Hatchery Environment Research Articles

Trade-offs in the adaptation towards hatchery and natural conditions drive survival, migration, and angling vulnerability in a territorial fish in the wild

Hatchery fish that support capture fisheries need to thrive in both hatchery and natural environments. We conducted joint experiments in both environments with individuals stemming from multiple generations held in captivity to test the performance of hatchery-reared ayu (Plecoglossus altivelis). Ayu is an annual, herbivorous, territorial, and amphidromous riverine fish native to Japan of high importance to recreational fisheries. Hatchery fish of the first hatchery generation exhibited poor growth and highest malformation rates relative to the second and following hatchery generations. The first generation offspring stocked into a natural stream also showed low survival and poor vulnerability to angling, suggesting that maladaptation to the hatchery environment explained the performance in the wild. By contrast, offspring of the seventh to ninth generations exhibited high growth in the hatchery environment, but when stocked into the wild they also exhibited low survival, maladapted migratory behaviour, and again poor vulnerability to angling. Consequently, intermediate generations held in captivity were found to offer the best fisheries performance and can thus be recommended for enhancements to support recreational fisheries.

Supportive breeders of Atlantic salmon Salmo salar have reduced fitness in nature

AbstractWild Atlantic salmon (Salmo salar) are in decline over the entire distribution area, and populations are enhanced by supportive breeding. Parental fish are sampled in rivers, crossed and the offspring reared in hatcheries until smolting when released, ready for ocean migration. Naturally reproducing salmon entering the River Imsa from the ocean were monitored from 1976 through 2013, and since 1982, supportive breeders spawning in the river were also monitored. The supportive breeders were first‐generation salmon, reared for 1—2 years in a hatchery before being released at the mouth of the river so they could migrate to sea (i.e., sea‐ranching). Wild and sea‐ranched salmon live in the ocean for 1—2 years before they return to the river for spawning. In years when only wild adults were present, mean number of smolts produced per 100 m2 river area and female breeder was 0.47. When there were 5% wild females, the mean production was only 0.088 (19%). The gradual decrease in offspring production with decreasing proportion of wild females (r2 = .41) indicates that the reduced offspring production was caused by inferior spawning behavior of hatchery females or reduced survival of their offspring in nature. Previous experimental evidence suggests that wild males fertilize the eggs of wild but also hatchery females. It is discussed how epigenetic effects caused by hatchery environments influence the developing juveniles, lead to phenotypic changes that may reduce their fitness in nature even after free ranging for a year or more in the ocean before they return and spawn.

Release of hatchery-reared brown trout (Salmo trutta) as a threat to wild populations? A case study from Austria

In spite of growing evidence pointing to ecological and genetic risks to wild fish populations, artificial propagation and stocking remain common practices for recreational fishery management. Moreover, even a cursory level of monitoring and evaluation of these risks is neglected, especially where fisheries are managed by private entities. Against this backdrop and with the goal of establishing a more integrated system of ecosystem-based management, this study aims to identify potential threats from the current practices and patterns of brown trout management in Austria. We surveyed 26 private brown trout hatchery operations in three Austrian provinces to examine and categorize the practices in the production of brown trout for stocking. Specifically, we examined the rearing practices and the “trading networks” among trout farmers for characteristics such as rearing history, operating principles, broodstock origins and maintenance, and output figures. Several risk-associated practices emerged, including introduction of brood from divergent lineages outside of Austrian watersheds, translocation and mixing of fish across major watersheds within Austria, and reinforced domestication across multiple generations of captivity. These practices jeopardize native populations by disrupting local adaptations resulting from mixing of native and non-native lineages, reducing genetic diversity within lineages from population bottlenecks, and lowering success of wild populations from domestication selection within the hatchery environment. The findings, which identify threats rather than directly measure impacts, are discussed within the context of concerns on the role of conserving intraspecific diversity for native brown trout fisheries. We conclude by suggesting the integration of ecological and genetic principles into propagation and stocking practices to achieve fishery management strategies more compatible with maintaining natural diversity and adaptive potential of brown trout in Austria.

