Fish Movement Research Articles

Consequences of Juvenile Fish Movement and Seascape Connectivity: Does the Concept of Nursery Habitat Need a Rethink?

Estuarine and adjacent inshore habitats have long been recognised as important nursery areas for fishes before they disperse to coastal habitats. Assessing nursery function supports spatial and fisheries management, yet work commonly focusses on singular habitat types. Re-considering how juvenile fish connect habitats may improve our understanding of nursery function and the scales that recruits are supplied to coastal fisheries. This study quantified the juvenile movements of two harvested fishes in south-eastern Australia, luderick (Girella tricuspidata) and yellowfin bream (Acanthopagrus australis). Acoustic tags were used to track 33 luderick and 20 yellowfin bream from seagrass meadows for up to ~400 days in Jervis Bay Marine Park. Both species had relatively small home ranges (< 7 km2) and exhibited site attachment to seagrass meadows where they were released. Most luderick and yellowfin bream were detected moving 100’s metres to kilometres to reefs adjacent to seagrass, although these movements were not habitat shifts. Rather, reef-ward movements represented repeated visits that lasted days to months before fish returned to seagrass, suggesting that these movements may be explorations in search of suitable adult habitat. Strong retention within an existing marine reserve was observed, with only five of 33 fish tagged within reserves crossing the boundary into fished waters. Overall, our results demonstrate that juvenile fish use and connect multiple habitat types during their movements. These findings support the broadening of the nursery concept from single habitats to a mosaic of functionally connected habitat patches (dubbed ‘seascape nurseries’).

Recovery of a Population of Slimy Sculpin (Uranidea cognata) after an Autumn Fish Kill in the Headwaters of a Minnesota Trout Stream

Toxic runoff from heavy rains on 26 September 2019 caused a complete fish kill on the 2 km long headwater reach of Garvin Brook, Winona County, Minnesota, USA. This project examined the recovery of the slimy sculpin (Uranidea cognata) population within the lower 900 m of the kill zone, comparing relative abundance estimates and size structures between the kill zone and a downstream, unimpacted reference section. Electrofishing surveys were conducted at 24 sites (12 within both kill and reference zones) at 6, 11, 18, 28, and 42 months post-kill to assess relative abundance (catch-per-effort (CPE), fish/min) and population age structures (based on total length). At six months post-kill, sculpin were present throughout the kill zone. However, adult CPE declined significantly with upstream distance, which was suggestive of the ongoing immigration of adult sculpin from downstream. Age structures were similar in kill and reference zones with all size/age groups present in both zones after six months, while CPE was twice as high in the reference (6.3 fish/min) versus the kill zone (3.0 fish/min). After 11 months, CPE did not differ between zones (14 fish/min) and remained that way for the remainder of the study. However, age structures differed dramatically between zones at both 11 and 18 months post-kill; adult sculpin were significantly more abundant in the reference zone, whereas juvenile fish dominated the kill zone. By 28 months post-kill, both sculpin abundance and age structure within the kill zone had fully recovered from the kill. Sculpin recovery was accomplished mostly through enhanced reproduction within the kill zone following initial post-kill movements of both adult and juvenile fish into the kill zone from downstream. Low predation on juvenile sculpin due to a reduced abundance of trout and adult sculpin post-kill likely allowed more rapid recovery of the sculpin population within the kill zone.

Freshwater fish otoliths record signals from both water and physiological processes: new insights from Sr/Ca and Ba/Ca ratios

Using strontium (Sr) and barium (Ba) in otoliths to determine natal origins and understand patterns of fish movements is based on the fundamental assumption that otoliths record water chemistry signals without any major alterations. Although prior studies highlighted that fish physiology can modify the water signal in otoliths, studies for freshwater fish are scarce. We exposed different groups of Atlantic salmon parr Salmo salar to different scenarios of ambient-level variations in Sr/Ca and Ba/Ca ratios and then combined otolith chemical profiles with environmental data (water chemistry and temperature), Fulton's index, and otolith growth rates to assess what factors explain/influence the elemental ratios of Sr and Ba in otoliths. Generalized additive mixed models (GAMMs) using water-based otolith composition, temperature, Fulton's index, and “individual” as explanatory variables allow to demonstrate that water chemistry alone cannot fully explain measured ratios in otoliths, except in scenarios involving significant changes in water chemistry. Other factors (physiological effects) should be accounted for reproducing short and minimal seasonal variations in water composition, considering that inter-individual variability contributes quite significantly in most scenarios.

