые данные о макрозообентосе озера Тикшозеро

The article presents the results of the assessment and inventory of the current state of the macrozoobenthos communities of Lake Tikshozero (Western Karelia), which belongs to the small water bodies of the White Sea basin. The reservoir is remote from settlements and industrial facilities, it is used for recreation purposes, popular for amateur and sport fishing. There are given the results of studying the species diversity of macrozoobenthos, structure of dominant species, ratio of the main taxonomic groups, their quantitative indicators. The Tikshozero ecosystem is under the influence of human economic activity; a commercial trout farm is located in its water area. The work was carried out to assess the current state of the benthic fauna of a little-studied reservoir, which is in conditions of a transitional trophic status. The lake is part of the largest lake-river system of the Kem River in the republic and can act as 
 a model control object for studying the level of impact on small water bodies of the European North. Data on changes in the composition of benthic communities caused by various factors can serve as indicators of the aquatic environment. To preserve the current state of the Tikshozero ecosystem and to study the dynamics of possible changes it is necessary to conduct monitoring of the water body. Widespread indices were used to assess the degree of water quality by macrozoobenthos: chironomid index K, oligochaete index (Goodnight-Whitley), Mayer index (S). In accordance with the results obtained, the reservoir is reffered to moderately polluted water bodies. It has been established that by the level of development of macrozoobenthos and its structural and functional indicators the lake belongs to 
 α-mesotrophic water bodies. According to the value of the Pantle–Bukk saprobity index, the water body can be attributed to the β-mesosaprobic type (moderately polluted waters)

Microbiomes of Hadal Fishes across Trench Habitats Contain Similar Taxa and Known Piezophiles.

ABSTRACTHadal snailfishes are the deepest-living fishes in the ocean, inhabiting trenches from depths of ∼6,000 to 8,000 m. While the microbial communities in trench environments have begun to be characterized, the microbes associated with hadal megafauna remain relatively unknown. Here, we describe the gut microbiomes of two hadal snailfishes, Pseudoliparis swirei (Mariana Trench) and Notoliparis kermadecensis (Kermadec Trench), using 16S rRNA gene amplicon sequencing. We contextualize these microbiomes with comparisons to the abyssal macrourid Coryphaenoides yaquinae and the continental shelf-dwelling snailfish Careproctus melanurus. The microbial communities of the hadal snailfishes were distinct from their shallower counterparts and were dominated by the same sequences related to the Mycoplasmataceae and Desulfovibrionaceae. These shared taxa indicate that symbiont lineages have remained similar to the ancestral symbiont since their geographic separation or that they are dispersed between geographically distant trenches and subsequently colonize specific hosts. The abyssal and hadal fishes contained sequences related to known, cultured piezophiles, microbes that grow optimally under high hydrostatic pressure, including Psychromonas, Moritella, and Shewanella. These taxa are adept at colonizing nutrient-rich environments present in the deep ocean, such as on particles and in the guts of hosts, and we hypothesize they could make a dietary contribution to deep-sea fishes by degrading chitin and producing fatty acids. We characterize the gut microbiota within some of the deepest fishes to provide new insight into the diversity and distribution of host-associated microbial taxa and the potential of these animals, and the microbes they harbor, for understanding adaptation to deep-sea habitats.IMPORTANCE Hadal trenches, characterized by high hydrostatic pressures and low temperatures, are one of the most extreme environments on our planet. By examining the microbiome of abyssal and hadal fishes, we provide insight into the diversity and distribution of host-associated life at great depth. Our findings show that there are similar microbial populations in fishes geographically separated by thousands of miles, reflecting strong selection for specific microbial lineages. Only a few psychropiezophilic taxa, which do not reflect the diversity of microbial life at great depth, have been successfully isolated in the laboratory. Our examination of deep-sea fish microbiomes shows that typical high-pressure culturing methodologies, which have largely remained unchanged since the pioneering work of Claude ZoBell in the 1950s, may simulate the chemical environment found in animal guts and helps explain why the same deep-sea genera are consistently isolated.

Bioregionalization of the South Sandwich Islands through community analysis of bathyal fish and invertebrate assemblages using fishery-derived data

The South Sandwich Islands (SSI) are a volcanic archipelago in the Atlantic sector of the Southern Ocean; they are a biologically rich area, home to a range of benthic habitats such as hydrothermal vents and seamounts. A commercial longline fishery for two congeneric species of deep-sea fish, the Patagonian (Dissostichus eleginoides) and Antarctic (D. mawsoni) toothfish has been in operation annually at the SSI since 2005 and throughout its history has employed scientific observers to collect detailed information on the species caught during fishing operations. Previous studies have investigated the distributions and communities of benthic invertebrates, sampled via scientific cruises. Here we highlight the utility of demersal longlines as spatially extensive sampling tools to investigate both invertebrate and fish communities at the SSI. A clear gradient in the distribution of many fish and invertebrate species is evident across the latitudinal range of the archipelago, these distributions result in clear differences in fish communities between the north, mid, and south of the islands, whilst the invertebrate communities are less clearly delineated. Environmental variables were investigated as drivers in these communities, and seawater temperature appears to be a key abiotic factor in mediating the distributions of species and communities. As many of these communities are structured based on temperature dependent species distributions, it is likely climate change will alter these communities with poleward shifts in the ranges of many species.

Catch‐and‐Release Ice Fishing: Status, Issues, and Research Needs

AbstractCatch‐and‐release (C&R) ice fishing is a popular form of recreational angling. At present, there is a considerable deficiency in our understanding of how ice angling affects the physiology, behavior, and survival of fish. Thus, the purpose of this review was to summarize our current knowledge of the consequences of winter C&R fishing on fish biology and to identify key knowledge gaps. Our synthesis revealed that in addition to the typical stressors encountered from C&R fishing during the open‐water season, fish that are caught through the ice are subject to several unique challenges, including exposure to subzero air temperatures upon landing as well as unique gear types that are not commonly used in the summer (i.e., passive angling techniques). We currently understand that while C&R angling causes a generalized stress response, cold environments may mute or delay these effects and may also come with additional deleterious consequences, such as tissue freezing. Interestingly, reported mortality can be low following release but can be influenced by gear type, barotrauma, and hooking location. Postrelease behaviors and the spatial ecology of ice‐angled fish are poorly understood, but technologies such as telemetry and biologgers and an intensification of research on the topic are starting to produce new insights in this area. As it stands, research on the consequences of winter C&R angling is largely restricted to a handful of popular sport fish species, and these consequences are likely not being considered in management and conservation contexts. Given the increasing popularity of the sport, furthering our understanding of C&R impacts in the winter represents a timely and important area of inquiry and can be used to develop more informed and effective C&R guidelines and management practices.

Hemingway's Marlin and Pound's Canto 40

This essay focuses on an allusion to Hemingway's deep-sea fishing in Pound's Canto 40. The most direct source for Pound's allusion is probably Hemingway's letter to Pound dated 22 July 1933, in which he refers to his catching a world-record seven marlin in one day. Set in context, Pound's line about the record-setting, unnamed marlin fisherman groups him with monopolists who "extracted" natural resources such as oil for their private profits at the expense of the common good. Pound's reference in Canto 40 to Hemingway as a record-breaking marlin fisherman reflects tensions between the two writers that deepened in the 1930s.