Fish Avoidance Research Articles

Attraction and avoidance of wild demersal fish and crustaceans to open-net aquaculture pens resolved by baited and towed underwater camera surveys

Attraction and avoidance of wild demersal fish and crustaceans to open-net aquaculture pens resolved by baited and towed underwater camera surveys

Adult-onset asthma, allergy, and aspirin hypersensitivity associate with self-reported food avoidance

ABSTRACT Background The adoption of avoidance diets by adult-onset asthmatics has not previously been studied. We hypothesized that avoidance diets would associate with adult-onset asthma, allergy, and aspirin-exacerbated respiratory disease (AERD). Methods A total of 1247 subjects with adult-onset asthma (age range: 31–91) from the Finnish national registry, and age- and sex-matched controls (n = 1970) participated in a questionnaire study in 1997. We estimated the association between asthma/allergy/AERD and avoidance diets, adjusting for potential confounding factors and validated the results in two retrospective cohorts of 5080 rhinitis/rhinosinusitis patients and 167 AERD patients from 2019 to 2020. Results The presence of asthma positively associated with adoption of any avoidance diet (adjusted OR [CI95%] 1.24 [1.02–1.51], p = 0.029) as did allergic disease and self-reported AERD within the asthmatic group (1.79 [1.29–2.48], p = 0.001 and 1.69 [1.15–2.49], p = 0.007, respectively). Asthmatics and allergic asthmatics were more likely to report avoidance of fish, fruits and vegetables, and spices (p ≤ 0.03) compared to controls and non-allergic asthmatics. The adjusted OR for multiple diets among AERD patients was 2.57 [1.34–4.95] p = 0.005. In the validation, 26.2% of the allergic asthmatics and 10.8% of AERD patients had documented avoidance diets. Conclusions Our study shows a positive association between avoidance diets and adult-onset asthma, and with allergic disease or AERD within asthmatic patients. Although we lack information on the reason patients chose to observe a specific diet, our results reinforce the importance of asking patients about their diet and if needed, giving dietary advice for adult asthma patients to help them avoid the adoption of unnecessarily restrictive diets.

Quiet uncrewed surface vessels assess fish avoidance to motorized survey ships with varying noise levels in the Great Lakes

Acoustic surveys are a foundational component of many fisheries monitoring programs because they allow assessment of spatially extensive stocks. They are widely used to evaluate prey fish throughout the Great Lakes by numerous coordinating vessels. Traditionally, these surveys have been conducted by crewed and motorized vessels, but fish avoidance of motorized platforms has been reported in multiple studies and may bias survey estimates. Quiet uncrewed platforms are becoming increasingly available and offer the opportunity to explore bias in traditional surveys. Several identical quiet uncrewed surface vehicles (USVs) operated by Saildrone were equipped with 120 kHz Simrad EK80 transducers and deployed in Lakes Erie, Huron, Michigan, and Superior in the summers of 2021, 2022, and 2023. The USVs were overtaken by numerous motorized vessels over 2 km transects using transducers with the same frequency. Fishes showed a limited response to approaching vessels, and acoustic measures were similar between the USVs and motorized vessels. Therefore, acoustic surveys in the Great Lakes appear unbiased and are widely comparable. Findings from this work will inform interpretation of acoustic data in the Great Lakes and provide the largest scale testing of fish avoidance during acoustic surveys to date.

