Fish Migration 2 Flashcards
Fish migrations pose huge bioenergetic and navigational challenges:
Extensive distances (1000’s km)
Diverse environments (temperature, depth salinity etc.)
Precise homing to natal areas
Predictions of the olfactory hypothesis:
(1) streams possess unique and temporally stable chemical characteristics
(2) salmon have the ability to detect and distinguish these differences
(3) salmon learn the chemical characteristics of their natal stream, remember them and respond to them as adults
The importance of olfaction in homing of salmonids:
First proposed by Halser and Wisby (1951); intensively researched since then. It is now accepted that specific odours in natal stream are important for olfactory imprinting in juveniles and localised homing in adults.
What is homing accuracy
By homing to the exact location where they hatched fish deliver their offspring to the environmental conditions to which they are likely to be best adapted
Why would fish stray to non-natal sites
By straying to non-natal sites to spawn, fish can widen their distribution and avoid deleterious effects of inbreeding/reduced genetic diversity
example of fish straying from natal waters
humpback salmon show the highest levels of straying, are the most widely distributed and have the largest populations.
Challenges in salmon migrations
In recent decades survival of Atlantic salmon at sea has declined dramatically
Linked to declines in growth
- Explanation?
- Climate change?
- Naturally driven regime shift?
- Disease/parasitism?
A better understanding of the distribution and movements of salmon during the marine phase is needed to explain these trends and improve stock forecasting and management
Whats DFAA
Dissolved free amino acids.
Induce an olfactory response in the olfactory epithilium of masu salmon (O. Masou) (Shoji et al 2000)
How do sockeye salmon migrate to localised homing
Authors propose that salmon use visual cues at larger distances (>1km) from natal area and use olfactory cues at closer range (<1km). Magentic cues did not appear to be important
How do sockeye react when imprinted natal cues are absent
Sockeye salmon are attracted to conspecifics when imprinted natal cues are absent, but not when they are present.
Sockeye salmon are attracted to conspecifics when imprinted natal cues are absent, but not when they are present.
What is PST
parr-smolt transition. Its when imprinting occurs.
When salmon are exposed to an odour as embryos, parr or smolts that seems to help them migrate to homing waters when adults.
What migration habits do species have when they leave their natal site before PST
imprinting may occur earlier; hatchery-reared kokanee salmon imprint on artificial odorants at the end of embryonic development when they would typically emerge from their gravel nest and migrate to a lake (Tilson et al. 1994, 1995).
What migration habits do salmon exposed to scented odours in water when smolts
Only salmon exposed as smolts were attracted as adults to water scented with same odour (Dittman et al. 1995).
Salmon reared at one site but released from a second site prior to, or during, PST return as adults to the release site, not the rearing site (Jensen and Duncan, 1971).
What drives imprinting
Thyroid hormones thought to play an important role:
In Atlantic salmon (Salmo salmar) a period of increased thyroid activity during the PST coinicides with enhanced olfactory sensitivity and imprinting ability (Morin and Doving,
1992)
What is SOIG
Olfactory system Imprinting related Gene
