The anadromous life cycle of Atlantic salmon Salmo salar involves long migrations to novel environments and challenging physiological transformations when moving between salt-free and salt-rich waters. In this article, (1) environmental factors affecting the migration behaviour and survival of smolts and post-smolts during the river, estuarine and early marine phases, (2) how behavioural patterns are linked to survival and (3) how anthropogenic factors affect migration and survival are synthesized and reviewed based on published literature. The timing of the smolt migration is important in determining marine survival. The timing varies among rivers, most likely as a consequence of local adaptations, to ensure sea entry during optimal periods. Smolts and post-smolts swim actively and fast during migration, but in areas with strong currents, their own movements may be overridden by current-induced transport. Progression rates during the early marine migration vary between 0.4 and 3.0 body lengths s(-1) relative to the ground. Reported mortality is 0.3-7.0% (median 2.3) km(-1) during downriver migration, 0.6-36% (median 6.0) km(-1) in estuaries and 0.3-3.4% (median 1.4) km(-1) in coastal areas. Estuaries and river mouths are the sites of the highest mortalities, with predation being a common cause. The mortality rates varied more among studies in estuaries than in rivers and marine areas, which probably reflects the huge variation among estuaries in their characteristics. Behaviour and survival during migration may also be affected by pollution, fish farming, sea lice Lepeophtheirus salmonis, hydropower development and other anthropogenic activities that may be directly lethal, delay migration or have indirect effects by inhibiting migration. Total mortality reported during early marine migration (up to 5-230 km from the river mouths) in the studies available to date varies between 8 and 71%. Hence, the early marine migration is a life stage with high mortalities, due to both natural and human influences. Factors affecting mortality during the smolt and post-smolt stages contribute to determine the abundance of spawner returns. With many S. salar populations in decline, increased mortality at these stages may considerably contribute to limit S. salar production, and the consequences of human-induced mortality at this stage may be severe. Development of management actions to increase survival and fitness at the smolt and post-smolt stages is crucial to re-establish or conserve wild populations.

Envisioning the future of aquatic animal tracking: Technology, science, and application. BioScience, 67(1): 884-896 is available online at: https://doi.org/10.1093/biosci/bix098. Additional information:Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Electronic tags are significantly improving our understanding of aquatic animal behaviour and 47 are emerging as key sources of information for conservation and management practices. Future 48 aquatic integrative biology and ecology studies will increasingly rely on data from electronic 49 tagging. Continued advances in tracking hardware and software are needed to provide the 50 knowledge required by managers and policy makers to address the challenges posed by the 51 world's changing aquatic ecosystems. We foresee multi-platform tracking systems for 52 simultaneously monitoring position, activity, and physiology of animals and the environment 53 through which they are moving. Improved data collection will be accompanied by greater data 54 accessibility and analytical tools for processing data, enabled by new infrastructure and 55 cyberinfrastructure. To operationalize advances and facilitate integration into policy, there must 56 be parallel developments in the accessibility of education and training as well as solutions to key 57 governance and legal issues. 58 59

Knowledge of the prevalence of escaped farmed fishes in the wild is an essential first step to assessing the risk resulting from interactions between farmed and wild fishes. This is especially important in eastern North America, where Atlantic salmon ( Salmo salar ) aquaculture occurs near wild Atlantic salmon rivers and where many wild salmon populations are severely depressed. Here, we review the literature on the incidence of escaped farmed salmon in eastern North American rivers, for which there has been no comprehensive compilation to date. Escaped farmed salmon have been found in 54 of 62 (87%) rivers investigated within a 300 km radius of the aquaculture industry since 1984, including 11 rivers that contain endangered salmon populations. Averaged among all investigations, the proportional representation of farmed salmon among adults entering the rivers from the sea was 9.2% (range 0% to 100%). Where data were sufficient to examine temporal trends, farmed salmon proportions varied considerably over time, suggesting that escape events are episodic in nature. We conclude that escaped farmed salmon are sufficiently prevalent in eastern North American rivers to pose a potentially serious risk to the persistence of wild salmon populations, especially in those rivers that are adjacent to existing aquaculture sites.