Quantifying conditional probabilities of fish-turbine encounters and impacts

Tidal turbines are one source of marine renewable energy but development of tidal power is hampered by uncertainties in fish-turbine interaction impacts. Current knowledge gaps exist in efforts to quantify risks, as empirical data and modeling studies have characterized components of fish approach and interaction with turbines, but a comprehensive model that quantifies conditional occurrence probabilities of fish approaching and then interacting with a turbine in sequential steps is lacking. We combined empirical acoustic density measurements of Pacific herring (Clupea pallasii) and when data limited, published probabilities in an impact probability model that includes approach, entrainment, interactions, and avoidance of fish with axial or cross-flow tidal turbines. Interaction impacts include fish collisions with stationary turbine components, blade strikes by rotating blades, and/or a collision followed by a blade strike. Impact probabilities for collision followed by a blade strike were lowest with estimates ranging from 0.0000242 to 0.0678, and highest for blade strike ranging from 0.000261 to 0.40. Maximum probabilities occurred for a cross-flow turbine at night with no active or passive avoidance. Estimates were lowest when probabilities were conditional on sequential events, and when active and passive avoidance was included for an axial-flow turbine during the day. As expected, conditional probabilities were typically lower than analogous independent events and literature values. Estimating impact probabilities for Pacific herring in Admiralty Inlet, Washington, United States for two device types illustrates utilization of existing data and simultaneously identifies data gaps needed to fully calculate empirical-based probabilities for any site-species combination.

Trajectory Tracking and Obstacle Avoidance of Robotic Fish Based on Nonlinear Model Predictive Control.

The attainment of accurate motion control for robotic fish inside intricate underwater environments continues to be a substantial obstacle within the realm of underwater robotics. This paper presents a proposed algorithm for trajectory tracking and obstacle avoidance planning in robotic fish, utilizing nonlinear model predictive control (NMPC). This methodology facilitates the implementation of optimization-based control in real-time, utilizing the present state and environmental data to effectively regulate the movements of the robotic fish with a high degree of agility. To begin with, a dynamic model of the robotic fish, incorporating accelerations, is formulated inside the framework of the world coordinate system. The last step involves providing a detailed explanation of the NMPC algorithm and developing obstacle avoidance and objective functions for the fish in water. This will enable the design of an NMPC controller that incorporates control restrictions. In order to assess the efficacy of the proposed approach, a comparative analysis is conducted between the NMPC algorithm and the pure pursuit (PP) algorithm in terms of trajectory tracking. This comparison serves to affirm the accuracy of the NMPC algorithm in effectively tracking trajectories. Moreover, a comparative analysis between the NMPC algorithm and the dynamic window approach (DWA) method in the context of obstacle avoidance planning highlights the superior resilience of the NMPC algorithm in this domain. The proposed strategy, which utilizes NMPC, demonstrates a viable alternative for achieving precise trajectory tracking and efficient obstacle avoidance planning in the context of robotic fish motion control within intricate surroundings. This method exhibits considerable potential for practical implementation and future application.

Fish avoidance of ships during acoustic surveys tested with quiet uncrewed surface vessels

Acoustic surveys to estimate fish biomass and abundance are a major component of many fisheries monitoring programs. An important bias in acoustic surveys is that fish may avoid the survey vessel. Here, we utilized quiet uncrewed surface vessels (USVs) equipped with 120 kHz split beam echosounders to evaluate fish responses to motorized survey vessels. Two of these USVs were deployed in Lakes Michigan and Huron in summer 2021 and compared against three motorized vessels used in conventional fisheries acoustic surveys. Paired comparisons employed vessel-drone passes that provided the opportunity to observe fish response as vessels approached and then overtook their quiet USV counterparts. Sound originating from the vessels was primarily in the 10–1000 Hz range. Overall received sound pressure levels for ships at the closest pass were 100 dB (re 1 µPa @ 1 m) for one and 133–134 dB for the other two vessels. In contrast, sound originating from the USV was not detectable over ambient noise. We examined acoustic data from the USVs for potential changes in total acoustic backscatter, average target depth, and average in situ target strength as vessels approached. We observed weak evidence of an avoidance response by fish to the vessel with the loudest noise profile and highest survey speed but not for the other two vessels. We also compared acoustic data from 33 2-km transects surveyed by both vessels and the USVs, finding few differences between vessel and USV data for water depths between 5 and 80 m. Results from this work suggest that acoustics estimates of fishes in Lakes Michigan and Huron (primarily alewife, rainbow smelt, and bloater) are largely consistent among the vessels used in these two lakes for standard acoustic surveys and that fish avoidance is minimal in water depths > 5 meters.

