The effects of simulated catch-and-release angling on adult Atlantic salmon (Salmo salar) and their offspring

Fish, including Atlantic salmon (Salmo salar), are released by anglers after capture as part of a fisheries management tool known as catch and release (C&R) angling. This has been introduced as a conservation measure to try and halt, or even reverse, the continuous decline in Atlantic salmon numbers. Consequently, prespawned salmon may now experience C&R during the freshwater migration to the spawning grounds. Yet, there is still limited information in this area, including how stress from capture prior to breeding can affect not only the fecundity of the parents, but also the phenotype of the offspring. This study explores how two of the main stressors associated with C&R angling, exercise and air exposure, experienced by the parents shortly (5 – 18 days) prior to spawning affect adult mortality, physiology and reproduction. It also investigates the effects of simulated C&R on the early developmental stages of the progeny, as well as examines its influences on key behavioural (risk-taking behaviour, activity, exploration, aggression, and dominance) and physiological (SMR, MMR, AS) traits in offspring. An equal number of male and female wild adult Atlantic salmon were captured using a permanent fish trap, set up by the Cromarty Firth Fisheries, on the river Blackwater, N. Scotland, during their spawning migration. They then experienced one of three disturbance protocols that comprised of exercise (120 s) and air exposure (0, 60, or 120 s) of different duration, similarly to what they would encounter during a C&R angling event. There was also a fourth group present that did not experience any additional disturbance and was therefore used as baseline (control group). Each experimental fish (of either sex) was later mated (using IVF) with a non-experimental counterpart, and the offspring were reared under fixed conditions. Experimental parent mortality was unaffected by the simulated C&R, however the growth rate of the fungus Saprolegnia spp. on the body of the fish increased. Furthermore, males from the treatment group exercise + extended air produced sperm that survived for longer once activated (i.e. had an increased maximum duration of sperm motility). Females that experienced disturbance spawned at the usual time, but with smaller clutches. An increase in egg and fry mortality was noted for the groups whose parents were exposed to air, mostly due to higher mortality during egg shocking (a normal husbandry practice in hatcheries to separate non-viable eggs) and an increase in fry mortality during a 12-day fungal (Saprolegnia spp.) outbreak. Moreover, adults from the most extreme treatment group (exercise + extended air exposure) produced offspring that were smaller at first feeding. As for offspring behaviour, both the activity and exploration of a novel environment were lower in the treatments whose experimental parent was exercised and then air exposed for an extended period. Similar results in exploration were observed by the offspring in the exercise group. Yet, exploration in the most extreme disturbance group was improved as the fish became bigger. Progeny from the same treatments, ‘exercise’ and ‘exercise + extended air’ also displayed higher levels of aggression. Interestingly however, during the dominance trials, both these treatment groups were subordinate to offspring from the control treatment. Fish from the control treatment exhibited dominance over the fish from the disturbed parents during the trials on the first two days, but an absence of clear dominance was observed on the third day. There was no observable difference in dominance status between the treatment ‘exercise’ and ‘exercise + extended air’ treatments. The metabolism of the offspring was only affected in the exercise group, where both the MMR and AS were reduced. These results suggest that stressing the parents shortly before spawning will not affect the timing of the spawning, but it could influence the reproductive success of the parents. Furthermore, it indicates that disturbing the parents, especially air exposing them for more than 60 s, could adversely affect the early developmental stages of the offspring, including those behavioural traits which could influence dispersal and competition from feeding territories, and thus reduce their chances of survival. The results therefore have implications for both the period over which C&R is allowed and the way in which it is implemented by anglers

Does pre-spawning catch and release angling affect offspring telomere dynamics in Atlantic salmon?

