Loss Of Fish Research Articles

Toxicity Responses of the Fish Behaviour and Morphological Changes at Chromium Chloride in Hetropneustes fossilis

The current aquatic studies of toxicity of chromium chloride depond on biotic or abiotic factors i.e. temperature, concentration of Metal Salt Oxidation, PH, values, alkalinity, salinity and hardness of water. The experimental fish caused external behaviour responses observed were rest lessens, jumping, erratic swimming, gulping of air at the surface, loss of equilibrium sluggishness, opercular movements and fishes lied on the water surface before death and morphological changes like, discoloration of skin pigmented patches on body, shedding of scales sedimentation of chemical on body, mucous secretion and ballooning were observed in exposed animals the observed data shown the H. fossilis can be used as a good bio-indicator for heavy metal contamination in fresh water bodies.

Regional species gains outpace losses across North American continental shelf regions

AbstractAimAlthough species richness globally is likely to be declining, patterns in diversity at the regional scale depend on species gains within new habitats and species losses from previously inhabited areas. Our understanding of the processes associated with gains or losses remains poor, including whether these events exhibit immediate or delayed responses to environmental change.LocationThe study focuses on nine temperate marine ecosystems in North America.Time periodThe study period varies by region, but overall encompasses observations from 1970 to 2014.Major taxa studiedWe identified regional gains and losses for 577 marine fish and invertebrate species.MethodsFrom a total of 166,213 sampling events from bottom trawls across North America that informed 17,997 independent observations of species gains and losses, we built generalized linear mixed effects models to test whether lagged temperature can explain instances of gains and losses of marine fishes and invertebrates in North American continental shelf habitats.ResultsWe found that gains were less likely in years with high seasonality, consistent with seasonal extremes as a strong constraint on species occurrence. Losses were also negatively associated with high seasonality, but the response was delayed by 3 years.Main conclusionsEnvironmental conditions play a role in species occupancy across diverse temperate marine ecosystems. Immediate gains paired with delayed losses can drive transient increases in species richness during times of environmental change. Identifying the dynamics behind regional species gains and losses is an important step towards prediction of biodiversity changes across ecosystems.

Fishing for hosts: Larval spurting by the endangered thick-shelled river mussel, Unio crassus.

Fishing for hosts: Larval spurting by the endangered thick-shelled river mussel, Unio crassus.

A dynamic dendritic connectivity assessment tool for the planning and design of barrier mitigation strategies in river networks

ContextIncreasing fragmentation of rivers caused by barriers continues to impact watersheds, especially disruption of fish migration patterns and loss of access to spawning and nursery habitats. Infrastructure expansion and ageing installations exacerbate the problem, reducing effectiveness of management in addressing barriers. Reduction in watershed connectivity requires effective tools capable of guiding river managers in remediation actions.ObjectivesOur objective was to develop a watershed dynamic connectivity assessment tool (D-CAT), a customizable geospatial tool capable of river analyses at varying watershed scales. The tool uses proven watershed connectivity modelling combined with an effective evaluation approach to provide measurable change model outcomes.MethodsThree different barrier encounter scenarios were examined using the D-CAT tool to study watershed connectivity. The tool was tested on a watershed area of the River Derwent, a major tributary of the River Trent system in the United Kingdom.ResultsFor each barrier scenario tested, the D-CAT tool indicated which barriers could be removed or modified to provide the greatest watershed connectivity improvement. The tool provided a prioritized list of barriers for each scenario under varying choices for the number of barriers to remove, demonstrating the utility of the D-CAT tool to planning and design.ConclusionsThe D-CAT tool is built to handle geographical data and variable user input, allowing in-depth watershed connectivity analysis. The tool forecasts the cumulative effects of alternative change scenarios for watershed connectivity, providing prioritization and optimization of removal strategies. The D-CAT tool offers significant support for landscape management towards better barrier removal/remediation decisions.