In Memoriam Professor Andrzej Orłowski (1947–2020)

Professor Andrzej Orlowski, a long-time employee of National Marine Fisheries Research Institute, passed away on October 27, 2020. He was an outstanding scientist in the field of hydroacoustics. Inventor of the method of use of multiple echo measurements to assess the type of the seabed. To this day, this method is called the Orlowski Method. Professor Orlowski was a member of the Physics Section of the SCOR, the NMFRI Scientific Council, the Polish Acoustical Society, ICES Fishery Acoustic Science and Technology Group, ICES Fish Technology and Fish Behavior Working Group, ICES SG Acoustic Seabed Classification and ICES SG Fish Avoidance of Research Vessels.

Ship noise quantification of fisheries vessels on the Great Lakes

Prey fish abundances in the Great Lakes are a driver for several agencies’ commitments to the Council of Lake Committees to support fisheries management. These management decisions have profound economic and social impacts within the Great Lakes region. Fisheries estimates done by echosounders or trawling may be biased due to the propagated noise from large fisheries vessels. In the first two years of a four-year collaborative study, crewed fisheries vessels and uncrewed Saildrone vessels were used to compare abundance estimates between “loud” and “quiet” vessels. To quantify the effects of ship noise on prey fish abundance estimates, a mobile ship noise measurement system was designed and deployed to measure radiated acoustic signatures of several ships in the Great Lakes. This talk will discuss the deployment of a mobile underwater acoustic test range and show results of ship noise measurements from the first two years of the program. In addition, plans for future data generation, analysis, and comparison between crewed and autonomous systems will be discussed and an overview of the effects of ship noise on fish avoidance will be discussed in the proceeding talk.

Quiet uncrewed surface vessel assesses fish avoidance of motorized survey ships in the Great Lakes

Acoustic surveys of fish are a foundational component of many fisheries monitoring programs, including surveys in the Great Lakes. These surveys are conducted with traditional crewed and motorized vessels, but fish avoidance of these types of platforms has been reported in multiple studies, potentially biasing estimates. A quiet uncrewed surface vessel, Saildrone, was equipped with a 120 kHz Simrad EK80 transducer and deployed in Lakes Huron, Michigan, and Superior in the summers of 2021 and 2022. The drone was then overtaken by numerous motorized vessels using transducers with the same frequency. The average target depth, target strength, and nautical area scattering during overtakes were compared. We looked for a fish behavioral response with General Additive Models using distance from the Saildrone to the vessel as the predictor. We also compared the effectiveness of acoustic surveys from each platform with analyses of variances over 2 km sections of the overtake. Fish showed a limited response to approaching vessels, and acoustic estimates of fisheries relevant measures were similar between Saildrone and motorized vessels. Findings from this work will inform interpretation of acoustic data in the Great Lakes and provide the largest scale testing of fish avoidance to acoustic surveys to date.

The fish paradox: people with low socio-economic status are not consuming the right type of fish

Abstract Background Fish intake is included in several national food-based dietary guidelines as a component of healthy diet because of its rich source of beneficial omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). However, heterogeneity among types of fish intake is rarely studied. We investigated the associations of socio-economic status (SES) with total and types of fish intake and validated whether types of fish intake was associated with plasma EPA and DHA. Methods From the Lifelines cohort study, 94 246 participants aged 44 ± 13 years old were included to test the association of two SES indicators, i.e., education level and income level, with dietary intakes of total, fatty, lean, fried, and other types of fish. Plasma EPA and DHA were measured in a minor subset of 575 participants (mean age: 50 ± 13 years old). Total and types of fish intake was assessed using Food Frequency Questionnaire. Linear regressions were applied, adjusted for relevant covariates. Results After adjusting for covariates, middle and low education were negatively associated with total, fatty, lean, and other fish intake (p < 0.001 for all), and positively associated with fried fish intake (β (SE): 0.04 (0.04), p < 0.001 for middle education; 0.07 (0.04), p < 0.001 for high education), with high education as the reference group. Similar results were observed for income level. In the subset population, total and fatty fish were positively associated with plasma EPA and DHA (p < 0.02 for all). Lean and other fish intake were positively associated with only DHA (p < 0.008 for all), but not EPA, while fried fish was not associated with either EPA or DHA in plasma (p > 0.1 for all). Conclusions Lower SES was associated with higher intake of fried fish, which did not seem to be associated with the fish-based EPA and DHA in plasma. Both nutrition education and food price policy could be implemented to increase the awareness and shape people's choice on types of fish. Key messages • People with low socio-economic status are consuming the type of fish that is not associated with fish-based omega-3 fatty acids, so nutrition education focusing on avoidance of fried fish is needed. • Food subsidy programs promoting intake and increasing affordability of healthier fish are needed to improve the nutritional awareness and status of our population.

