Management Of Fish Populations Research Articles

Digital twins for land-based aquaculture: A case study for rainbow trout ( Oncorhynchus mykiss).

The virtual, digital counterpart of a physical object, referred as digital twin, derives from the Internet of Things (IoT), and involves real-time acquisition and processing of large data sets. A fully implemented system ultimately enables real-time and remote management, as well as the reproduction of real and forecasted scenarios. Under the emerging framework of Precision Fish Farming, which brings control-engineering principles to fish production, we set up digital twin prototypes for land-based finfish farms. The digital twin is aimed at supporting producers in optimizing feeding practices, oxygen supply and fish population management with respect to 1) fish growth performances; 2) fish welfare, and 3) environmental loads. It relies on integrated mathematical models which are fed with data from in-situ sensors and from external sources, and simulate several dynamic processes, allowing the estimation of key parameters describing the ambient environment and the fishes. A conceptual application targeted at rearing cycles of rainbow trout ( Oncorhynchus mykiss) in an operational in-land aquafarm in Italy is presented. The digital twin takes into account the disparate levels of automation and control that are found within this farm, and considerations are made on preferential directions for future developments. In spite of its potential, and not only in the aquaculture sector, the development of digital twins is still at its early stage. Furthermore, Precision Fish Farming applications in land-based systems as well as targeted at rainbow trout are novel developments.

Freshwater growth can provide a survival advantage to Interior Columbia River spring Chinook salmon after ocean entry

ABSTRACT: A prerequisite to effectively managing fish populations is to understand what factors and processes, including predation and changing environments, affect the survival of individuals. In anadromous fishes, the transition from freshwater to marine habitats is considered a critical period regulating population abundance due to high and variable mortality rates. During this period, conditions experienced in freshwater may influence size- and growth-selective mortality in the ocean. To determine if size- or growth-selective mortality occurred in juvenile Interior Columbia River spring Chinook salmon Oncorhynchus tshawytscha as they migrated through the Lower Columbia River and Estuary (LCRE) and during early marine residence, we examined 2 cohorts in years with differing survival (2016 and 2017). We reconstructed the size and growth of individual Chinook salmon from otoliths and compared these attributes in fish caught at 4 sites in the LCRE to those caught in the ocean off Oregon and Washington. We observed evidence of growth-selective mortality in 2017 but not 2016. Specifically, in 2017, when overall survival was lower, individuals caught in the ocean grew significantly faster in freshwater than individuals caught in the estuary. Given that the fish had resided in the ocean for an average of 30 d, these results indicate growth-selective mortality in 2017 occurred soon after ocean entry. The finding that growth in freshwater may impact marine survival adds to the growing body of evidence that processes occurring both prior to and after ocean entry impact the marine survival of this species.

Climate Change Effects on Fish Passability across a Rock Weir in a Mediterranean River

Climate change represents a major challenge for the management of native fish communities in Mediterranean rivers, as reductions in discharge may lead to a decrease in passability through small barriers such as weirs, both in temporary and perennial rivers. Through hydraulic modelling, we investigated how discharges from a large hydropower plant in the Tagus River are expected to affect the passability of native freshwater fish species through a rock weir (Pego, Portugal), equipped with a nature-like fish ramp. We considered not only mean daily discharge values retrieved from nearby gauging stations (1991–2005) for our flow datasets, but also predicted discharge values based on climatic projections (RCP) until the end of the century (2071–2100) for the Tagus River. Results showed that a minimum flow of 3 m3 s−1 may be required to ensure the passability of all species through the ramp and that passability was significantly lower in the RCP scenarios than in the historical scenario. This study suggests that climate change may reduce the passability of native fish species in weirs, meaning that the construction of small barriers in rivers should consider the decreases in discharge predicted from global change scenarios for the suitable management of fish populations.