Epidemiology and economic impact of disease-related losses on commercial catfish farms: A seven-year case study from Alabama, USA

The objectives of this study were to determine statewide production losses caused by diseases, identify the most incident catfish diseases affecting Alabama (AL) farm-raised catfish production in freshwater ponds and their annual pattern, and determine disease-related economic impacts. The Alabama Fish Farming Center (AFFC) conducted seven annual retrospective questionnaire surveys of AL catfish farmers since 2015 to assess the epidemiological situation of farm-raised catfish fish diseases and their economic impacts. Across the study (2015–2021), the annual number of survey respondents ranged from 64 to 74, with a total of 482 respondents. The yearly survey response rate ranged from 95.6 to 100% (mean: 98.2%). The annual survey coverage area ranged from 6410 to 7006 ha/year. About 97% of survey coverage area reported fish losses caused by a disease. Fish diseases resulted in the loss of 9 million fish/year (2.9 million kg/year; 436.7 kg/ha/year). Bacterial diseases resulted in >83% of catfish disease losses (>5 times losses to non-bacterial causes). The most incident statewide catfish disease was hypervirulent Aeromonas hydrophila (225 kg/ha/year), followed by columnaris (140 kg/ha/year), followed by Edwardsiella (52 kg/ha/year). The temporal epidemiological analysis results indicate that annual trends of proliferative gill disease and Bolbophorus disease were correlated with prolonged precipitation periods and total quantity of rainfall, respectively. Economic losses caused by fish losses to bacterial diseases, non-bacterial diseases, production losses due to reduced feeding during outbreaks, and expenditures associated with catfish diseases were responsible for 54.5%, 10.8%, 22.0%, and 12.7% of total direct economic impacts attributed to AL farm-raised catfish industry, respectively. Total disease-related financial losses in west AL were 11.1 million USD/year (1651 USD/ha/year), representing about 9.5% of food-size catfish sales in AL. The present study provides the first extensive assessment of epidemiology and health economics of farm-raised catfish disease in the freshwater pond environment for a substantial duration. More studies focusing on disease losses at the county- and farm-level would provide useful information regarding the spatial epidemiology of diseases and their underlying risk factors.

Laboratory-based comparison of screening materials for excluding juvenile freshwater fishes from New Zealand water intakes

ABSTRACT Growing demand for water requires resource managers to be innovative to minimise impacts on aquatic ecosystems. There are increasing concerns about fish damage and losses at water intakes, but few studies have examined the effectiveness of different screening material for excluding New Zealand fishes. We experimentally tested six screens (50–100 and 100–200 mm rock bunds, 3 mm woven mesh, 1.5, 2 and 3 mm wedge-wire), on two introduced and five native fish species. Bluegill bully (> 32 mm), common bully (> 30 mm), Canterbury galaxias (> 47 mm) and rainbow trout (> 40 mm) were screened effectively by 3 mm woven mesh and wedge-wire. Chinook salmon (> 43 mm) and īnanga whitebait (> 46 mm) were excluded by 2 mm wedge-wire, but shortfin elvers (< 80 mm) penetrated 3 and 2 mm wedge-wire, and glass eels (< 63 mm) penetrated 1.5 mm wedge-wire. Rock bunds were effective barriers for rainbow trout but were ineffective, and acted as habitat, for bluegill bully, Canterbury galaxias and shortfin eels. We recommend that 1.5 mm wedge-wire screens are used in the tidal zone of New Zealand rivers, 2 mm screens are used beyond this zone with an upstream transition to 3 mm screens dependent on catchment-specific fisheries values.

Dispersal of aquatic and terrestrial organisms by waterbirds: A review of current knowledge and future priorities

Abstract We review progress in our understanding of the importance of waterbirds as dispersal vectors of other organisms, and identify priorities for further research. Waterbirds are excellent for long‐distance dispersal (LDD), whereas other vectors such as fish and mammals disperse similar propagules, but over shorter distances. Empirical studies of internal and external transport by waterbirds have shown that the former mechanism generally is more important. Internal transport is widely recognised for aquatic plants and aquatic invertebrates with resting eggs, but also is important for other organisms (e.g., terrestrial flowering plants not dispersed by frugivores, bryophytes, tardigrades, fish eggs). Waterbird vectors also are important in terrestrial habitats, and provide connectivity across terrestrial–aquatic boundaries. There are important differences in the roles of different waterbird species, especially those using different habitats along the aquatic–terrestrial gradient. Early attempts to predict zoochory based on propagule morphology have been found wanting, and more research is needed into how the traits of vectors and vectored organisms (including life history, dormancy and growth traits) explain dispersal interactions. Experimental studies have focused on the potential of propagules to survive internal or external transport, and research into factors determining the establishment success of propagules after dispersal is lacking. Recent spatially explicit models of seed dispersal by waterbirds should be expanded to include invertebrate dispersal, and to compare multiple bird species in the same landscape. Network approaches have been applied to plant–waterbird dispersal interactions, and these are needed for invertebrates. Genetic studies support effective LDD of plants and invertebrates along waterbird flyways, but there remains a lack of examples at a local scale. Next Generation Sequencing and genomics should be applied to waterbird‐mediated dispersal across the landscape. More studies of biogeography, community ecology, or population genetics should integrate waterbird movements at the design stage. Zoochory research has paid little attention to the dispersal of non‐pathogenic microbes (both eukaryotic and prokaryotic). Nevertheless, there is evidence that dispersal via avian guts can be central to the connectivity of aquatic microbial metacommunities. More work on microbial dispersal by waterbirds should explore its implications for biogeochemistry, and the interchange with gut flora of other aquatic organisms. In the Anthropocene, the role of migratory waterbirds in LDD of plants and other organisms is particularly important, for example in compensating for loss of large migratory mammals and fish, allowing native species to adjust their distributions under global warming, and spreading alien species along flyways after their initial introductions by human vectors. Recent technological advances have opened exciting opportunities that should be fully exploited to further our understanding of dispersal by waterbirds.