Consumption and Preferences for Wild and Domestic Meat in Indigenous Communities in the Brazilian Atlantic Forest

Wild animals have traditionally been the main sources of protein available, if not the only, to numerous indigenous populations worldwide. However, greater access to markets, reduced availability or access to wildlife, and policies in support of agricultural development, have shifted food habits toward domestic and industrial sources of protein. In this study, we evaluated consumption patterns and preferences/avoidances for wild animals (wildmeat, crustaceans, and fish) in comparison to domestic sources of protein among the Potiguara living on the Brazilian coast. Using data from 843 semi-structured interviews applied to students from 28 indigenous villages, we found that domestic meats were more consumed and preferred as compared to wild animals (aquatic and game animals), despite the high abundance of fish and crustacean resources in the surveyed area. Consumption and preference for game were higher among male students while avoidance was higher among female students. The avoidance of domestic meats and fish was low for both genders. The occupation of the fathers affected students’ food habits, in those nature-related occupations (farmer, fisherman/woman, sugarcane worker) conditioned greater consumption of wildmeat and fish, while non-nature related occupations lead to greater consumption of protein from domestic sources. The consumption of protein from all sources increased with the distance between villages and a protected area. Our results indicate that the younger generation of Potiguaras does not regularly consume wildmeat and fish and their preference for domestic sources of protein is shaped by the socio-environmental context, access to different types of meat, and taste preferences.

Connections among Land Use, Water Quality, Biodiversity of Aquatic Invertebrates, and Fish Behavior in Amazon Rivers.

Rivers in the Amazon have among the greatest biodiversity in the world. The Xingu River, one of the tributaries of the Amazon River, has a length of 1640 km, draining 510,000 km2 in one of the most protected regions on the planet. The Middle Xingu region in Brazil has been highly impacted by mining and livestock farming, leading to habitat fragmentation due to altered water quality. Therefore, comparing two rivers (the preserved Xingu River and the impacted Fresco River) and their confluence, the aims of the present study were to (1) assess the land uses in the hydrographic basin; (2) determine the water quality by measurements of turbidity, total solids, and metals (Cd, Cu, Fe, Mn, Pb, Zn, and Hg); (3) compare the zooplankton biodiversity; and (4) to evaluate the avoidance behavior of fish (Astyanax bimaculatus) when exposed to waters from the Xingu and Fresco Rivers. Zooplankton were grouped and counted down to the family level. For the analysis of fish avoidance, a multi-compartment system was used. The forest class predominated at the study locations, accounting for 57.6%, 60.8%, and 63.9% of the total area at P1XR, P2FR, and P3XFR, respectively, although since 1985, at the same points, the forest had been reduced by 31.3%, 25.7%, and 27.9%. The Xingu River presented almost 300% more invertebrate families than the Fresco River, and the fish population preferred its waters (>50%). The inputs from the Fresco River impacted the water quality of the Xingu River, leading to reductions in local invertebrate biodiversity and potential habitats for fish in a typical case of habitat fragmentation due to anthropic factors.