The practice of ‘catch and release’ (C&R) angling confers a balance between animal welfare, conservation efforts and preserving the socio-economic interests of recreational angling. However, C&R angling can still cause exhaustion and physical injury, and often exposes the captured fish to the stress of air exposure. Therefore, the true conservation success of C&R angling depends on whether the angled individuals then survive to reproduction and whether there are any persisting effects on subsequent generations. Here we tested the hypothesis that the stress of C&R angling is then passed on to offspring. We experimentally manipulated the C&R experience of wild adult salmon prior to the spawning season. These parental fish either underwent a C&R simulation (which involved exercise with/without air exposure) or were left as control individuals. We then measured the telomere length of the arising offspring (at the larval stage of development) since previous studies have linked a shorter telomere length with reduced fitness/longevity and the rate of telomere loss is thought to be influenced by stress. Family-level telomere length was positively related to rate of growth. However, the telomere lengths of the salmon offspring were unrelated to the C&R experience of their parents. This may be due to there being no intergenerational effect of parental stress exposure on offspring telomeres, or to any potential effects being buffered by the significant telomere elongation mechanisms that are thought to occur during the embryonic and larval stages of development. While this may suggest that C&R angling has a minimal intergenerational effect on offspring fitness, there have been numerous other reports of negative C&R effects, therefore we should still be aiming to mitigate and refine such practices, in order to minimize their impacts on fish populations

Simulated pre-spawning catch and release of wild atlantic salmon (Salmo salar) results in faster fungal spread and opposing effects on female and male proxies of fecundity

Atlantic salmon are increasingly being released after capture by anglers. Yet, there are still unknown effects on the fish being subjected to the process of catch and release. Capture too close to spawning could have adverse effects on fish, and such data are important for setting appropriate closed seasons. This study examines how stressors related to catch and release experienced shortly before spawning affects adult mortality, vulnerability to Saprolegnia spp., and reproductive traits. Adult salmon were collected from the river Blackwater, Scotland, towards the end of their migration and were exposed to one of four protocols comprising exercise and air exposure of different durations. The experimental stressors increased the growth rate of the fungus Saprolegnia spp. over the body of the fish. Moreover, male salmon from the most disturbed group exhibited an increase in the maximum duration of their sperm motility. Lastly, females that experienced exercise and/or air exposure spawned at the usual time but with fewer eggs. These suggest that there may be benefits from preventing angling close to the time of spawning

Guidelines for reporting methods to estimate metabolic rates by aquatic intermittent-flow respirometry

Interest in the measurement of metabolic rates is growing rapidly, because of the importance of metabolism in advancing our understanding of organismal physiology, behaviour, evolution and responses to environmental change. The study of metabolism in aquatic animals is undergoing an especially pronounced expansion, with more researchers utilising intermittent-flow respirometry as a research tool than ever before. Aquatic respirometry measures the rate of oxygen uptake as a proxy for metabolic rate, and the intermittent-flow technique has numerous strengths for use with aquatic animals, allowing metabolic rate to be repeatedly estimated on individual animals over several hours or days and during exposure to various conditions or stimuli. There are, however, no published guidelines for the reporting of methodological details when using this method. Here, we provide the first guidelines for reporting intermittent-flow respirometry methods, in the form of a checklist of criteria that we consider to be the minimum required for the interpretation, evaluation and replication of experiments using intermittent-flow respirometry. Furthermore, using a survey of the existing literature, we show that there has been incomplete and inconsistent reporting of methods for intermittent-flow respirometry over the past few decades. Use of the provided checklist of required criteria by researchers when publishing their work should increase consistency of the reporting of methods for studies that use intermittent-flow respirometry. With the steep increase in studies using intermittent-flow respirometry, now is the ideal time to standardise reporting of methods, so that - in the future - data can be properly assessed by other scientists and conservationists

Unpublished Mediterranean and Black Sea records of marine alien, cryptogenic, and neonative species