Testicular development and reproductive references of Glossogobius giuris in Mekong Delta, Vietnam

The present study contributes information to the testicular development and reproductive aspects of Glossogobius giuris (Hamilton 1822), one of the target fishes in the Mekong Delta. Trawl nets were used to monthly collect fish specimens from January to December 2020 in four sites along Bassac River, from Cai Rang, Can Tho (CRCT) to Long Phu, Soc Trang (LPST), Hoa Binh, Bac Lieu (HBBL) and Dam Doi, Ca Mau (DDCM). Data analysis of 632 Glossogobius giuris individuals showed that five-stage of sperm development was found in testis histological slides. At stage IV of the testis, different phases of the sperm were observed, indicating that it is a multi-spawner, releasing sperms many times during the breeding season. Further analyses of the testis about apparent frequency and gonadosomatic index showed that this goby can release sperms monthly with a peak in the main wet season. The length at first maturity was observed at 7.24, 7.18, 7.43, and 6.57 cm of TL in CRCT, LPST, HBBL, and DDCM, respectively. The findings contribute essential information to fish population management and sustainable exploitation.

Critical information for fisheries monitoring may be available in social media

Abstract Fisheries monitoring is essential to evaluate and manage fish populations. Effective monitoring is particularly challenging in low‐ and middle‐income countries where fisheries often occur at large spatial scales and include multiple techniques. Recreational spearfishing, for instance, can be detrimental to fish populations and is often underrepresented in management strategies due to the lack of data. Because recreational fishers frequently share pictures of their catches online, social media can harbour valuable information. As a case study, freely available pictures in social media were used to assess the impacts of spearfishing on the endemic and endangered Brazilian parrotfish, Scarus trispinosus, that has experienced a sharp population decline in recent decades due to overfishing. It was found that S. trispinosus is widely captured by recreational spearfishing and at larger sizes when compared to artisanal fisheries, revealing complementary fishing pressures operating on different life stages of this species and a lack of compliance to current regulations. The number of users sharing these contents increased between 2007 and 2018, but declined thereafter until 2020. Identifying where spearfishing is more intense and the most targeted life‐stages can inform prioritization of management strategies. Social media can be a rapid and low‐cost tool to obtain nationwide fisheries information, especially for recreational fishing activities that have a flawed monitoring. The public disclosure of ‘trophy fishes’ can reveal lack of compliance to existing regulations and help fill critical information gaps on complementary fishing pressures. This approach may be applicable for many species and types of trophy fishing, providing valuable and useful information for management and conservation.

Size-selective competition between cod and pelagic fisheries for prey

Abstract Predators often predate on a limited size range of prey, which may or may not overlap with size ranges of same prey targeted by fisheries. When they do overlap, the effect of competition over that prey is immediate, as the predator removes prey, which are at the same time suitable for the fishery. However, if the predator consumes the same prey species as the fishery, but targets smaller prey sizes, this predation on smaller sizes may result in a potential loss of future, rather than current, fishing opportunities. Comparative analyses of predator size preference and fisheries selectivity are scarce, despite their relevance in the context of integrated management of fish populations. We evaluated how size-selective cod predation influences the dynamics of sprat and herring in the Baltic Sea, as well as the competition with pelagic fisheries through immediate and delayed effects. We found a large overlap (30–60%) between prey lengths targeted by cod and fisheries, which was largest in the 1970s–1980s, when cod had higher abundance and was larger in size. Cod generally consumes herring and sprat, which are smaller than those caught by the fisheries, causing both immediate and delayed effects on prey biomass available for the fisheries.