Environmental DNA metabarcoding elucidates patterns of fish colonisation and co‐occurrences with amphibians in temperate wetlands created for biodiversity

Abstract Wetlands are biodiversity hotspots that provide several essential ecosystem services. On a global scale, wetlands have greatly declined due to human activities. To counteract wetland loss, created wetlands are used as a conservation tool to facilitate biodiversity and provide habitats mainly for birds and amphibians. Fishes are likely to colonise the created wetlands and potentially affect the diversity and occurrence of amphibians. Still, species occurrence data for fish in created wetlands are largely lacking. Using eDNA metabarcoding, we investigated occurrence and co‐occurrence patterns of fish and amphibian communities in 52 wetlands (some of which are ponds) created to benefit mainly bird and amphibian communities in south‐central Sweden. Altogether, 17 fish and five amphibian species were detected in the created wetlands out of the 32 fish and six amphibian species found in the regional species pool. Amphibians were less common in wetlands physically connected to other wetlands. Connected wetlands were more fish‐rich than isolated ones, suggesting potential fish avoidance. Additionally, the amphibian community occupied a narrower environmental niche compared to the fish community. Nevertheless, we observed only five statistically significant negative fish–amphibian species co‐occurrences (out of 14 species considered). Even though our results suggest amphibian avoidance/exclusion from the created biodiversity wetlands, they also show that fish and amphibians frequently co‐exist. Increased habitat heterogeneity in terms of water vegetation, size, shape, and structure of the wetland could be possible factors enabling the co‐existence of these two taxa. With this study, we contribute to the general knowledge of fish occurrence patterns in created biodiversity wetlands. By comparing the frequencies of fish occurrence in natural and created wetlands, we have shown that there was some mismatch in what is common in natural compared to created wetlands. This mismatch probably comes from species‐specific habitat requirements, stocking, and differences in detectability when using eDNA metabarcoding (small species detected) versus conventional multi‐mesh gill‐net methods (small species missed). Therefore, our results obtained using eDNA metabarcoding can complement the pre‐existing knowledge of amphibian and fish associations and increase our understanding of how to create wetlands to facilitate biodiversity of several taxa.

Phylogenetic signal found in fish–community response to an acoustic common carp deterrent

Abstract Non‐structural deterrents may limit invasive fish dispersal and range expansion without altering waterflow or navigation. Despite extensive research in laboratory and artificial environments, few studies have been conducted in situ and, of those, few have evaluated the full community response of fishes interacting with the deterrent. We deployed acoustic deterrents within a physical trap‐and‐sort fishway at Cootes Paradise, Ontario, Canada, to determine the avoidance responses of a community of fishes attempting to disperse into the wetland. To test the effectiveness of an acoustic deterrent, the catch rates of fishes entering Cootes Paradise were compared when the deterrent was off (control) and on (treatment). Community diversity was fit to candidate generalised linear models, and common carp catch abundance was fit to candidate generalised additive models, both of which were compared with backwards selection. The presence of a phylogenetic signal in fish responses was assessed with Pagel's λ and Blomberg's K indices of trait evolution. Over 11,500 fishes, representing 16 species and 12 families, were captured. The acoustic deterrent did not alter the Shannon diversity of fishes challenging the fishway, but a significant phylogenetic signal in species‐specific avoidance responses was observed. There was a modest decrease in the catch rates of common carp (ambient trials = 1.03 fish/hr, deterrent trials = 0.84 fish/hr), a species of major management concern. Fish avoidance responses to acoustic deterrents were widely variable, and species specific. The avoidance response of common carp, the target species, was weak, probably due to a complex acoustic environment surrounding the fishway. Group size did not alter deterrent efficacy, but precipitation, water temperature, and turbidity did. Our study successfully quantified acoustic deterrent responses across an entire community of wetland fishes, including both native and invasive species. We are the first to demonstrate that there is a phylogenetic component to deterrent responses across species. We also identify environmental parameters that alter deterrent efficacy in the field, and describe important considerations for the deployment of non‐structural deterrents in the field.