Temporal Dynamics of DNA Methylation Patterns in Response to Rearing Juvenile Steelhead (Oncorhynchus mykiss) in a Hatchery versus Simulated Stream Environment.

Genetic selection is often implicated as the underlying cause of heritable phenotypic differences between hatchery and wild populations of steelhead trout (Oncorhynchus mykiss) that also differ in lifetime fitness. Developmental plasticity, which can also affect fitness, may be mediated by epigenetic mechanisms such as DNA methylation. Our previous study identified significant differences in DNA methylation between adult hatchery- and natural-origin steelhead from the same population that could not be distinguished by DNA sequence variation. In the current study, we tested whether hatchery-rearing conditions can influence patterns of DNA methylation in steelhead with known genetic backgrounds, and assessed the stability of these changes over time. Eyed-embryos from 22 families of Methow River steelhead were split across traditional hatchery tanks or a simulated stream-rearing environment for 8 months, followed by a second year in a common hatchery tank environment. Family assignments were made using a genetic parentage analysis to account for relatedness among individuals. DNA methylation patterns were examined in the liver, a relatively homogeneous organ that regulates metabolic processes and somatic growth, of juveniles at two time points: after eight months of rearing in either a tank or stream environment and after a subsequent year of rearing in a common tank environment. Further, we analyzed DNA methylation in the sperm of mature 2-year-old males from the earlier described treatments to assess the potential of environmentally-induced changes to be passed to offspring. Hepatic DNA methylation changes in response to hatchery versus stream-rearing in yearling fish were substantial, but few persisted after a second year in the tank environment. However, the early rearing environment appeared to affect how fish responded to developmental and environmental signals during the second year since novel DNA methylation differences were identified in the livers of hatchery versus stream-reared fish after a year of common tank rearing. Furthermore, we found profound differences in DNA methylation due to age, irrespective of rearing treatment. This could be due to smoltification associated changes in liver physiology after the second year of rearing. Although few rearing-treatment effects were observed in the sperm methylome, strong family effects were observed. These data suggest limited potential for intergenerational changes, but highlight the importance of understanding the effects of kinship among studied individuals in order to properly analyze and interpret DNA methylation data in natural populations. Our work is the first to study family effects and temporal dynamics of DNA methylation patterns in response to hatchery-rearing.

Embryonic development of Ganga river prawnMacrobrachium gangeticum(Bate)

Macrobrachium gangeticum (Bate) are commercially valuable prawns that are broadly distributed in the Ganga river that flows from northern to eastern India. We studied embryonic development from cleavage (blastomeres), segmentation, formation of optic vesicle, eye pigment development to larva formation, as these data are largely unknown in this species. We conducted this study using mature M. gangeticum broodstock placed in freshwater tanks. Just after spawning, females were kept in separate aerated tanks, where fecundity was estimated from the total number of eggs. Thereafter, egg samples from berried females were used to study their embryonic stages. The correlation coefficient between size and prawn weight, egg weight, egg number, body weight and egg mass of different sizes of prawns was analysed. Our results show that an increase in prawn size led to an increase in egg weight and egg number while decreases in body weight:egg mass ratio was noticed. Further results indicate that an increase in prawn weight had a positive impact on egg weight and egg number. The embryo development stages were used in this study as a tool to evaluate the development process of the prawn in a hatchery environment.

Contact with adult hen affects development of caecal microbiota in newly hatched chicks.

Chickens in commercial production are hatched in a clean hatchery environment in the absence of any contact with adult hens. However, Gallus gallus evolved to be hatched in a nest in contact with an adult hen which may act as a donor of gut microbiota. In this study, we therefore addressed the issue of microbiota development in newly hatched chickens with or without contact with an adult hen. We found that a mere 24-hour-long contact between a hen and newly hatched chickens was long enough for transfer of hen gut microbiota to chickens. Hens were efficient donors of Bacteroidetes and Actinobacteria. However, except for genus Faecalibacterium and bacterial species belonging to class Negativicutes, hens did not act as an important source of Gram-positive Firmicutes. Though common to the chicken intestinal tract, Lactobacilli and isolates from families Erysipelotrichaceae, Lachnospiraceae and Ruminococcaceae therefore originated from environmental sources instead of from the hens. These observation may have considerable consequences for the evidence-based design of the new generation of probiotics for poultry.