Effects of hook size and bait type on the size selectivity and short-time post-release mortality of a cyprinid fish (Cyprinus carpio L.) in recreational fisheries

A minimum legal length of 40 cm in recreational fisheries for the common carp (Cyprinus carpio) has been introduced in Türkiye and Czechia to prevent over-exploitation by anglers. This has resulted in more carp being released following capture, and possibly to increased losses of unharvested fish. This study was conducted to investigate the effect of hook size (4/0, 5/0, 6/0 & 7/0) and bait types (fish, corn kernels & dough) on the size of fish caught, catch rates, hooking location, dehooking time, bleeding (presence), and short-term post-release mortality. Angled fish were individually placed into a submerged cage for 1 h to monitor mortality. A total of 26 experimental fishing events, each event was divided into six angling sessions lasting 60 min each, were conducted at the Keban Dam Lake, Eastern Türkiye by three experienced anglers. Hook size influenced the size of captured fish but did not influence hooking location, dehooking time, bleeding (presence), and catch rates. Likewise, similar effects of bait type on hooking location, dehooking time, and bleeding (presence) were also recorded; however, in contrast to hook size, the bait type had a significant influence on fish catch rates and the catch efficiency of corn kernels was 2.1–3.4 times higher than the dough and fish baits. Furthermore, in contrast to the hook size, bait type had no significant influence on the size of fish caught. Smaller hook sizes were more likely to capture undersized fish, whereas larger hooks reduced the capture of undersized fish. Three out of 127 angled fish, caught by 4/0 and 5/0 hooks, experienced substantial bleeding and died within 1 h. The use of large hooks, e.g., > 5/0, is recommended to minimise the catch of undersized carp and mitigate hooking mortality.

Reducing the bycatch of undersized whiting (Merlangius merlangus) in flyshooting fisheries using a square mesh escape panel

Flyshooting or Scottish seining is a relatively new but fast growing seining technique. In the English Channel and the North Sea, the main targets are species without Total Allowable Catch (TAC), but whiting (Merlangius merlangus) is a quota-regulated species that is often landed as bycatch. This could make whiting a potential choke species under the current landing obligation. The goal of this study was to evaluate the effectivity of a square mesh panel (SMP) in releasing (undersized) whiting. A catch analysis was done to assess the loss of fish through the SMP. This revealed that over 40% of the undersized and 20% of the marketable whiting escaped through the SMP and was retained in the 55 mm SMP cover. The commercial loss of other species was limited to minor quantities of small red mullet (Mullus surmuletus). We conclude that this SMP can be an effective net adaptation to significantly reduce the bycatch of whiting in the flyshooting fishery with only a marginal commercial loss of other species.

Water users’ attitudes towards fish-protection screens: a case study from Australia’s Murray-Darling (Baaka) Basin

ABSTRACT Fish-protection screens for water pumps and channels can conserve fish populations and deliver operational benefits to irrigators. However, the uptake of fish screens is mixed, and there is limited evidence concerning irrigator attitudes towards this technology. The current study addresses this knowledge deficit through 26 semi-structured in-depth interviews with irrigators and other associated water users. The purpose of this study was to understand pump screening practices and experiences, the current level of awareness of fish-screening options, attitudes towards potential environmental and financial benefits, overall intentions to install fish screens, the role of attitudes and other factors in impacting these intentions, and critical fish screening knowledge gaps and communication preferences. Drawing on the theoretical framework of Diffusion of Innovations (DOI), the study identified that irrigators have low awareness of native fish loss and the benefits of fish screening. However, they are interested in learning more about the economic, social, and environmental benefits of fish screen adoption. Customised communications and education programs are needed to increase intentions to install fish screens in Australia.