Underwater robots provide similar fish biodiversity assessments as divers on coral reefs

AbstractCoral reefs are under increasing threat, and the loss of reef‐associated fishes providing valuable ecosystem services is accelerating. The monitoring of such rapid changes has become a challenge for ecologists and ecosystems managers using traditional approaches like scuba divers performing underwater visual censuses (UVC) or diver operated video recording (DOV). However, the use of small, low‐cost robots could help tackle the challenge of such monitoring, provided that they perform at least as well as diver‐based methods. To address this question, tropical fish assemblages from 13 fringing reefs around Mayotte Island (Indian Ocean) were monitored along 50 m‐long transects using stereo videos recorded by a semi‐autonomous underwater vehicle (SAUV) and by a scuba diver (Diver Operated stereo Video system, DOV). Differences between the methods were tested for complementary fish assemblage metrics (species richness, total biomass, total density, Shannon diversity and Pielou evenness) and for the number and size of nine targeted species. SAUV recorded on average 35% higher biomass than DOV which in turn recorded on average 12% higher species richness. Biomass differences were found to be due to SAUV monitoring larger fishes than DOV, a potential marker of human‐related fish avoidance behaviour. This study demonstrates that SAUV provides accurate metrics of coral reef fish biodiversity compared to diver‐based procedures. Given their ability to conduct video transects at high frequency, 100 m depth range and at a moderate cost, SAUV is a promising tool for monitoring fish assemblages in coral reef ecosystems.

Effect of Processing on Fish Protein Antigenicity and Allergenicity.

Fish allergy is a life-long food allergy whose prevalence is affected by many demographic factors. Currently, there is no cure for fish allergy, which can only be managed by strict avoidance of fish in the diet. According to the WHO/IUIS Allergen Nomenclature Sub-Committee, 12 fish proteins are recognized as allergens. Different processing (thermal and non-thermal) techniques are applied to fish and fishery products to reduce microorganisms, extend shelf life, and alter organoleptic/nutritional properties. In this concise review, the development of a consistent terminology for studying food protein immunogenicity, antigenicity, and allergenicity is proposed. It also summarizes that food processing may lead to a decrease, no change, or even increase in fish antigenicity and allergenicity due to the change of protein solubility, protein denaturation, and the modification of linear or conformational epitopes. Recent studies investigated the effect of processing on fish antigenicity/allergenicity and were mainly conducted on commonly consumed fish species and major fish allergens using in vitro methods. Future research areas such as novel fish species/allergens and ex vivo/in vivo evaluation methods would convey a comprehensive view of the relationship between processing and fish allergy.

Influence of the presence of invasive mosquitofish and submerged vegetation on oviposition site selection by gray treefrogs (Hyla versicolor)

Amphibians often select oviposition sites based on a variety of cues that indicate the level of risk in the oviposition habitat. Surprisingly, the role of aquatic vegetation or habitat structure/complexity in anuran oviposition site selection has not been extensively studied even though it might affect perceived risk. We examined the effects of free-ranging invasive western mosquitofish (Gambusia affinis) and artificial vegetation/habitat structure on colonisation of experimental pools by gray treefrogs (Hyla versicolor). Hyla versicolor avoided ovipositing in mesocosms with G. affinis. The presence of artificial vegetation/habitat structure had no effect on oviposition site selection by H. versicolor, whether alone or in interaction with G. affinis. Our experiment provides evidence for the avoidance of fish, and more specifically G. affinis, by ovipositing H. versicolor; but provides no evidence for a role of vegetation/habitat structure.

Breeding stage, not sex, affects foraging characteristics in masked boobies at Rapa Nui