Implications of management on immunogenetic variation in the European grayling (Thymallus thymallus)

Implications of management on immunogenetic variation in the European grayling (Thymallus thymallus)

Is blood cortisol or vateritic otolith composition associated with natal dispersal or reproductive performance on the spawning grounds of straying and homing hatchery-produced chum salmon (Oncorhynchus keta) in Southeast Alaska?

ABSTRACTHoming with high fidelity to natal spawning grounds for reproduction is a hallmark of anadromous Pacific salmon biology, although low rates of dispersal (‘straying’) also occurs. Currently little is known about the proximate factors influencing straying, which limits our understanding of this fundamental biological phenomenon and impedes options for reducing straying-mediated interactions between wild and hatchery-produced individuals. We explored the potential role of stress experienced in captivity prior to intentional release to manifest in developmental irregularities and potentially influence rates of straying by adults. We compared two proxies for stress between groups of hatchery-produced individuals that had homed back to the hatchery or strayed to non-natal streams compared to wild individuals that were presumed to have homed to a wild spawning stream. Blood plasma cortisol was used to assess stress at the terminus of their migration, and percent frequency of vateritic otolith development within groups as a measure of stresses incurred during development. We found no evidence that either proxy for stress was associated with straying. No differences in cortisol concentrations were found between wild and hatchery-produced chum salmon that had homed or strayed, either in males (wild=95.9±175.7 ng/ml; stray=113.4±99.7 ng/ml; home=124.7±113.8 ng/ml) or females (wild=307.6±83.4 ng/ml; stray= 329.0±208.9 ng/ml; home=294.1±134.8 ng/ml); however, significant differences between males and females occurred in each group. The percent frequency of vaterite occurrence in otoliths of hatchery-produced chum salmon that either strayed (40% vaterite) or homed (45% vaterite) did not differ significantly, though rates of vaterite occurred less frequently in wild chum salmon (24%), which is consistent with other studies. Mass thermal marking of juvenile fish in hatcheries is unlikely to increase vateritic development as neither intensity (number of temperature changes) or complexity (number of temperature change sequences) of the mark was associated with frequency of vaterite occurrence. Though not associated with straying, cortisol concentrations were associated with shorter instream lifespan of both hatchery and wild individuals but did not appear to influence rates of egg retention in spawning females, suggesting an equivocal role in reproductive ecology. Our results are suggestive that stress induced during the early stages of rearing in a hatchery environment from marking or other causes may not increase straying later in life, though the higher rates of vaterite observed in hatchery-produced fish may come at a cost of increased marine mortality, due to the otoliths' role in navigation and hearing.

Effects of environmental enrichment on forebrain neural plasticity and survival success of stocked Atlantic salmon.

Fish reared for stocking programmes are severely stimulus deprived compared with their wild conspecifics raised under natural conditions. This leads to reduced behavioural plasticity and low post-release survival of stocked fish. Environmental enrichment can have positive effects on important life skills, such as predator avoidance and foraging behaviour, but the neural mechanisms underpinning these behavioural changes are still largely unknown. In this study, juvenile Atlantic salmon (Salmo salar) were reared in an enriched hatchery environment for 7weeks, after which neurobiological characteristics and post-release survival were compared with those of fish reared under normal hatchery conditions. Using in situ hybridization and qPCR, we quantified the expression of brain-derived neurotrophic factor (bdnf) and the neural activity marker cfos in telencephalic subregions associated with relational memory, emotional learning and stress reactivity. Aside from lower expression of bdnf in the Dlv (a region associated with relational memory) of enriched salmon, we observed no other significant effects of enrichment in the studied regions. Exposure to an enriched environment increased post-release survival during a 5month residence in a natural river by 51%. Thus, we demonstrate that environmental enrichment can improve stocking success of Atlantic salmon parr and that environmental enrichment is associated with changes in bdnf expression in the fish's hippocampus-equivalent structure.