Navigating the drought: upstream migration of a small-sized Cypriniformes (Telestes muticellus) in response to drying in a partially intermittent mountain stream

River flow intermittence is a natural phenomenon intensified by human activities, such as water abstraction and the effects of climate change. A growing number of rivers are predicted to experience intermittent flows, which may impact the diversity and abundance of freshwater species. Dry riverbeds directly diminish the availability of habitats for freshwater organisms, and suitable environments can turn into ecological traps with reduced survival rates, posing a significant threat to population persistence. Even though fish movements can enable drought-affected populations to persist, little is known about individual fish movement between intermittent and perennial reaches. Here, we study the movement of individual PIT-tagged Italian riffle dace (Telestes muticellus) in an intermittent and perennial river reach before, during and after two severe drying events. A high proportion of fish from the intermittent reach survived the drying riverbed through directed upstream migration. This was manifested in fish living in the intermittent reach of the river displaying significantly higher linear ranges, and net travelled distances during the monitoring period than fish in the perennial reach, which remained resident with limited linear range and net distances travelled. This finding underscores the importance of conserving longitudinal river connectivity in the face of increased water scarcity and intermittent flow patterns.

Encapsulated stretchable amphibious strain sensors.

Soft and stretchable strain sensors have found wide applications in health monitoring, motion tracking, and robotic sensing. There is a growing demand for strain sensors in amphibious environments, such as implantable sensors, wearable sensors for swimmers/divers, and underwater robotic sensors. However, developing a sensitive, stretchable, and robust amphibious strain sensor remains challenging. This work presents an encapsulated stretchable amphibious strain sensor. The conductive layer, made of silver nanowires embedded below the surface of polydimethylsiloxane, was sandwiched by two layers of thermoplastic polyurethane. Periodic sharp cuts were introduced to change the direction of flow from across the sensor to along the conductive path defined by the opening cracks. The crack advancing and opening is controlled by a unique combination of weak/strong interfaces within the sandwich structure. The cut design and the interfacial interactions between the layers were investigated. The strain sensor exhibited a high gauge factor up to 289, a linear sensing response, a fast response time (53 ms), excellent robustness against over-strain, and stability after 16 000 loading cycles and 20 days in an aqueous saline solution. The functionality of this amphibious strain sensor was demonstrated by tracking the motion of a robotic fish, undertaking language recognition underwater, and monitoring the blood pressure of a porcine aorta. This illustrates the promising potential for this strain sensor for both underwater use and surgically implantable applications.

Epigenetic and physiological alterations in zebrafish subjected to hypergravity.

Gravity is one of the most constant environmental factors across Earth's evolution and all organisms are adapted to it. Consequently, spatial exploration has captured the interest in studying the biological changes that physiological alterations are caused by gravity. In the last two decades, epigenetics has explained how environmental cues can alter gene functions in organisms. Although many studies addressed gravity, the underlying biological and molecular mechanisms that occur in altered gravity for those epigenetics-related mechanisms, are mostly inexistent. The present study addressed the effects of hypergravity on development, behavior, gene expression, and most importantly, on the epigenetic changes in a worldwide animal model, the zebrafish (Danio rerio). To perform hypergravity experiments, a custom-centrifuge simulating the large diameter centrifuge (100 rpm ~ 3 g) was designed and zebrafish embryos were exposed during 5 days post fertilization (dpf). Results showed a significant decrease in survival at 2 dpf but no significance in the hatching rate. Physiological and morphological alterations including fish position, movement frequency, and swimming behavior showed significant changes due to hypergravity. Epigenetic studies showed significant hypermethylation of the genome of the zebrafish larvae subjected to 5 days of hypergravity. Downregulation of the gene expression of three epigenetic-related genes (dnmt1, dnmt3, and tet1), although not significant, was further observed. Taken altogether, gravity alterations affected biological responses including epigenetics in fish, providing a valuable roadmap of the putative hazards of living beyond Earth.