To enrich spatio-temporal information on the distribution of alien, cryptogenic, and neonative species in the Mediterranean and the Black Sea, a collective effort by 173 marine scientists was made to provide unpublished records and make them open access to the scientific community. Through this effort, we collected and harmonized a dataset of 12,649 records. It includes 247 taxa, of which 217 are Animalia, 25 Plantae and 5 Chromista, from 23 countries surrounding the Mediterranean and the Black Sea. Chordata was the most abundant taxonomic group, followed by Arthropoda, Mollusca, and Annelida. In terms of species records, Siganus luridus, Siganus rivulatus, Saurida lessepsianus, Pterois miles, Upeneus moluccensis, Charybdis (Archias) longicollis, and Caulerpa cylindracea were the most numerous. The temporal distribution of the records ranges from 1973 to 2022, with 44% of the records in 2020–2021. Lethrinus borbonicus is reported for the first time in the Mediterranean Sea, while Pomatoschistus quagga, Caulerpa cylindracea, Grateloupia turuturu, and Misophria pallida are first records for the Black Sea; Kapraunia schneideri is recorded for the second time in the Mediterranean and for the first time in Israel; Prionospio depauperata and Pseudonereis anomala are reported for the first time from the Sea of Marmara. Many first country records are also included, namely: Amathia verticillata (Montenegro), Ampithoe valida (Italy), Antithamnion amphigeneum (Greece), Clavelina oblonga (Tunisia and Slovenia), Dendostrea cf. folium (Syria), Epinephelus fasciatus (Tunisia), Ganonema farinosum (Montenegro), Macrorhynchia philippina (Tunisia), Marenzelleria neglecta (Romania), Paratapes textilis (Tunisia), and Botrylloides diegensis (Tunisia).peer-reviewe

The effects of simulated catch-and-release angling on adult Atlantic salmon (Salmo salar) and their offspring

The dataset contains data used for both the thesis, and future publications

Endobiotic communities of Marine Sponges in Cyprus (Levantine Sea)

Sponges host cryptic endobionts within their network of canals, with representatives from all major animal phyla. This study investigates the endobiotic community of four sponge species (Spongia officinalis, Sarcotragus spinosulus, Ircinia cf. variabilis and Ircinia oros) that were collected during scientific trawl surveys in the coastal area of Cyprus. Moreover, it examines the endobiotic community composition of S. spinosulus in relation to sponges' volume, and various environmental variables. In general, the four sponge endobiotic communities were similar; S. officinalis had a significantly different community composition to I. cf. variabilis and I. oros. The phyla identified followed the general infauna composition of sponges, with the relative abundances of the dominant phyla, Arthropoda and Annelida, ranging from 66.9 - 83.7 % and 4.8–26.5 %, respectively. The highest intensity (I) corresponded to the isopod Cymodoce truncata in S. officinalis (I = 85 individuals/sponge) and S. spinosulus (I = 27.2 individuals/sponge). A general linear model also suggested that distance from shore influenced the total endobiotic abundance of S. spinosulus. This is the first sponge endobiotic community baseline study that covers the whole coastal area of the Republic of Cyprus and is particularly important due to potential changes of Eastern Mediterranean endobiotic communities due to the invasion through the Suez Canal of non-indigenous species

Climate change induced deprivation of dietary essential fatty acids can reduce growth and mitochondrial efficiency of wild juvenile salmon

1. Omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) are essential micronutrients for optimal functioning of cellular metabolism and for somatic growth of all vertebrates including fishes. In addition, n-3 LC-PUFA could also play a key role in response of fishes and other ectothermic vertebrates to changing temperatures. 2. An important, but largely overlooked, consequence of climate change is the reduced availability of dietary n-3 LC-PUFA in aquatic food webs. Changes in availability of dietary n-3 LC-PUFA have recently been proposed as a major driver of novel adaptations and diversification of consumers. Yet, there is only limited knowledge about how n-3 LC-PUFA depletion in aquatic food-webs will affect the performance of wild fishes. 3. Here we combine biochemistry and physiology at the cellular level with physiological and cognitive processes at the whole-animal level to test how ecologically relevant deprivation of n-3 LC-PUFA affects performance of wild juvenile Atlantic salmon (Salmo salar). 4. We found that juvenile salmon had a limited capacity to maintain the fatty acid profile of both muscle and brain under a n-3 LC-PUFA-deficient diet. Despite these findings, brain tissues showed remarkable functional stability in mitochondrial metabolism, and we found no effect of diet on learning ability. However, we found that mitochondrial efficiency in muscles and the somatic growth were reduced under a n-3 LC-PUFA-deficient diet. Importantly, we discovered that the somatic growth of juvenile salmon within both treatments decreased with increasing rate of DHA synthesis and retention. 5. Since DHA is essential for functioning of cellular metabolism, which together with body size are traits closely related to fitness of wild fishes, we suggest that the trade-off between growth rate and accumulation of DHA could play a critical role in resilience of juvenile salmon to the ongoing rapid environmental change