Wood addition in the hatchery and river environments affects post‐release performance of overwintering brown trout

Abstract Habitat structural complexity affects the behaviour and physiology of individuals, and responses to the environment can be immediate or influence performance later in life through delayed effects. Here, we investigated how structural enrichment, both pre‐release in the hatchery rearing environment and post‐release in the wild, influenced winter growth and site fidelity of brown trout stocked into side channels of a regulated river. Experiencing structural enrichment in the rearing environment during 3 months in autumn had no pre‐release effect on growth, but a delayed positive effect after release during the subsequent winter. Moreover, trout recaptured in wood‐treated sections of the side channels had grown more than trout recaptured in control sections. Wood enrichment in the side channels also increased overwinter site fidelity. These results show that adding structure during a relatively short period may alter growth trajectories, and adding wood to side channels is a cost‐effective method to enhance winter habitat carrying capacity for juvenile salmonids in regulated rivers.

Neurobiology of Wild and Hatchery-Reared Atlantic Salmon: How Nurture Drives Neuroplasticity.

Life experiences in the rearing environment shape the neural and behavioral plasticity of animals. In fish stocking practices, the hatchery environment is relatively stimulus-deprived and does not optimally prepare fish for release into the wild. While the behavioral differences between wild and hatchery-reared fish have been examined to some extent, few studies have compared neurobiological characteristics between wild and hatchery-reared individuals. Here, we compare the expression of immediate early gene cfos and neuroplasticity marker brain-derived neurotrophic factor (bdnf) in telencephalic subregions associated with processing of stimuli in wild and hatchery-reared Atlantic salmon at basal and 30 min post (acute) stress conditions. Using in situ hybridization, we found that the expression level of these markers is highly specific per neuronal region and affected by both the origin of the fish, and exposure to acute stress. Expression of cfos was increased by stress in all brain regions and cfos was more highly expressed in the Dlv (functional equivalent to the mammalian hippocampus) of hatchery-reared compared to wild fish. Expression of bdnf was higher overall in hatchery fish, while acute stress upregulated bdnf in the Dm (functional equivalent to the mammalian amygdala) of wild, but not hatchery individuals. Our findings demonstrate that the hatchery environment affects neuroplasticity and neural activation in brain regions that are important for learning processes and stress reactivity, providing a neuronal foundation for the behavioral differences observed between wild and hatchery-reared fish.

Behavior of Antimicrobial Peptide K4 in a Marine Environment.

K4 is a de novo peptide with antibacterial activity on human pathogens. It has a short sequence (14 amino acids), with a cationic N-terminal moiety and an amphipathic ɑ-helix structure. The present paper demonstrates its activity on Vibrio bacteria in a marine environment. It was found non-toxic on marine organisms including Artemia salina, Dicentrarchus labrax, and Magallana gigas at different developmental stages, but influenced the growth of unicellular organisms like microalgae, depending on the algal strain and on K4 concentration. Furthermore, an original approach coupling liquid chromatography (RP-HPLC) and mass spectrometry (MS/MS) allowed us to monitor the degradation time course of the peptide for the first time in conditions close to a hatchery environment, i.e., in the presence of oyster spat. We detected truncated forms over time, and the full K4 was gradually no longer found in these filter-feeder oysters. Finally, using an automated optical density meter, we monitored the growth of several aquatic bacteria identified as pathogenic on animals. K4 had a bactericidal effect on Aeromonas salmonicida and Vibrio splendidus LGP32 at concentrations below 45μgmL-1. Our results show that K4 could be an environment-friendly alternative to antibiotics, non-toxic to several marine organisms. The use of K4 would be particularly useful to decrease the bacterial load associated with food intake in the early developmental stages of marine animals reared in hatcheries.