Variant proposal of the fish passage using technical and close to nature approach

Passing barriers on streams is nowadays an important activity for the protection and restoration of water ecosystems, and one of the goals of the European Union in the field of water habitat protection, that means barriers on waterways should be made suitable for the migration of aquatic fauna. The design and hydraulic parameters of these structures are fundamental in their design process, determining the effectiveness of fish passes in facilitating safe and efficient fish migration. These parameters should consider the specific needs and behaviours of the target fish species. It should provide suitable water depths, velocities, and facilitate fish movement upstream or downstream. The choice between technical fish passes, such as slot pass, and nature-like ones, such as rock ramps, is crucial. The selection of the right type also depends on various factors including the topography, hydrology and the species of fish being targeted. However, it is easier to achieve the parameters by technical fish pass. The proposed fish pass and its parameters were simulated by 1D mathematical model HEC-RAS. It was very difficult to design and fulfil all parameters according to the legislation. For more accurate results is recommended use of 2D or 3D models, or physical models.

An individual-based model to predict the spatial distribution of northern pike, European perch and pikeperch from habitat use in a reservoir subject to water level fluctuations

Reservoirs are subject to artificial water level fluctuations leading to a degradation of the littoral habitats. This often results in reduced productivity and biological diversity, particularly for fish. The development of predictive tools of fish population dynamics linked to habitat characteristics can help to optimize management actions such as habitat restoration. We developed a spatially explicit individual-based model, the 3Plake model, which predicts the spatial distribution of three fish species, northern pike, European perch and pikeperch, over seasons and diel cycles according to their habitat use. The model was calibrated with an accurate description of habitat and high spatial and temporal resolution data of fish movements in a French reservoir. The model calibration is only based on a species-specific coefficient of habitat selectivity. It was chosen to (i) match the observed and simulated traveled hourly and daily distances and (ii) minimize a metric quantifying the distance between observed and simulated density maps. The 3Plake model correctly simulated the means of traveled distances and the species distributions along the year on the study reservoir. The minimal input required (HSI maps and maximum distance range) allows its easy implementation on other reservoirs and fish species. It could be used to assess the impact of habitat restoration or water level management scenarios on fish distribution.

Artificial light at night affects fish passage rates in two small‐sized Cypriniformes fish

AbstractAn increasing presence of instream structures such as weirs, dams, culverts and reservoirs degrades habitats, fragments rivers and blocks fish movements worldwide. Longitudinal river movements are fundamental for many fish species and the most widespread solution to restore longitudinal connectivity is the implementation of different fish passage solutions. Fishway functionality, however, is highly variable. To design a functional fishway, several aspects of the fish's interaction with its environment need to be taken into consideration. Artificial light at night (ALAN) can affect a range of different behaviours in fish, from activity and movement to feeding and predator–prey relationships. In a fish passage setting, fish are exposed to artificial light at night (ALAN) in the form of light pollution, but, sometimes, also as part of the fish passage solution. Although likely highly species specific, the effect of artificial light on fish passage behaviour has been little explored. Here we study the passage behaviour of two small‐sized fish species, European gudgeon (Gobio gobio) and Italian riffle dace (Telestes muticellus), over a scaled deep side notch weir in a hydraulic flume in three different light conditions: daylight, darkness and ALAN. Although both species passed the obstacle at high efficiencies under all light conditions, their passage behaviours were influenced by light, particularly at the higher levels. While ALAN reduced passage success and resulted in delayed passage for gudgeon, riffle dace passed at higher rates under the artificial light compared to night treatment. Both results indicate a risk of negative effects from ALAN on passage performance at real fishways—or movement rates in lit areas of natural streams—for both species. Independent of light conditions, individuals of both species also passed faster after repeated trials, demonstrating learning in a fish passage context.