Analysis of the transcriptomic profiles of Mandarin fish (Siniperca chuatsi) infected with red sea bream iridovirus (RSIV).

Red sea bream iridovirus (RSIV) belongs to the family Iridoviridae, genus Megalocytivirus, which could widely infect marine fish, causing diseases and huge economic losses. Now it has been reported that RSIV was also detected in diseased mandarin fish. Transmission electron microscopy and immunohistochemistry showed that spleen was the main target organ in mandarin fish infected with RSIV. To investigate the immune response mechanism of mandarin fish to RSIV infection, transcriptomics of RSIV-infected mandarin fish was analyzed. A total of 53,040 unigenes were obtained, and there were 21,576 and 17,904 unigenes had significant hit the Nr and SwissProt databases, respectively. In RSIV-infected and non-infected spleen tissues, there were 309 differentially expressed genes (DEGs), including 100 up-regulated genes and 209 down-regulated genes. Gene Ontology database (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways analysis were performed to reveal the function information and give a better understanding of the signal transduction pathways of DEGs. Further analysis of the cytokine-cytokine receptor interactions pathway exhibited that the expression of cytokines was widely activated after viral infection. In addition, ten DEGs were randomly selected and verified by quantitative real-time PCR, which revealed a similar expression tendency as the high-throughput sequencing data. These findings present valuable information that will benefit for better understanding of RSIV infection in mandarin fish.

Histopathological Assessment of Infested Farmed Clarias Gariepinus at Various Developmental Stages in Different Culture Management System

ABSTRACT: Parasitic infections infringe on different organs causing varying degrees of histological changes which contribute directly or indirectly to fish loss. Histological alterations play significant implication in fish health thereby proffer supports for effective diagnoses to improve the management of cultured fish. Various developmental stages of farmed Clarias gariepinus were randomly collected from 100 farms across the three agricultural zones (East, West and Far – East) in Lagos State, Nigeria from purposively classified culture systems based on water usage management systems (WUMS) into daily water renewal (DWR), weekly water renewal (WWR) and bi – weekly water renewal (BWR)). The organs (skin, gills and intestines) were selected for parasitological examinations and histological sectioning using standard procedure. The water qualities monitored were temperature, dissolved oxygen, pH, ammonia, nitrite, iron, alkalinity, hardness and turbidity and measured using standard methods. Descriptive statistics such as frequency count, percentages, standard deviation were used to determine the occurrence and rate of histological changes in relations with parasitic infections while semi-quantitative analysis was used to assess the histological lesion on gills. This study reveals possible relationship between parasitic infections and histological changes on the gills. The protozoans (Trichodina sp, Vorticella sp., Tetrahymena sp., Chilodonella sp., Piscinoodinium sp. and Ichthyobodo sp.) and monogenean trematode (Dactylogyrus sp., and Gyrodactylus sp.) were related parasites found with varying degrees of histological changes like hyperplasia of the epithelial cells, lifting of the primary epithelium, sloughing of the epithelium, fusion of the secondary lamellae, oedema of the lamellae, vacuolation of the epithelial cells, swelling of the epithelial cells, diffuse infiltration of lamina propria by neutrophil and necrosis of the secondary lamellae, classified into stages I, II and III. The most frequently observed histopathology in all the culture systems was hyperplasia of the gill lamellae; DWR-86.96%, WWR – 88.1%, BWR – 92.86%, followed by the fusion of the secondary lamellae; DWR-65.22%, WWR–75%, BWR– 78.57%. No histopathological change was observed on the skin and the intestine and lesions were least in the daily water renewal (DWR) culture system. Hence, it can be safely inferred that good management practice in terms of water renewal system should be encouraged to alleviate parasitic infections and minimize organ damage in cultured fish.