Structural and compositional mismatch between captive and wild Atlantic salmon (Salmo salar) parrs' gut microbiota highlights the relevance of integrating molecular ecology for management and conservation methods.

Stocking methods are used in the Province of Quebec to restore Salmo salar populations. However, Atlantic salmon stocked juveniles show higher mortality rates than wild ones when introduced into nature. Hatchery environment, which greatly differs from the natural environment, is identified as the main driver of the phenotypic mismatch between captive and wild parrs. The latter is also suspected to impact the gut microbiota composition, which can be associated with essential metabolic functions for their host. We hypothesized that hatchery‐raised parrs potentially recruit gut microbial communities that are different from those recruited in the wild. This study evaluated the impacts of artificial rearing on gut microbiota composition in 0+ parrs meant for stocking in two distinct Canadian rivers: Rimouski and Malbaie (Quebec, Canada). Striking differences between hatchery and wild‐born parrs’ gut microbiota suggest that microbiota could be another factor that could impact their survival in the targeted river, because the microbiome is narrowly related to host physiology. For instance, major commensals belonging to Enterobacteriaceae and Clostridiacea from wild parrs’ gut microbiota were substituted in captive parrs by lactic acid bacteria from the Lactobacillaceae family. Overall, captive parrs host a generalist bacterial community whereas wild parrs’ microbiota is much more specialized. This is the very first study demonstrating extensive impact of captive rearing on intestinal microbiota composition in Atlantic salmon intended for wild population stocking. Our results strongly suggest the need to implement microbial ecology concepts into conservation management of endangered salmon stocks supplemented with hatchery‐reared parrs.

Poultry hatcheries as potential reservoirs for antimicrobial-resistant Escherichia coli: A risk to public health and food safety

Hatcheries have the power to spread antimicrobial resistant (AMR) pathogens through the poultry value chain because of their central position in the poultry production chain. Currently, no information is available about the presence of AMR Escherichia coli strains and the antibiotic resistance genes (ARGs) they harbor within hatchezries. Therefore, this study aimed to investigate the possible involvement of hatcheries in harboring hemolytic AMR E. coli. Serotyping of the 65 isolated hemolytic E. coli revealed 15 serotypes with the ability to produce moderate biofilms, and shared susceptibility to cephradine and fosfomycin and resistance to spectinomycin. The most common β-lactam resistance gene was blaTEM, followed by blaOXA-1, blaMOX-like,blaCIT-like,blaSHV and blaFOX. Hierarchical clustering of E. coli isolates based on their phenotypic and genotypic profiles revealed separation of the majority of isolates from hatchlings and the hatchery environments, suggesting that hatchling and environmental isolates may have different origins. The high frequency of β-lactam resistance genes in AMR E. coli from chick hatchlings indicates that hatcheries may be a reservoir of AMR E. coli and can be a major contributor to the increased environmental burden of ARGs posing an eminent threat to poultry and human health.

Flavobacteria colonizing the early life stages of hatchery-incubated Chinook salmon Oncorhynchus tshawytscha (Walbaum 1792) are markedly diverse.

Flavobacterial diseases are significant impediments to hatchery-based fishery conservation and aquaculture productivity worldwide. Recent studies revealed a multitude of novel flavobacteria within the reproductive fluids and unfertilized eggs of feral Chinook salmon Oncorhynchus tshawytscha broodstock, some of which were associated with systemic disease. Herein, embryonated eggs/fry from these broodstock were assayed for flavobacteria while in incubator stacks in three hatcheries over 2years, as was the water entering hatchery incubators. Overall, >65% of sampled eggs and 38% of fry were colonized by flavobacteria. One hundred and ninety-one egg and fry-associated flavobacterial isolates were characterized phenotypically and via 16S rRNA gene sequencing and phylogenetic analyses, revealing that the majority fell into 22 clades (i.e., 15 Flavobacterium spp. groups and seven Chryseobacterium spp. groups) that varied in presence by facility. Although some matched previously described fish-pathogenic species, the majority were distinct from all described flavobacteria and likely represent novel species. Of concern, iodophor disinfection at the commonly utilized dose/duration for egg-surface disinfection did not eliminate flavobacteria. Results also implicated maternal routes of infection and source water for some flavobacteria. In total, study findings underscore the complexity of flavobacterial ecology within hatchery environments and highlight the need for improved hatchery biosecurity practices.