Meta-analysis of 87Sr/86Sr ratios in otoliths to establish thresholds for determining fish movement

Unpublished data were combined with a literature review to test a hypothesis of whether there is a pattern for classifying fish as “movers” or “residents” according to variability in strontium isotope ( 87 Sr/ 86 Sr) ratios in otoliths as a function of its environmental fingerprint. The variability in Sr ratios found in the otoliths of fish specimens as a percentage of isotopic environmental variability was used to determine the intensity of movement in a given study area (POEVSri index). A classic meta-analysis and a frequentist regression were applied to obtain a logistic model to describe the pattern. The meta-analysis returned a POEVSri limit of 28.95% for sedentary individuals and the logistic model shows a high probability of movement for POEVSri indices over 32%. There is a gradient of movement probabilities in the POEVSri interval from 8 to 32%, with each class having equal odds when POEVSri is approximately 20%. Regarding applicability for future studies, if aspects such as sufficient spatial and seasonal water sampling are addressed, the model provides two different thresholds for fish: a priori “movers” are those with POEVSri ≥ 32%, and resident fish have POEVSri ≤ 8%.

Movement of Paddlefish once past a lock‐and‐dam structure on the Alabama River

AbstractObjectiveMovement of fish past dams can be facilitated by dedicated fish passage structures, navigational locks, and crested spillways, with the efficacy of a passage structure depending strongly on the nature of the system (height of the dam, flow rate, etc.) and the fish's behavior and swimming capability. However, once the fish have passed a dam, whether by using a mitigation structure or due to active translocation, they encounter a different habitat upstream versus in the tailrace, potentially affecting their ability to continue their upstream migration.MethodsHere, we had two objectives. First, we determined whether Paddlefish Polyodon spathula that successfully passed a structure continued their upstream migration in the Alabama River. Because assuring passage by tagged fish required that we move the fish past the dam, our second objective was to determine whether translocated fish exhibited fallback behavior (downstream drift or movement postrelease that would compromise their continued migration). We used both active and passive telemetry methods to quantify the postpassage movements of tagged and translocated Paddlefish.ResultFish that were translocated above Claiborne Lock and Dam (CLD) exhibited upriver movements once translocated, and they exhibited no fallback (i.e., downstream movement with delayed or no continuation upstream). Timing of movement relative to spawning periods did not influence initial fish movement or the likelihood of reaching the next upstream dam (Millers Ferry Lock and Dam [MFLD]; ~100 river kilometers upstream) within the first 30 days of observation, but more fish that were tagged and released during the early prespawn period made it to within 4.83 km of MFLD (the location of our closest receiver below MFLD) relative to fish from the prespawn or spawning period. Fish that were released above CLD had a lower probability of being subsequently detected downstream of their release sites compared to fish that were released below CLD.ConclusionOur findings support that Paddlefish will continue their upstream migration once they have passed a structure, despite changes in habitat.

Behavior Patterns of Betch Fish (Betta sp.) Towards Different Lamp Light Colors

Betta fish (Betta sp.) is a type of ornamental fish that has unique characteristics compared to other ornamental fish. This research was carried out in November 2023 with the aim of finding out the behavioral patterns of Betta fish when exposed to different types of light. This research used a quantitative method with a (RAL). The results of the research showed that there were changes in behavior in Betta fish (Betta sp.) that had been given different colored lights. The reason why fish are attracted to light is, among other things, because fish have positive phototaxis properties which cause fish to be stimulated and attracted to gather at light sources. In this research, it can be seen that the movement of betta fish moves away from the light source, because the light coming out of the lamp will become hot if it is turned on for too long. If this goes on for a long time, it is feared that the fish will become bored and also experience stress.

