The Control of Fish Migration

Fish migration is important and spectacular. Migratory fish gather energy in one portion of the environment and transport it to other areas, where it often becomes available to humans or to other elements in the ecosystem. Migration brings fish into situations that allow easy harvest as they concentrate along migration routes. Their journeys also make them vulnerable to human intereference at critical points along their route. Salmon, for example, may harvest plankton in the open ocean and transport that food energy to coastal and inland regions, where it is captured by fisheries or deposited in inland streams and utilized by the flora and fauna of the region. These salmon are able to complete journeys of thousands of kilometers from their natal streams to oceanic feeding grounds and back to the same home streams, an accomplishment that strains our credi bili ty . We now understand some of the timing and guiding stimuli used in these migrations, and mechanisms can be logically proposed, on the basis of the established abilities of fishes, to account for the unexplained portions of the migrations. There is no single factor guiding these fish. Instead, they are dependent on the presence in their environment of a great variety of appropriate orienting and timing stimuli. These stimuli are vulnerable to human interference. The more widespread and easily available the information on these requirements, the more readily fish can be protected from such interference.

Contenu

1. Introduction.- 2. Light.- 2.1 Light in Water.- 2.2 Fish Photoreceptors.- 2.3 Timing.- 2.4 Direction and Distance.- 2.5 Summary.- 3. Chemical Information.- 3.1 Characteristics and Importance of Chemical Information in an Aqueous Environment.- 3.2 Fish Chemoreception.- 3.3 Timing by Chemical Stimuli.- 3.4 Direction and Distance.- 3.5 Summary.- 4. Mechanical Stimuli.- 4.1 Mechanical Stimuli.- 4.2 Mechanoreceptors.- 4.3 Mechanoreception and Timing.- 4.4 Mechanical Direction and Distance.- 4.5 Summary.- 5. Temperature.- 5.1 Introduction.- 5.2 Temperature Reception.- 5.3 Timing by Thermal Stimuli.- 5.4 Thermal Stimuli Controlling Direction and Distance.- 5.5 Summary.- 6. Electrical and Magnetic Stimuli.- 6.1 Electricity in Water.- 6.2 Electroreception.- 6.3 Electrical Timing.- 6.4 Electrical Stimuli Affecting Direction and Distance of Migration.- 6.5 Magnetism.- 6.6 Magnetic Senses.- 6.7 Magnetic Timing.- 6.8 Magnetic Stimuli and Direction and Distance.- 6.9 Summary.- 7. The Past: Learning and Genetics.- 7.1 Learning.- 7.2 Genetic Differences Between Fish Stocks.- 7.3 Genetic Control of Timing of Migration.- 7.4 Genetic Control of Migratory Direction.- 7.5 Summary.- 8. Conclusion.- References.- Systematic Index.