Glochidia Infection of Endemic Fishes from Lake Prespa, N. Macedonia

Large freshwater mussels (Unionida) are long-lived, have large bodies, and produce thousands to millions of larvae (glochidia) that usually must attach to host fish tissue to complete their life cycle. This is an obligate parasitic stage of mussel larvae. However, less than one in onemillion find a suitable host and survive. The degree of host specificity varies among unionid species, from specialists that can successfully parasitize only one or a few closely related fish species to generalists that can complete development on a taxonomically broad range of fish species. In addition, freshwater mussels are among the most threatened groups of animals. This is due to habitat destruction, the introduction of non-native species, and the loss of host fish on which their larvae (glochidia) are obligate parasites. Glochidiosis harms fish by affecting their growth; on the other hand, freshwater mussels play an important role in freshwaters by improving water quality and ridding the water of bacteria, algae, and pollutants, they are an indicator species of water quality. During our parasitological survey of fish from the Macedonian part of Lake Prespa in April 2022, many glochidia were found on the gills, skin, and fins of two endemic fishes, Prespa roach (Rutilus prespensis) and Prespa nase (Chondrostoma prespense), in the range of tens to thousands on one host. We thus recorded these two endemic species as new hosts of A. cygnea.

Climate tracking by freshwater fishes suggests that fish diversity in temperate lakes may be increasingly threatened by climate warming

AbstractAimMany freshwater fishes are migrating poleward to more thermally suitable habitats in response to warming climates. In this study, we aimed to identify which freshwater fishes are most sensitive to climatic changes and asked: (i) how fast are lakes warming? (ii) how fast are fishes moving? and (iii) are freshwater fishes tracking climate?LocationOntario, Canada.MethodsWe assembled a database containing time series data on climate and species occurrence data from 10,732 lakes between 1986 and 2017. We calculated the rate of lake warming and climate velocity for these lakes. Climate velocities were compared with biotic velocities, specifically the rate at which the northernmost extent of each species shifted north.ResultsLakes in Ontario warmed by 0.2°C decade−1 on average, at a climate velocity of 9.4 km decade−1 between 1986 and 2017. In response, some freshwater fishes have shifted their northern range boundaries with considerable interspecific variation ranging from species moving southwards at a rate of −58.9 km decade−1 to species ranges moving northwards at a rate of 83.6 km decade−1 over the same time period. More freshwater fish species are moving into northern lakes in Ontario than those being lost. Generally, predators are moving their range edges northwards, whereas prey fishes are being lost from northern lakes.Main ConclusionsThe concurrent loss of cooler refugia, combined with antagonistic competitive and predatory interactions with the range expanding species, has resulted in many commercially important predators moving their range edges northwards, whereas prey species have contracted their northern range edge boundaries. Trophic partitioning of range shifts highlights a previously undocumented observation of the loss of freshwater fishes from lower trophic levels in response to climate‐driven migrations.

Fish community assessment of shelf-edge artificial reefs along east-central Florida

Artificial reef development is a popular management tool used to enhance fish stocks, mitigate degradation or loss of natural habitats, and provide additional recreational opportunities. In Florida, artificial reef development is a top priority of the Florida Fish and Wildlife Division of Marine Fisheries Management’s Artificial Reef program; however, despite their popularity and support, our scientific understanding of how artificial reefs ecologically facilitate marine fisheries is limited in certain habitats. This is especially true of the many artificial reefs along Florida’s central east coast, which has received sporadic assessment over the past few decades. The objective of this study was to conduct a fishery-independent assessment of the reef fish communities inhabiting the artificial reef sites off central east coast Florida using a combination of vertical longline sampling (VLL) and baited remote underwater videos (BRUV). Red snapper (Lutjanus campechanus) and vermilion snapper (Rhomboplites aurorubens) had the largest catch-per-unit-effort (CPUE) during VLL sampling, with red snapper CPUE significantly greater on rubble artificial reefs deeper than 40 m and vermilion snapper CPUE significantly greater on artificial reefs shallower than 30 m. A total of 62 fish species were observed on BRUVs, and community analysis indicated that red snapper, vermilion snapper, and tomtate (Haemulon aurolineatum) contributed the most to differences in community composition. Red snapper had the greatest abundance on sites deeper than 40 m, while vermilion snapper and tomtates had greater abundance on sites shallower than 30 m; all three species were more abundant during summer. This study provides the first quantitative assessment of reef fish communities on artificial reefs along central east coast Florida. Further monitoring is encouraged to unravel possible interactive effects of reef type and other environmental factors on fish assemblages, although it is evident that the reefs sampled support multiple managed fisheries species.