A comparative analysis of habitat quality between artificial and natural creeks in the Mediterranean killifish Aphanius fasciatus: Implications for conservation

Abstract In transitional water ecosystems, habitat loss is one of the major threats to fish biodiversity. This is particularly true in the case of temperate salt marshes. Good quality artificial novel habitats may compensate for the loss of natural habitats, acting as a refuge for fish populations. The aim of this study was to use coloured ornamental traits exhibited by the males of a small lagoon‐resident fish, the Mediterranean killifish Aphanius fasciatus (Valenciennes, 1821), to assess habitat quality in both the natural and artificial creeks of the Venice lagoon. The conspicuousness of two secondary sexual traits, the yellow/orange caudal fin pigmentation and the contrast between white and dark vertical bars on body sides, proved to be greater in artificial habitats compared to natural salt marshes, highlighting the refuge function of artificial creeks. The use of secondary sexual traits could be extended to other fish species and to other aquatic habitats as a non‐invasive approach. This would allow the identification of good quality habitats in the context of fish population management and conservation.

Age, Growth, and Sexual Maturity of the Crocodile Shark, Pseudocarcharias kamoharai, From the Eastern Atlantic Ocean

To better manage fish populations, scientists and fisheries managers use age and growth studies to conduct stock assessments or provide management advice. However, many non-targeted species, important to the marine ecosystem, such as Pseudocarcharias kamoharai still lack such studies which impede comprehensive management of the fisheries. This study presents the age, growth, and sexual maturity of this species from the Tropical Eastern Atlantic Ocean (TEA) by examining vertebral samples. All samples were collected by Chinese Tuna Fishery Scientific Observers between November 2012 and May 2020, with sizes ranging from 46 to 101 cm fork length (FL). Four age determination approaches applied on whole and sectioned vertebral centra were compared. Four growth models fitted to the age data were also compared and the AIC was used to select the most plausible model. Whole vertebral centra stained with alizarin red S solution showed clearer growth band-pairs, and age ranged from 2 to 10 years (females) and from 2 to 11 years (males). The three-parameter von Bertalanffy growth function presented the best fit to describe the growth of this species. The obtained parameters for males were L∞ = 110.4 cm FL, K = 0.26 year-1 and L∞ = 108.3 cm FL, K = 0.29 year-1 for females. Females reached their size at 50% maturity (FL50%) larger than males (80.5 and 74.5 cm FL, respectively). The estimated longevities were 11.95 and 13.33 years for females and males, respectively. More work is needed regarding P. kamoharai in different Oceans, though, this study adds significant life-history information that can contribute to the management and conservation of the species.

The commercially important shoemaker spinefoot, Siganus sutor, connects coral reefs to neighbouring seagrass meadows.

Spatial management of fish populations can potentially be optimized by determining the area of influence of a particular species. We performed an acoustic tagging study implemented on Denis Island in the Seychelles to assess the area of influence of the heavily targeted shoemaker spinefoot, Siganus sutor. We investigated whether this species acts as a mobile link between coral patches and seagrass meadows, and whether their movements differed between day and night. The study incorporated an array of 22 acoustic stations deployed within dense coral patches, seagrass meadows and mixed habitats of both seagrass and coral. Fifteen S. sutor carrying internal acoustic tags were monitored from November 2016 until May 2017. Detection patterns revealed them to be diurnal herbivores, with only rare nocturnal movements. Home-range estimates showed that individuals differed in their spatial range extents and habitats used, covering ~15% of the total shallow subtidal coastline of the island. However, they displayed very small daily movements (<200 m), concentrated mainly around sites within mixed coral and seagrass habitats. An optimal number of detections was recorded when the coral to seagrass area ratio was approximately 1.6:1. This ratio was confirmed through statistical prediction modelling. Identification of such links of commercially important species between networked habitats may help authorities consider incorporating seagrass meadows of the Seychelles into management discussions, which are currently lacking.

Fish diversity and relative abundance at mesohabitat level in Gumara River, Lake Tana Sub-basin, Ethiopia.