Predation, metabolic priming and early life-history rearing environment affect the swimming capabilities of growth hormone transgenic rainbow trout.

The period of first feeding, when young salmonid fishes emerge from natal stream beds, is one fraught with predation risk. Experiments conducted in semi-natural stream mesocosms have shown that growth hormone transgenic salmonids are at greater risk of predation than their non-transgenic siblings, due partly to the higher metabolic demands associated with transgenesis, which force risky foraging behaviours. This raises questions as to whether there are differences in the swim-performance of transgenic and non-transgenic fishes surviving predation experiments. We tested this hypothesis in wild-origin rainbow trout (Oncorhynchus mykiss) that were reared from first feeding in semi-natural stream mesocosms characterized by complex hydrodynamics, the presence of predators and oligotrophic conditions. Using an open-flume raceway, we swam fish and measured their capacity for burst-swimming against a sustained flow. We found a significant genotype effect on burst-performance, with transgenic fish sustaining performance longer than their wild-type siblings, both in predator and predator-free stream segments. Importantly, this effect occurred before differences in growth were discernable. We also found that mesocosm-reared fish had greater burst-performance than fish reared in the controlled hatchery environment, despite the latter being unexposed to predators and having abundant food. Our results suggest a potential interaction between predation and metabolic priming, which leads to greater burst capacity in transgenic trout.

Genetic differences between wild and hatchery-bred brown trout (Salmo trutta L.) in single nucleotide polymorphisms linked to selective traits.

To study effects from natural selection acting on brown trout in a natural stream habitat compared with a hatchery environment, 3,781 single nucleotide polymorphism (SNP) markers were analyzed in three closely related groups of brown trout (Salmo trutta L.). Autumn (W/0+, n = 48) and consecutive spring (W/1+, n = 47) samples of brown trout individuals belonging to the same cohort and stream were retrieved using electrofishing. A third group (H/1+, n = 48) comprised hatchery‐reared individuals, bred from a mixture of wild parents of the strain of the two former groups and from a neighboring stream. Pairwise analysis of FST outliers and analysis under a hierarchical model by means of ARLEQUIN software detected 421 (10.8%) candidates of selection, before multitest correction. BAYESCAN software detected 10 candidate loci, all of which were included among the ARLEQUIN candidate loci. Body length was significantly different across genotypes at 10 candidate loci in the W/0+, at 34 candidate loci in the W/1+ and at 21 candidate loci in the H/1+ group. The W/1+ sample was tested for genotype‐specific body length at all loci, and significant differences were found in 10.6% of all loci, and of these, 14.2% had higher frequency of the largest genotype in the W/1+ sample than in W/0+. The corresponding proportion among the candidate loci of W/1+ was 22.7% with genotype‐specific body length, and 88.2% of these had increased frequency of the largest genotype from W/0+ to W/1+, indicating a linkage between these loci and traits affecting growth and survival under this stream's environmental conditions. Bayesian structuring of all loci, and of the noncandidate loci suggested two (K = 2), alternatively four clusters (K = 4). This differed from the candidate SNPs, which suggested only two clusters. In both cases, the hatchery fish dominated one cluster, and body length of W/1+ fish was positively correlated with membership of one cluster both from the K = 2 and the K = 4 structure. Our analysis demonstrates profound genetic differentiation that can be linked to differential selection on a fitness‐related trait (individual growth) in brown trout living under natural vs. hatchery conditions. Candidate SNP loci linked to genes affecting individual growth were identified and provide important inputs into future mapping of the genetic basis of brown trout body size selection.

Early life traits of farm and wild Atlantic salmon Salmo salar and first generation hybrids in the south coast of Newfoundland.