Climate change induced deprivation of dietary essential fatty acids can reduce growth and mitochondrial efficiency of wild juvenile salmon

1. Omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) are essential micronutrients for optimal functioning of cellular metabolism and for somatic growth of all vertebrates including fishes. In addition, n-3 LC-PUFA could also play a key role in response of fishes and other ectothermic vertebrates to changing temperatures. 2. An important, but largely overlooked, consequence of climate change is the reduced availability of dietary n-3 LC-PUFA in aquatic food webs. Changes in availability of dietary n-3 LC-PUFA have recently been proposed as a major driver of novel adaptations and diversification of consumers. Yet, there is only limited knowledge about how n-3 LC-PUFA depletion in aquatic food-webs will affect the performance of wild fishes. 3. Here we combine biochemistry and physiology at the cellular level with physiological and cognitive processes at the whole-animal level to test how ecologically relevant deprivation of n-3 LC-PUFA affects performance of wild juvenile Atlantic salmon (Salmo salar). 4. We found that juvenile salmon had a limited capacity to maintain the fatty acid profile of both muscle and brain under a n-3 LC-PUFA-deficient diet. Despite these findings, brain tissues showed remarkable functional stability in mitochondrial metabolism, and we found no effect of diet on learning ability. However, we found that mitochondrial efficiency in muscles and the somatic growth were reduced under a n-3 LC-PUFA-deficient diet. Importantly, we discovered that the somatic growth of juvenile salmon within both treatments decreased with increasing rate of DHA synthesis and retention. 5. Since DHA is essential for functioning of cellular metabolism, which together with body size are traits closely related to fitness of wild fishes, we suggest that the trade-off between growth rate and accumulation of DHA could play a critical role in resilience of juvenile salmon to the ongoing rapid environmental change

Guidelines for reporting methods to estimate metabolic rates by aquatic intermittent-flow respirometry

Interest in the measurement of metabolic rates is growing rapidly, because of the importance of metabolism in advancing our understanding of organismal physiology, behaviour, evolution and responses to environmental change. The study of metabolism in aquatic animals is undergoing an especially pronounced expansion, with more researchers utilising intermittent-flow respirometry as a research tool than ever before. Aquatic respirometry measures the rate of oxygen uptake as a proxy for metabolic rate, and the intermittent-flow technique has numerous strengths for use with aquatic animals, allowing metabolic rate to be repeatedly estimated on individual animals over several hours or days and during exposure to various conditions or stimuli. There are, however, no published guidelines for the reporting of methodological details when using this method. Here, we provide the first guidelines for reporting intermittent-flow respirometry methods, in the form of a checklist of criteria that we consider to be the minimum required for the interpretation, evaluation and replication of experiments using intermittent-flow respirometry. Furthermore, using a survey of the existing literature, we show that there has been incomplete and inconsistent reporting of methods for intermittent-flow respirometry over the past few decades. Use of the provided checklist of required criteria by researchers when publishing their work should increase consistency of the reporting of methods for studies that use intermittent-flow respirometry. With the steep increase in studies using intermittent-flow respirometry, now is the ideal time to standardise reporting of methods, so that – in the future – data can be properly assessed by other scientists and conservationists