Analysis of Sea Surface Temperature and Chlorophyll-A and Its Relationship with Catch Results Flying Fish Eggs in the Waters of the Kei Islands

The Kei Islands water area is quite productive in fisheries management. Environmental characteristics and oceanographic factors in a body of water will determine the potential of fisheries resources in a water body, and influence fish movement patterns and the formation of fishing areas for flying fish eggs. This research aims to examine the distribution of sea surface temperature and chlorophyll-a concentrations and analyze the relationship between sea surface temperature and chlorophyll-a concentrations with catches of flying fish eggs. The research focused on the waters of the Kei Islands, Southeast Maluku, which is an area for catching flying fish eggs. The research data was studied in the period December 2014 – November 2017. SPL and Chlorophyll-a data were downloaded from Citra MODIS-Aqua, while data on flying fish egg production was obtained from PPN Tual. The research results show that the monthly average SST distribution is between 25.03-30.42ºC, and the monthly average of chlorophyll-a varies quite widely with a range of 0.05-3.09 mg/m3. The number of flying fish egg production fluctuates every year with a production range of 36.28-81.905 kg. The peak of catching flying fish eggs occurs in June-September (eastern season and transition season II). The results of the analysis show that the correlation between SST and chlorophyll-a variables has a very dominant influence on the abundance of flying fish eggs.

Development of the bioinspired propulsion system for a robotic fish

Biomimetic robots aim to replicate the movement principles of living creatures, which have been continuously perfected by nature to ensure survival. Technically, survival comprises two factors: optimizing movement efficacy, such as speed, distance traveled, or acceleration, and minimizing energy consumption during movement. Researchers have made several attempts to develop a biomimetic fish robot [1–3]. Tunas are a group of fish with numerous evolutionary adaptations that make them exceptional swimmers, including tail shape, lateral peduncle keels, pectoral fin shape, and finlets. Thunniform locomotion is characterized by limited undulation, typically restricted to the rear one-third of the body, with maximal amplitude reached at the end of the tail peduncle. A bioinspired propulsion system was developed for a robotic fish model. It is based on the combination of an elastic cord with a tail fin that is firmly attached to the cord. Two symmetric movable thrusts that simulate muscle contractions connect the tail fin to a servomotor. The propulsion system provides oscillatory tail movement that can be controlled for amplitude and frequency. This movement translates to the movement of the robotic fish, which executes the thunniform principle of locomotion. The body and tail fin of the robotic fish were designed using a computational model that simulates a virtual body in water. Subsequently, we constructed a prototype of the robotic fish and tested it under experimental conditions. Experiments were conducted to investigate the relationship between the robot’s kinematics and the dynamic parameters of the propulsion system. The results showed that increasing the frequency of tail fin oscillations led to an increase in the robot’s speed. At fixed frequencies, there was an interval of energetically efficient travel speeds up to a threshold velocity. Movement at higher speeds was achievable; however, it was accompanied by greater power consumption. The conclusion aligns with the data from COT studies on living tunas, indicating qualitative agreement. However, the robot’s values were quantitatively higher. Our robotic fish reached a maximum speed of approximately 0.4 BL/s, exceeding speeds in other works where a simplified tail section was used (0.22 BL/s [4], 0.254 BL/s [5]). Our study demonstrated a correlation between the efficiency of robot swimming and amplitude, which was previously unexplored in addition to previous findings on the relationship between tail beat frequency and swimming speed, as well as the dependence of frequency and swimming speed. The results showed that increasing the oscillation amplitude of the propulsion system, at a fixed frequency, only led to a rise in swimming speed up to a certain threshold. However, further increases in amplitude resulted in minimal speed increases at higher energy costs. An evaluation of energy efficiency was conducted, assessing its dependence on dynamic parameters of tail oscillation. The results show that the transport cost rises as the tail amplitude rises beyond the threshold. Furthermore, it was found that for a fixed frequency, an interval of energetic preferred speeds up to a threshold exists. Although moving at a higher speed is possible, it consumes more power. In general, it is preferable to increase caudal fin oscillation frequency rather than amplitude to increase swimming speed. These findings are in qualitative accordance with the outcomes of the numerical simulation of thunniform swimming.