Information regarding fish diversity and relative abundance at mesohabitat level plays important roles in monitoring, protecting or managing fish populations and their habitats. Although the presence of different fish species has been reported in Gumara River by various studies, organized information on abundance and diversity of fish species at mesohabitat levels were not available. Such information is very important for the management of the declining fish fauna of Lake Tana. So, this study aimed at investigating the abundance and diversity of fish species at the mesohabitat level. Diversity and relative abundance of fishes have been studied in the Gumara River and its tributaries from November 2018 to April 2019. Physico-chemical parameters of water were measured using the in-situ multi-probe system. Fish sampling was conducted using a technique called point abundance sampling by electrofishing. Fish species identification was done by using reference books and specimens deposited in the laboratory at Bahir Dar fisheries and other aquatic life research center. A total of 3,880 fish specimens were collected from all sampling sites. Among the collected specimens, the most (53.14%) and least (0.26%) dominant were Enteromius humilis and Labeobarbus intermedius, respectively. Both of them are cyprinids. In addition to cyprinids, specimens from family Cichlidae (O. niloticus) and Clariidae (C. gariepinus) were examined and contributed only 0.67 and 0.34%, respectively. There was a significant variation in the abundance of species between habitats and sampling months. Shannon’s index (H'=1.21) and evenness value (J'=0.53) in the Gumara River indicate moderate pollution and uniform distribution of individuals. Among the six sampling sites, the highest (H'=1.30) and lowest (H'=0.94) diversity indices were recorded at sites in the upstream near Wanzaye hot spring and below the bridge, respectively. In terms of mesohabitat, the species diversity and evenness were higher in riffle (H'=1.25, J'=0.57) than run (H'=1.15, J'=0.55) and the pool (H'=1.11, J'=0.50). The result revealed that the abundance and diversity of fish in Gumara River varied between sites and mesohabitats and this might be due to attitudinal difference, physico-chemical parameters and impact of different human activities around the river. Therefore, emphasis should be given to the factors which may lead to the collapse of the fish habitats, especially water abstraction for irrigation. Detailed studies on the diversity, abundance, reproductive biology by collecting yearround data should be done to use them as management tools.

Analyzing habitat preferences of Capoeta razii (Teleostei: Cyprinidae) at different ages in the Zarem stream, Iran

Understanding habitat preference is important in many terms such as management of fish populations, assessment of river health, river restoration, etc. In this regard, we chose Capoeta razii , one of the most abundant species in the Caspian Sea rivers, to study its habitat preferences in different ages. As pilot, Zarem Stream, a main tributary of Tajan River with low pressures and high habitat diversity, was selected. After collecting fish species in different random points, the environmental variables in the sampled areas were measured immediately after sampling. Habitat preferences analysis for different ages of this species showed that each age has almost own specific preference in terms of flow velocity, depth as well as abiotic and biotic substrate.

Modeling Brook Trout Carrying Capacity in Owhi Lake, Washington, Using Bioenergetics

AbstractThe management of fish populations often requires an understanding of how density‐dependent effects influence population dynamics. In systems where natural populations are supplemented with stocking, the question of “how much food is available” becomes increasingly important. One typical approach for assessing density‐dependent interactions is to identify disparities between fish consumption rates and food availability. The objective of our study was to determine whether seasonal lake prey production could support Brook Trout Salvelinus fontinalis consumption demand in Owhi Lake, Washington, at observed abundances. Brook Trout were collected seasonally from 2015 to 2017 to obtain information on length, weight, age, diet, growth, and mortality. Population abundance was estimated in summer by using hydroacoustic surveys. Littoral invertebrates and pelagic zooplankton were collected concurrently with fish to enumerate biomass and production. Bioenergetics modeling was used to estimate prey consumption by Brook Trout. In conjunction with supply–demand comparisons, we used growth efficiencies and maximum consumption rates to further identify potential seasonal and annual food limitations. Our results suggest that prey production could support Brook Trout consumption demand for all years, but littoral invertebrate consumption was close to or exceeded prey production in summer and fall 2017. Growth efficiency was lowest and maximum consumption rates were highest in summer 2017 relative to all other seasons and years. In addition to observed diet switching from littoral invertebrates to zooplankton in summer 2016 and 2017, we concluded that lower growth efficiencies, lower annual survival rates, and increased consumption rates were influenced by littoral invertebrate production. The Owhi Lake Brook Trout stocking program may require adaptive management (i.e., annual evaluations) to balance natural recruitment.