Isolation and identification of Capillaria sp. in ornamental green terror (Andinoacara rivulatus Günther, 1860) farmed in Iran

Green terror (Andinoacara rivulatus) is one of the most popular freshwater ornamental fish of the Cichlidae, which is commonly bred and cultivated in Iran. The aim of this study was to investigate the main cause of green terror mass losses in an ornamental fish breeding center in Nazarabad, Alborz province. Following chronic and continuous losses of mature green terrors with clinical signs including white feces hanging from the anus, the fish were sampled between June 2021 and July 2021. The fish were packed in water-filled polyethylene bags and transported to the Ornamental Fish Clinic, Faculty of Veterinary Medicine, University of Tehran. In macroscopic examinations, cachexia and paleness of the fish were evident. In order to investigate ectoparasitic infestations, wet smears were prepared from skin and gills, and examined under a light microscope. However, no parasitic infection was observed. In addition, the fish were euthanised, necropsied, and internal organs such as the intestine were examined. Microscopic examination of the intestine showed a heavy infection with mature Capillaria sp. and the barrel-shaped eggs. In the present study, the severity of Capillaria infection was very high and determined to be the main cause of losses. In order to treat the other fish in the population, levamisole was administered for 48 h every 7 days for 28 days. After re-examination, fish losses completely stopped, and no infection was observed after 28 days.

Fish Losses of Euthynnus affinis Products at The Fish Landing Base Karangsong Indramayu, West Java

Euthynnus affinis is one of the most loved fish by the community. Fulfillment of the demand for tuna from the process of catching until it is landed for sale has the potential to experience a decrease in yield. The purpose of this study was to determine handling techniques, determine quality, and determine yield losses in tuna catches at the Karangsong Indramayu Fish Landing Base (PPI) West Java. The research was conducted by directly observing the handling process, observing the cold chain of tuna from unloading to loading, conducting organoleptic quality testing, ALT, TVB and calculating fish losses by referring to the Load Tracking (LT) method. The calculation of yield loss is carried out in three types, namely: physical loss, quality loss, and financial loss. The flow of the tuna handling process observed is the unloading process to the loading process. The value of the organoleptic quality test on tuna caught was 8, the ALT test value of the lowest average value was 16,000 col/g and the highest value was 35,000 col/g. The lowest average TVB test value was 9.96 mgN/100 g and the highest was 11.19 mgN/100 g. Euthynnus affinis from unloading to loading experienced physical, quality and financial losses of: 1.07%; 0.84%; and 2.05%.

Climate Disruption Caused by a Decline in Marine Biodiversity and Pollution

The world has focused on carbon mitigation as the only solution for climate change. This discussion paper considers how marine biodiversity regulates the climate, and the factors that control marine biodiversity.&#x0D; The main Greenhouse Gas (GHG) is water vapor, which accounts for 75% of all GHGs; the second most important is carbon dioxide, followed by methane and particulates such as black carbon (BC) soot. The concentration of water vapor in the atmosphere is regulated by air temperature; warmer conditions lead to higher evaporation, which in turn increases the concentration of water vapor, the Clausius-Clapeyron relation. This means that as the oceans and atmosphere warm, a self-reinforcing feedback loop accelerates the evaporation process to cause further warming.&#x0D; It is not considered possible to directly regulate atmospheric water vapor. This explains why climate change mitigation strategies have focussed primarily on reducing carbon dioxide emissions as the means to reduce water vapor. This report concludes that the current climate change mitigation strategy will not work on its own because it depends on decreasing the concentration of atmospheric carbon dioxide and on the assumption that water vapor is only regulated by temperature.&#x0D; 71% of planet Earth is covered by an ocean that has a surface microlayer (SML) between 1 µm and 1000µm deep, composed of lipids and surfactants produced by marine phytoplankton. This SML layer is known to promote the formation of aerosols and clouds; it also reduces the escape of water molecules and slows the transfer of thermal energy to the atmosphere. The concentration of water vapor is increasing in our atmosphere, and 100% of this increase is evaporation from the ocean surface; water vapour from land systems is decreasing. This means that the oceans are almost entirely responsible for climate change.&#x0D; The SML layer attracts toxic forever, lipophilic chemicals, microplastics and hydrophobic black carbon soot from the incomplete combustion of fossil fuels. Concentrations of toxic chemicals are 500 times higher in this SML layer than in the underlying water. Toxic forever chemicals combined with submicron and microplastic particles and black carbon particulates are known to be toxic to plankton. Marine primary productivity or phytoplankton photosynthesis may have declined by as much as 50% since the 1950s. Reduced phytoplankton plant growth equates to a degraded SML membrane, reduced carbon assimilation, and higher concentrations of dissolved carbon dioxide in ocean surface water, which accelerates the decline in ocean pH. The key phytoplankton species responsible for the production of the SML layer are the first to suffer from pH decline, a process called “ocean acidification”.&#x0D; Ocean acidification will lead to a regime shift away from the key carbonate-based species and diatoms below pH 7.95 which will be reached by 2045. The SML layer will decrease, allowing evaporation and atmospheric water vapor concentrations to increase. A reduced SML layer will lead to fewer aerosols, cloud formation and precipitation, as well as increased humidity and temperature. When clouds form under these conditions, the higher humidity will cause torrential downpours and flooding. The result could be catastrophic climate change, even if we achieve net zero by 2050. In parallel, ocean acidification and the collapse of the marine ecosystem could also lead to the loss of most seals, birds, whales, fish, and food supply for 3 billion people.

