A variety of movements characterize the behavioral plasticity of Atlantic salmon (Salmo salar) in fresh water, including movements of fry from redds, establishment of feeding territories, spawning ...

http://www.bio.umass.edu/biology/mccormick/pdf/cjfas%2098%20movement,%20migration%20and%20smolting.pdf

Movement, migration, and smolting of Atlantic salmon (Salmo salar)

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.

/pdf/a-critical-life-stage-of-the-atlantic-salmon-salmo-salar-uj6jstbc0n.pdf

A critical life stage of the Atlantic salmon Salmo salar: behaviour and survival during the smolt and initial post-smolt migration.

Remote sensing technologies have been used to study the behaviour and movements of fish in the sea for about 30 years. The first relatively simple devices have given rise to a suite of sophisticated tools that have spawned a whole new field of fisheries science. The oldest method, acoustic telemetry, has now advanced to the level at which we can study detailed behaviour in the field in relation to the immediate environment, and monitor physiological variables, as well as document larger-scale movement patterns. Archival tags, available for the last 7–8 years, provide a powerful tool to obtain detailed information on a range of variables for large number of individual fish over long periods of time. Their primary limitation is that they must be recovered to obtain the data. The most recent development, the pop-up satellite tag, requires no recovery and can thus be used on any fish of sufficient size. Being fully independent of the fisheries, this type of tag is ideal for studying large, highly migratory fish and dramatically expands the scope of questions that can be addressed. The pace of technical development will undoubtedly continue to accelerate over the next few decades, producing new tools that can be expected to solve many currently unanswered questions in fisheries biology. Solutions to these questions should help to achieve improved management of the seas and their living resources.

Electronic Tags in Marine Fisheries Research: A 30-Year Perspective

The effects of intraperitoneally implanted dummy acoustic transmitters on juvenile Atlantic salmon Salmo salar of comparable size to wild presmolts and smolts were examined in two laboratory experiments. In the first experiment, different-sized tags (24, 28, and 32 mm × 8-mm diameter) that mimicked acoustic transmitters suitable for long-term studies were assessed. There was 60% mortality (3 of 5 fish) with the 32-mm implant early in the 316-d study and 20% mortality (1 of 5 fish) with the 28-mm implant. All fish surviving with 28- and 32-mm implants eventually expelled their tags, compared with only 20% of fish (1 of 5) with the 24-mm implant. Tag expulsion was not a cause of death. After implantation, tags were first encapsulated in a thick membrane and then expelled between 142 and 217 d after surgery, exiting at a site where pressure of the tag on the abdominal wall was greatest. Growth of tagged fish was initially delayed and lagged that of control and sham-tagged fish, but survivors from th...

Effects of Implanted Dummy Acoustic Transmitters on Juvenile Atlantic Salmon

The effect of atrazine on Atlantic salmon (Salmo salar) smolts in fresh water and after sea water transfer.

Thirty-two wild Atlantic salmon (Salmo salar) smolts, tagged with miniature acoustic transmitters, were tracked in the River Conwy, North Wales, to describe the freshwater and estuarine patterns of...

A. Moore

Papers

The migratory behaviour of wild Atlantic salmon (Salmo salar) smolts in the estuary of the River Conwy, North Wales