Non‐indigenous fish in protected spaces: Trends in species distribution mediated by illegal stocking

Abstract Many freshwater non‐indigenous species (NISs) are stocked for recreational fishing, in some cases illegally in protected areas. In this study, fish communities were monitored using environmental DNA, electrofishing and anglers’ catches as the sources of samples in a mountainous Biosphere Reserve in Asturias (northern Spain), where stocking is forbidden. Three NISs have been introduced illegally in the protected area and have shown increasing populations in the last two decades. Two species used as fishing bait, Squalius carolitertii (chub) and Phoxinus phoxinus (minnow), are expanding in running waters. Oncorhynchus mykiss (rainbow trout) was also detected and is likely to have been introduced for angling or from fish farm escapes. The results suggest that sustained illegal stocking contributed to the increase of the three NISs. In contrast, Salmo trutta (brown trout) of northern European lineages, identified from *90 alleles at the LDH‐C1 locus, and formerly legally stocked for angling, is decreasing, most likely as a result of climate change. Climate change could also contribute to the expansion of the two non‐indigenous cyprinids to colder upstream areas. Through the application of a social survey, it was found that unlike other population groups, anglers in the region significantly preferred stocking over environmental improvement for the management of fish populations. The results obtained suggest that raising the awareness of anglers about the importance of safeguarding native fish species could help to prevent the spread of NISs in protected areas.

Acoustic deterrents to manage fish populations

Finding effective ways to direct native fish away from anthropogenic hazards and limit the spread of invasive species, without physical intervention, harming non-target fishes or interrupting aquatic commerce is a major challenge for fisheries management. One option is to target fish sensory systems to manipulate behavior using attractive or repulsive cues. Many, if not all species of fish, use sound as part of their behavioral repertoire and display varying degrees of phonotaxis. Sound has inherent advantages over other sensory stimuli such as light or odor as underwater sound attenuates slowly, is highly directional and is unimpeded by low light or water turbidity. This review details the use of acoustics to deter and guide fish movements for a wide variety of fishes, before critically assessing the benefits and limitations of the technology. No single method of fish deterrence is a “one size fits all”, and therefore this review will assist both managers and researchers attempting to use acoustic deterrents for different fish orders.

Otolith microstructure analysis based on wild young fish and its application in confirming the first annual increment in Tibetan Gymnocypris selincuoensis

Otolith microstructural features of larval and juvenile fish, and especially the confirmation of the first annulus, are important for studying the early life history of fish. In this study, otolith microstructure analysis was performed on 318 young Gymnocypris selincuoensis (99 larvae and 219 juveniles) collected from Lake Siling Co from May 2010 to June 2011. The time of the first annulus formation of otoliths in juveniles was confirmed. The results showed that lapilli were the most suitable otoliths for age determination of G. selincuoensis among the three pairs of otoliths. By comparing the microstructure features of the otolith edge of the wild juveniles before and after overwintering, the first annulus formation time of the lapilli of the 2010 generation of juveniles was confirmed to be from April 17 to May 3, 2011 using the daily increment analysis. On the lapillus, an opaque band was formed from mid-April through early November (the growing season of G. selincuoensis), and a translucent band (i.e., the annulus) was formed from early November to mid-April of the following year (the slow growth stage). The first daily increment outside of the first annulus was formed at an average water temperature of 1.69 °C, which is the lowest reported water temperature at which fish were able to form daily increments. Our proposed method to determine the time of the first annulus formation through otolith daily increment analysis provides a referential way for confirming annulus formation in fish. The high temporal resolution (at day level) of this method in estimating annulus formation time highlights its application potentials in studies of growing season length estimation and fish response to water temperature change, which can assist with fish population management and conservation challenges arising from climate and environmental changes.

