The early migration and spawn timing of hatchery fish were believed to effectively prevent them from interbreeding with wild fish.
Thus, migration and spawn timing of hybrids would be expected to overlap with the timing of both populations.
Some of these populations have discrete patterns of migration and spawn timing [ 23, 24], which adds a temporal dimension to spatial divergence [ 46].
Ample evidence shows that much of the variation in migration and spawn timing in salmonid fishes is attributed to additive genetic variation (Carlson and Seamons 2008).
The specific aim of this study was to determine whether segregation based on differences in migration and spawn timing prevented hybridization of hatchery fish and wild fish and minimized ecological impacts by preventing natural propagation of hatchery fish.
Altering natural flow systems can lower water tables, increase saltwater intrusion to coastal areas, and harm fish migration and spawning, it said.
The report said warming sea temperatures were related to changes seen in the depth, distribution, migration and spawning behaviours of fish.
Using passive integrated transponder (PIT) telemetry, this study evaluated the efficacy of two such conventional, technical fishways (pool and weir and plain Denil baffle) located on the Yorkshire River Derwent, north-east England, for the threatened anadromous European river lamprey Lampetra fluviatilis, an anguilliform swimmer, over the upstream migration and spawning seasons.
Over the past decade, however, environmentalists have targeted dams as outmoded, inefficient energy providers with serious impacts on water flow, surrounding and downstream environment, species migration and spawning, sediment collection, algae blooms, and other damage to the natural process.
Last spring, Britain's Marine Climate Change Impacts Partnership, which unites a wide array of scientists, government agencies and industries, issued an analysis that found "clear changes in the depth, distribution, migration and spawning behaviors of fish -- many of which can be related to warming sea temperatures".
However, southern coastal cod accumulated a higher number of degree days prior to migration and spawning than frontal fish in the same region (F1,61 = 61.86; P≤0.0001).