The migration dynamics and inter-annual variation in early at-sea survival of Atlantic salmon (Salmo salar) smolts over 14 years of study are reported for four river populations located in the Gulf of St. Lawrence (Canada). Acoustically tagged smolts were monitored at three points along their migration from freshwater to the Labrador Sea, a migration extending more than 800 km at sea and a period of 2 months. A hierarchical state-space version of the Cormack–Jolly–Seber model was used to estimate apparent survival rates from incomplete acoustic detections at key points. There was a positive size-dependent probability of survival through the freshwater and estuary areas; the odds of survival of a 16 cm smolt were 1.5–1.7 times higher than for a 13.5 cm smolt, length at tagging. Length adjusted (centred to the mean fork length of smolts during the study of 14.6 cm) survivals through the estuary and nearshore waters were estimated to range between 67 and 90% for the two river populations migrating through Chaleur Bay in contrast to lower survival estimates of 28–82% for the two populations from the neighbouring Miramichi Bay. Across the 14 years of study, survival estimates varied without trend for the populations of Chaleur Bay, but declined for the populations migrating through Miramichi Bay. Survival through the Gulf of St. Lawrence was variable but generally high among years and rivers, ranging from 96% day−1 to 99% day−1. Long term, replicated studies at multiple sites using acoustically tagged smolts can provide empirical data to examine hypotheses of the location and timing of factors contributing to smolt and post-smolt mortality of salmon at sea.

Over the last decade, goldfish Carassius auratus L., have been introduced into lakes and ponds in the Montreal region. Controlled experiments compared the impact of goldfish in both mudand gravel-bottomed outdoor pools, with either caged or non-caged vegetation. High levels of turbidity were generated by foraging goldfish in mud pools (P<0·01). All non-caged submersed plants (Potamogeton) showed extensive grazing damage and all of the unprotected submersed and emergent forms were uprooted. Data from Stoneycroft pond where a feral goldfish population reached 15-17 000 individuals ha 1 , confirmed the experimental findings showing goldfish to be benthic herbivores, causing a visible increase in turbidity and decrease in aquatic vegetation. Gut analysis revealed goldfish to have little diet overlap with native amphibians. High turbidity should reduce the success of predators feeding on goldfish, and may decrease the foraging success of other competitors. The sporadic distribution of goldfish in Canada may be linked to site characteristics, specifically the susceptibility of the area to turbidity generation. 1995 The Fisheries Society of the British Isles

We examined the effects of ambient temperature (10, 20, and 30 °C) and relative humidity (10, 50, and 95% RH) on the aerial exposure tolerance of adult zebra mussel (Dreissena polymorpha) and quagga mussel (D. bugensis) collected from the St. Lawrence River. Survivorship of mussels in air significantly increased with increasing RH, decreasing temperature, and increasing mussel size. At 20 °C and 50% RH (early temperate summer conditions), large (21–28 mm) D. polymorpha survived more than 5 days exposure, whereas small (10–18 mm) D. polymorpha survived 1–3 days. Seventy-three percent of large D. polymorpha and 10% of small D. polymorpha survived 10 days exposure at conditions considered optimal for survivorship (10 °C and 95% RH). Survivorship of D. bugensis was tested at 20 °C and was 15–100% lower than that of D. polymorpha at all RH levels combined with exposures less than 5 days. Dreissena bugensis also suffered significantly higher percent weight losses because of desiccation than D. polymorpha. The differences in the desiccation tolerance of zebra and quagga mussels reflect their relative depth distribution in lakes. Our results suggest that, given temperate summer conditions, adult Dreissena may survive overland transport (e.g., on small trailered boats) to any location within 3–5 days' drive of infested waterbodies.

Migration is a widespread but highly diverse component of many animal life histories. Fish migrate throughout the world's oceans, within lakes and rivers, and between the two realms, transporting matter, energy, and other species (e.g., microbes) across boundaries. Migration is therefore a process responsible for myriad ecosystem services. Many human populations depend on the presence of predictable migrations of fish for their subsistence and livelihoods. Although much research has focused on fish migration, many questions remain in our rapidly changing world. We assembled a Lennox et al. Fish Migration Questions diverse team of fundamental and applied scientists who study fish migrations in marine and freshwater environments to identify pressing unanswered questions. Our exercise revealed questions within themes related to understanding the migrating individual's internal state, navigational mechanisms, locomotor capabilities, external drivers of migration, the threats confronting migratory fish including climate change, and the role of migration. In addition, we identified key requirements for aquatic animal management, restoration, policy, and governance. Lessons revealed included the difficulties in generalizing among species and populations, and in understanding the levels of connectivity facilitated by migrating fishes. We conclude by identifying priority research needed for assuring a sustainable future for migratory fishes.

Observations of male three-spined stickleback (Gasterosteus aculeatus L.) parental care were made in a salt-marsh tide pool at 3-h intervals over 24-h cycles, to determine if male behavior varied in association with diel changes in water temperature and dissolved oxygen concentration. An analysis of egg metabolism in situ revealed positive correlations between rate of egg oxygen consumption and egg age, water temperature, and dissolved oxygen levels, while there was a slight but significant negative correlative with the number of eggs per nest. We found no significant difference when we compared the proportion of time males spent fanning their nests during the day with night levels. However, nocturnal fanning bouts were significantly longer and less numerous than diurnal ones. In contrast to the rest of the 24-h cycle, the males remained inactive between fanning bouts at night, except when exposed to hypoxic conditions