Fish Communities, Habitat Use, and Human Pressures in the Upper Volta Basin, Burkina Faso, West Africa

Human pressures and loss of natural fish habitats led to a decline in fish populations in terms of abundances, biodiversity, and average size in sub-Sahelian Burkina Faso. Little knowledge exists about fish assemblages regarding their composition, their habitat preferences, or their sensitivity to or tolerance of human pressures. This research provides the first data-driven basis for sustainably managing fish and associated aquatic and terrestrial habitats. Surveys in four different regions sampled 18,000 specimens from 69 species during the dry season. Fish communities, available abiotic habitat conditions, habitat use, and human pressures were assessed and analyzed. Fish communities cluster into four distinct types, each dominated by either Cichlidae, Clariidae, Cyprinidae, or Alestidae and accompanied by specific other families and genera of fish. Habitat preferences of four key species (Labeo coubie, Bagrus bajad, Chelaethiops bibie, and Lates niloticus) were linked to ecological habitat conditions. Results show that physical parameters influence fish community composition and abundances and, when indexed according to pressure type, are linked to responses in fish metrics. Relative abundance either dropped (Mormyridae) or increased (Cichlidae, Cyprinidae) with rising pressure intensity, and some sentinel taxa (Auchenoglanis, Hydrocynus) were only found in low-pressure sites. The outcomes of this study provide basic knowledge of habitat availability, habitat use by fish, species associations, and human pressures and therefore provide the basis for effective conservation and management of fish populations.

Using Side‐Scan Sonar and N‐Mixture Modeling to Estimate Atlantic Sturgeon Spawning Migration Abundance

AbstractUnderstanding the relationship between number of spawners and recruitment is essential for managing fish populations. Atlantic Sturgeon Acipenser oxyrinchus (ATS) are endangered anadromous fish inhabiting the rivers, estuaries, and marine environments along the Atlantic coast of North America. Atlantic Sturgeon are periodic life history strategists that exhibit both spring and fall spawning migrations. Traditional capture–mark–recapture techniques can be used to estimate spawning run abundance but are resource intensive and potentially stressful on migrating individuals. Noninvasive methods, such as side‐scan sonar, can be a less stressful alternative to estimating abundance. We sampled the uppermost portion of the Savannah River, USA, over 50 occasions from August to November 2017 using side‐scan sonar. Bayesian N‐mixture modeling was used to estimate spawner abundance and covariate effects based on spatially and temporally replicated count data obtained from sonar recordings. We detected at least one ATS on each sampling occasion and estimated a maximum daily spawner abundance between 35 and 55 individuals (95% credible interval) within the sampled area during the 2017 fall spawning season. Maximum discharge significantly affected ATS detection, and site average maximum depth significantly affected ATS abundance. Our results suggest that side‐scan sonar can be used as an alternative to traditional mark–recapture techniques for spawner abundance estimation. Routine sampling by using our methods will efficiently produce spawning run estimates and provide insight regarding the effects of environmental covariates on spawner abundance seasonally.

Age truncation of alewife in Lake Michigan

Empirical evidence has shown increased variability in harvest and recruitment of exploited fish populations, which can result directly from exploitation or indirectly from interactions between external drivers and the internal dynamics of age-structured populations. We investigated whether predation in a freshwater system could affect a prey fish population, in the same way fishing affects targeted populations. Using fishery-independent trawl survey data and a suite of quantitative indicators, we evaluated changes in the alewife population in Lake Michigan. Our results provide evidence for a reduction in the mean spawner age, a reduction in the diversity of age classes and the distribution of biomass across them, and increased variability in the proportion of first time spawners in the spawning stock. We used wavelet analysis and estimates of lifetime egg production to demonstrate how the alewife population displays behaviors of instability as the overall biomass declines. Our results provide evidence that predation pressure can influence prey fish populations in a similar manner to fishing on harvested populations, and that conservation of a broad reproducing age structure is likely to be important for buffering against adverse environmental fluctuations and for sustainable management of fish populations.