Sexual segregation in foraging occurs in some species and populations of boobies (Sulidae), but it is not a general pattern. Sexual segregation in foraging may occur to avoid competition for food, and this competition may intensify during specific stages of breeding. We examined sexual segregation in foraging in relation to breeding stage in masked boobies Sula dactylatra at Rapa Nui by tracking simultaneously incubating and chick-rearing birds using GPS recorders (n = 18) and collected a total of 11 regurgitate samples. Stable isotope analyses (δ13C and δ15N) of whole blood samples were carried out in 20 birds. There were no differences in foraging trip parameters or diet between females and males. Both sexes traveled farther and for longer while incubating than while rearing chicks. Isotopic niches (δ13C and δ15N) overlapped to some degree among all groups at all times, but the lowest overlap between sexes occurred during incubation. While preying on ephemerally distributed flying fish, vertical or horizontal competition avoidance may be almost impossible, and thus females and males share their foraging grounds. Since birds were tracked simultaneously, shorter foraging trips of chick-rearing birds must be an effect of the constraints of provisioning the chick. Differences observed in δ15N and δ13C values between sexes may be caused by subtle differences in their foraging behaviors, or by differences in physiology linked to breeding. Our findings suggest that local oceanography and its inherent food distribution are determinants for sexual segregation in foraging patterns in masked boobies and possibly also other booby species.Significance statementIn some animals, females and males forage on different areas or prey on different species to avoid competition for food resources. In boobies (Sula sp.), some studies show evidence of sexual segregation in foraging and others do not. Here, we tested if sexual segregation in foraging occurred in masked boobies on the Pacific island of Rapa Nui by studying simultaneously incubating and chick-rearing birds. We found no evidence of sexual segregation on foraging behavior or diet. We discuss that the difference between this and other studies in boobies may be an effect of the local prey availability. When the prey community is more diverse and heterogeneously distributed, each sex may access different resources and thus sexual foraging segregation will occur. In contrast, in areas like Rapa Nui where prey resources are distributed ephemerally, sexual segregation in foraging will not be useful and is thus less likely to occur.

Habenula kisspeptin retrieves morphine impaired fear memory in zebrafish

The habenula is an evolutionarily conserved brain structure, which has recently been implicated in fear memory. In the zebrafish, kisspeptin (Kiss1) is predominantly expressed in the habenula, which has been implicated as a modulator of fear response. Hence, in the present study, we questioned whether Kiss1 has a role in fear memory and morphine-induced fear memory impairment using an odorant cue (alarm substances, AS)-induced fear avoidance paradigm in adult zebrafish, whereby the fear-conditioned memory can be assessed by a change of basal place preference (= avoidance) of fish due to AS-induced fear experience. Subsequently, to examine the possible role of Kiss1 neurons-serotonergic pathway, kiss1 mRNA and serotonin levels were measured. AS exposure triggered fear episodes and fear-conditioned place avoidance. Morphine treatment followed by AS exposure, significantly impaired fear memory with increased time-spent in AS-paired compartment. However, fish administered with Kiss1 (10–21 mol/fish) after morphine treatment had significantly lower kiss1 mRNA levels but retained fear memory. In addition, the total brain serotonin levels were significantly increased in AS- and Kiss1-treated groups as compared to control and morphine treated group. These results suggest that habenular Kiss1 might be involved in consolidation or retrieval of fear memory through the serotonin system.

Behaviour and ability of a cyprinid (Schizopygopsis younghusbandi) to cope with accelerating flows when migrating downstream

AbstractThe migration corridors in regulated rivers lead downstream fish migrants, particularly juveniles to pass through water infrastructure. Accelerating flow, experienced by fish, might trigger avoidance behaviour and then influence the downstream migration efficacy. It is essential to understand the causes of avoidance behaviour exhibited by downstream migratory fish in accelerating flow. In this study, the effect of three different accelerating flows on the downstream migration behaviour of Schizopygopsis younghusbandi (S.Y) was investigated using a constriction wedge in a circulating flume. The results showed that some fish (30%, 23%, and 39% under low, medium, and high flow conditions, respectively) repeatedly attempted to burst upstream with positive rheotaxis prior to successful passage downstream. Under the low‐, medium‐, and high‐accelerating levels, the average fish swimming speeds were 89.19, 91.28, and 111.94 cm/s, respectively; these values were close to the critical swimming speed (110.42 cm/s) of the target fish. The water velocities at the fish avoidance points were centrally distributed at approximately 73.03 cm/s. Regarding turbulence, the results exhibited that the S.Y generally responded to a discrete range of <50 cm2/s2 of turbulent kinetic energy and < 2 N/m2 of the horizontal component of the Reynolds shear stress (RSSxy). Also, the fish that exhibited avoidance behaviour were not centrally distributed in the lateral and longitudinal velocity locations, where there was an abrupt change in the gradient. This study highlighted the impact of accelerating flow on the downstream fish migration behaviour of a cyprinid. Furthermore, this study quantified the hydraulic factors that triggered this avoidance. Thus, it provided experimental support for optimizing the design of the hydraulic factors for downstream fishways.