This study examined fertilization rates, survival and early life-trait differences of pure farm, wild and first generation (F1) hybrid origin embryos after crossing farm and wild Atlantic salmon Salmo salar. Results show that despite a trend towards higher in vitro fertilization success for wild females, differences in fertilization success in river water are not significantly different among crosses. In a hatchery environment, wild females' progeny (pure wild and hybrids with wild maternal parent) hatched 7-11 days earlier than pure farm crosses and hybrids with farm maternal parents. In addition, pure wild progeny had higher total lengths (LT ) at hatch than pure farm crosses and hybrids. Directions in trait differences need to be tested in a river environment, but results clearly show the maternal influence on early stages beyond egg-size differences. Differences in LT were no longer significant at 70 days post hatch (shortly after the onset of exogenous feeding) showing the need to investigate later developmental stages to better assess somatic growth disparities due to genetic differences. Higher mortality rates of the most likely hybrids (farm female × wild male hybrids) at egg and fry stages and their delayed hatch suggest that these F1 hybrids might be less likely to survive the early larval stages than wild stocks.

The Impact of Different Hatchery Rearing Environments on Smolt‐to‐Adult Survival of Spring Chinook Salmon

AbstractThe aim of this study was to assess the effect of differing hatchery rearing environments on smolting, early male maturation, and smolt‐to‐adult return rates (SARs) in Chinook Salmon Oncorhynchus tshawytscha. In this investigation, SARs were compared for spring Chinook Salmon from Hood River stock reared at three different hatcheries and then released into the Hood River, replicated over three separate years (2010–2012). Differences in SARs were found both between rearing groups and release years. Smolts reared at Pelton Ladder had consistently higher SARs than those reared at either Parkdale or Carson hatcheries. Smolt length at release was positively correlated to SARs across years and rearing groups. In addition, multiple regression models suggested that attributes related to smolt quality were positively related to SARs while the minijack rate was negatively related to SAR. Migration of smolts downstream after release was also assessed. Larger smolts were faster downstream migrants and migration rate was positively related to subsequent SAR. Differences in smolt quality and SAR between rearing groups is attributed to differing patterns of growth in the different hatchery environments. The best‐performing smolts came from rearing groups that experienced a strong seasonal change in growth rate: relatively high growth in the summer, reduced growth and depletion of energetic stores in the autumn and winter, and then increased growth again in the spring. This pattern of seasonal anabolic and catabolic changes has been termed the wild fish template, and generating this physiological pattern generally may be applicable to hatchery‐reared Chinook Salmon.Received August 3, 2016; accepted December 20, 2016 Published online March 30, 2017

Training camp—A way to improve survival in European lobster juveniles?

A series of experiments was conducted to test if keeping hatchery-produced European lobster juveniles (Homarus gammarus) in an enriched environment with substrate and shelter would improve anti-predator behaviour and survival in a competition setting. Newly hatched postlarvae (stage IV) were divided into two treatments. Naïve postlarvae were raised in single compartments, while trained postlarvae were released communally into tanks with substrate and shelter, allowing for developing burrowing and shelter-seeking behaviour and interactions with conspecifics. The duration of the treatment lasted 181days in 2007/2008 and 226days in 2008/2009. In the second experiment, 4-mo old juveniles were purchased from a commercial hatchery and divided into the same two treatment groups. The treatments were considerably shorter, lasting 47days. At the end of the treatment period an equal number of juveniles from each treatment was released into experimental units with substrate and shelter i.e. semi-natural system for a period of 91–145days. Number of shelters was half the total number of juveniles to induce competition for shelters. In both experiments, trained juveniles occupied more shelters and had higher survival than naïve juveniles. Combining all experiments, average survival was 53% in trained lobsters compared with 18% in the naïve lobsters. These results are the first to demonstrate that enriching the hatchery environment for a period of time (a minimum of 47days here) while rearing European lobster juveniles increased their shelter occupancy and their survival compared to naïve juveniles the same size and age. Survival rates were 3–4 times higher in trained compared to naïve lobsters after 145days.