A catch limitation device to avoid excessive catches in the blue whiting (Micromesistius poutassou) Northeast Atlantic pelagic trawl fishery

Blue whiting (Micromesistius poutassou) is harvested in the Northeast Atlantic by a multinational fleet of pelagic trawlers. Occasionally, vessels take catches which exceed their remaining holding capacity and in extreme cases large catches cause codends to burst, resulting in spill of catch. To control catch quantity, a catch limitation system was developed and tested. The system consists of three components: 1) escape opening(s) in front of the codend to release excess fish, 2) a fish lock to prevent loss of fish through the escape opening(s) during haulback and at the surface, and 3) a choking unit to match codend capacity to the desired size of catch. Blue whiting escaped through both longitudinal slots and large (≥ 2 m) meshes in front of the codend. However, video observations showed that with large meshes in the upper panel, large amounts of blue whiting escaped long before the codend was full. Therefore, a design with large openings in the bottom was combined with longitudinal slots in the side and top panels. Two fish locks were tested: an oblique netting panel designed to seal off the codend when vessel speed reduce during haulback, and a cylinder of netting with a choking rope that closed it after the codend was filled. Both fish lock designs inhibited release of fish during haulback and at the surface, but the attachment of the constricting rope in the cylinder frequently broke. The choking unit consisted of a depth triggered releaser connected to a strap of rope wrapped around the codend. Mechanical releasers with factory-set depth trigger and electronic versions were tested. Both freed the choke point as intended, but occasionally at unpredictable depth. A reliable relationship (r2 = 0.94) was attained between codend choking position and catch amount, demonstrating that codend capacity could be adjusted to achieve target catch quantities. Our work shows that controlling catch quantity in the blue whiting pelagic trawl fishery can be achieved effectively through relatively simple modifications to the codend section Future work is needed to optimize the fish lock design and ensure the codend choking rope releasers trigger reliably and at the proper depth.

Introduction of non‐native fish for aquaculture in China: A systematic review

AbstractAquaculture, especially of non‐native species and translocated domestic species, is a greatly encouraged way of relieving the conflicts between food and economic demand and resource depletion. We herein summarized the introduction history of non‐native fish for aquacultural use in China, including 105 species introduced from abroad and 61 species translocated domestically across river basins, which has brought great economic benefits but high ecological risks. Of these, one‐fourth have successfully established wild populations in natural waters and 15% have successfully invaded. We presented specific examples of seven aquaculture species/taxa and three aquarium species/taxa to explain their outcomes. The notable economic benefits, complex species composition and strain selection of tilapias, carps and sturgeons may together facilitate their invasion, and result in fish diversity decline, genetic pollution, and loss of ecosystem service. We specifically reviewed invasion cases in lakes and reservoirs and found that lakes in western China and reservoirs made by major hydroprojects are hotspots for non‐native species, and this has led to the disappearance of endemic species and changes to the original faunal composition. The escaped non‐native fish introduced via aquaculture has changed the original fish biogeography, resulting in the loss of assemblage uniqueness and causing faunal homogeneity. China has achieved significant progress in completing the Aichi Targets by improving the legal system and strengthening conservational actions on controlling non‐native species. Further actions, especially on risk assessment and management of non‐native species are expected for a healthy outlook for the aquaculture industry of China.