Imaging Sonar Reveals Diel Movement of Fish Throughout a Developed Australian Estuary

Imaging Sonar Reveals Diel Movement of Fish Throughout a Developed Australian Estuary

Movement of an imperiled esocid fish in an agricultural drain

Animal movement is increasingly affected by human alterations to habitat and climate change. In wetland systems, widespread hydrologic alterations from agriculture have changed the shape, function, and stability of shallow streams and wetland habitats. These changes in habitat quality and quantity may be especially consequential for freshwater fishes such as Grass Pickerel (Esox americanus vermiculatus), a small predatory fish found in disjunct populations across southern Ontario and listed as Special Concern under Canada’s Species at Risk Act. To characterize Grass Pickerel movement response to stream-channel alterations, Fisheries and Oceans Canada implemented a tracking study to monitor the movements of a Grass Pickerel population in an agricultural drain on the Niagara Peninsula (Ontario, Canada). From 2009 to 2013, 2007 Grass Pickerel were tagged and tracked in the 37.3 km2 Beaver Creek watershed using a combination of mark-recapture surveys and eight fully automated passive integrated transponder tag antennas. Most individuals moved within 500 m (i.e., stationary fish) while 16% of the fish moved > 500 m (i.e., mobile fish), with a maximum median movement distance of 1.89 km and a maximum movement distance of 13.5 km (a long-tail distribution). Most movements occurred near the largest confluence where only a few were long-distance upstream or downstream movements. Mobile fish were larger than their stationary counterparts. Grass Pickerel in sites with higher abundance had more mobile fish, implying potential density dependence. Our results highlight that, while a long-distance dispersal ability exists in extant Grass Pickerel populations, the current conditions of riverscapes may prevent these dispersals from occurring. For declining Grass Pickerel populations, limitations to their movement ecology may substantially increase the likelihood of local extirpations.

Escaping the dry: Native and non‐native fish outmigration from a receding floodplain following managed inundation

Abstract Many fish rely on being able to move between rivers and floodplains to fulfil key life history events, but river regulation has reduced floodplain inundation compromising these connections and causing the loss of ecosystem function more generally. Managed inundations are being trialled in some systems as a solution, whereby engineered floods using built infrastructure, such as floodplain regulators, are used to deliver water to inundate floodplains. However, the use of managed inundations is still in early stages and their outcomes for native fish have been rarely assessed. We present the results from a series of investigations assessing the effectiveness of two managed inundations on the native fish community in a large floodplain in south‐eastern Australia. We firstly described changes in fish assemblages in wetlands before and after managed inundation (Aim 1). We then examined which potential exits are used by golden perch, a highly mobile species that regularly moves between rivers and floodplains (Aim 2), and then assessed outmigration patterns of native and non‐native species during receding phase from one of the major golden perch exits via a fishlock (Aim 3). Finally, we conducted two experiments to test if it was possible to modify operation of the fishlock to maximise fish movement by varying the length of the operating cycle, or whether operation occurs during the day or night (Aim 4). We found that native fish dominated the catch in wetlands before drawdown of the managed inundation, but that non‐native species, especially young‐of‐year carp, dominated after the drawdown (Aim 1). Outmigrating golden perch left the floodplain wetlands in a variety of locations but predominantly through a fishlock, which is a type of fishway (Aim 2). At this fishlock, native fish outmigrated before and during the early phase of the floodplain recession, moving to permanent riverine habitats, whereas non‐native fish (mostly carp) tended to migrate later in the recession especially as water levels dropped (Aim 3). There were no substantive differences in the numbers and size of fish moving through the fishlock at different operating cycle times (Aim 4). While there were no differences in numbers of non‐native carp migrating during the day or night, native species (carp gudgeon and Australian smelt) were more common during the day. Our study has provided knowledge of the eco‐hydraulic mechanisms of fish movement, in relation to managed inundaitons. This knowledge can be applied to help water managers plan floodplain watering regimes in the Murray‐Darling Basin to benefit native fish, while potentially restricting movement of undesirable non‐native species such as carp. More broadly, our results improve current understanding of fish movement in relation to managed floodplain recession, which is critical given the increased use of such managed inundations, and the need for information to help design and evaluate them.