Including 38 kHz in the standardization protocol for hydroacoustic fish surveys in temperate lakes

AbstractHydroacoustics has become a requisite method to assess fish populations and allows to describe the relationships of fish with other elements of the aquatic ecosystem. This nonintrusive method is currently an integral part of the sampling procedures recommended for fish stock assessment by the Water Framework Directive and has been standardized by the European Committee for Standardization [CEN (2014) CSN EN 15910 ‐ Water quality ‐ Guidance on the estimation of fish abundance with mobile hydroacoustic methods, Category: 7577 Water quality. Biological.]. In Europe, hydroacoustic surveys are performed in freshwater using different frequencies. Consequently, there is a need to evaluate if survey results can be compared. This study aimed to carry out in situ comparisons at the 38 kHz frequency (noted f) with two other commonly used frequencies, 70 and 200 kHz. The 38 kHz frequency has seldom been compared with other frequencies in freshwater although it is widely used worldwide, especially in the Great Lakes of North America and in Sweden. In 2016, hydroacoustic data were acquired in Lakes Annecy and Bourget using methods validated in previous studies that compared the frequencies 70, 120 and 200 kHz. This study showed similar density and biomass estimations as a function of frequency, density(f) and biomass(f), between the frequencies studied for low to moderate fish densities. For higher fish densities, the results were more variable and need to be verified. Fish density(f) and biomass(f) estimations sometimes exhibit differences between frequencies, which is not fully in agreement with theoretical calculations. The aim of this study was to evaluate frequency comparisons in practise. However, if the differences on acoustic metrics, density(f) or biomass(f) between frequencies were occasionally statistically significant, the differences were small enough to be considered negligible for fish population management. These analyses led to better knowledge of the responses from fish in temperate lakes for the studied frequencies. Our findings should be considered when revising the CEN standard.

Hypoxia during incubation does not affect aerobic performance or haematology of Atlantic salmon (Salmo salar) when re-exposed in later life.

Hypoxia in aquatic ecosystems is becoming increasingly prevalent, potentially reducing fish performance and survival by limiting the oxygen available for aerobic activities. Hypoxia is a challenge for conserving and managing fish populations and demands a better understanding of the short- and long-term impacts of hypoxic environments on fish performance. Fish acclimate to hypoxia via a variety of short- and long-term physiological modifications in an attempt to maintain aerobic performance. In particular, hypoxia exposure during early development may result in enduring cardio-respiratory modifications that affect future hypoxia acclimation capacity, yet this possibility remains poorly investigated. We incubated Atlantic salmon (Salmo salar) in normoxia (~100% dissolved oxygen [DO, as percent air saturation]), moderate hypoxia (~63% DO) or cyclical hypoxia (100–25% DO daily) from fertilization until 113 days post-fertilization prior to rearing all groups in normoxia for a further 8 months. At ~11 months of age, subsets of each group were acclimated to hypoxia (50% DO) for up to 44 days prior to haematology, aerobic metabolic rate and hypoxia tolerance measurements. Hypoxia exposure during incubation (fertilization to 113 days post-fertilization) did not affect the haematology, aerobic performance or hypoxia tolerance of juvenile salmon in later life. Juveniles acclimated to hypoxia increased maximum aerobic metabolic rate and aerobic scope by ~23 and ~52%, respectively, when measured at 50% DO but not at 100% DO. Hypoxia-incubated juveniles also increased haematocrit and haemoglobin concentration but did not affect acute hypoxia tolerance (critical oxygen level and DO at LOE). Thus, while Atlantic salmon possess a considerable capacity to physiologically acclimate to hypoxia by improving aerobic performance in low oxygen conditions, we found no evidence that this capacity is influenced by early-life hypoxia exposure.