Artificial Neural Network (ANN)-Based Pattern Recognition Approach Illustrates a Biphasic Behavioral Effect of Ethanol in Zebrafish: A High-Throughput Method for Animal Locomotor Analysis.

Variations in stress responses between individuals are linked to factors ranging from stress coping styles to the sensitivity of neurotransmitter systems. Many anxiolytic compounds can increase stressor engagement through the modulation of neurotransmitter systems and are used to investigate stress response mechanisms. The effect of such modulation may vary in time depending on concentration or environment, but those effects are hard to dissect because of the slow transition. We investigated the temporal effect of ethanol and found that ethanol-treated individual zebrafish larvae showed altered behavior that is different between drug concentrations and decreases with time. We used an artificial neural network approach with a time-dependent method for analyzing long (90 min) experiments on zebrafish larvae and found that individuals from the 0.5% group begin to show locomotor activity corresponding to the control group starting from the 60th minute. The locomotor activity of individuals from the 2% group after the 80th minute is classified as the activity of individuals from the 1.5% group. Our method shows three clusters of different concentrations in comparison with two clusters, which were obtained with the usage of a statistical approach for analyzing just the speed of fish movements. In addition, we show that such changes are not explained by basic behavior statistics such as speed and are caused by shifts in locomotion patterns.

Simple additive weighting – a recommended seeds selections system for nile tilapia fish farmer

Nile tilapias are known to be an economically important farmed fish in Indonesia. Due to its adaptability, this tilapia fish can thrive in various aquatic conditions, making them an important commercial fish to produce locally or export internationally. Because of this potential, this study aims to provide recommendations using the decision support system to facilitate fish farmer decision-making with the Simple Additive Weighting model. This approach is expected to provide recommendations to fish farmers, or the general public interested in having their own Nile tilapia brood stock. The fish in this research was selected randomly following six criteria, namely fish weight, length, movement, fin or body deformation, fish colour and fish stomach condition. The result-based decision making model in this study provides an accuracy of 86.6%.

Modeling ocean distributions and abundances of natural- and hatchery-origin Chinook salmon stocks with integrated genetic and tagging data.

Considerable resources are spent to track fish movement in marine environments, often with the intent of estimating behavior, distribution, and abundance. Resulting data from these monitoring efforts, including tagging studies and genetic sampling, often can be siloed. For Pacific salmon in the Northeast Pacific Ocean, predominant data sources for fish monitoring are coded wire tags (CWTs) and genetic stock identification (GSI). Despite their complementary strengths and weaknesses in coverage and information content, the two data streams rarely have been integrated to inform Pacific salmon biology and management. Joint, or integrated, models can combine and contextualize multiple data sources in a single statistical framework to produce more robust estimates of fish populations. We introduce and fit a comprehensive joint model that integrates data from CWT recoveries and GSI sampling to inform the marine life history of Chinook salmon stocks at spatial and temporal scales relevant to ongoing fisheries management efforts. In a departure from similar models based primarily on CWT recoveries, modeled stocks in the new framework encompass both hatchery- and natural-origin fish. We specifically model the spatial distribution and marine abundance of four distinct stocks with spawning locations in California and southern Oregon, one of which is listed under the U.S. Endangered Species Act. Using the joint model, we generated the most comprehensive estimates of marine distribution to date for all modeled Chinook salmon stocks, including historically data poor and low abundance stocks. Estimated marine distributions from the joint model were broadly similar to estimates from a simpler, CWT-only model but did suggest some differences in distribution in select seasons. Model output also included novel stock-, year-, and season-specific estimates of marine abundance. We observed and partially addressed several challenges in model convergence with the use of supplemental data sources and model constraints; similar difficulties are not unexpected with integrated modeling. We identify several options for improved data collection that could address issues in convergence and increase confidence in model estimates of abundance. We expect these model advances and results provide management-relevant biological insights, with the potential to inform future mixed-stock fisheries management efforts, as well as a foundation for more expansive and comprehensive analyses to follow.