*Migration in fishes* refers to the seasonal or periodic movement of fish from one location to another. This movement can be for various reasons such as breeding, feeding, or avoiding unfavorable environmental conditions.
*Types of Migration in fishes:*
Fish migration can be classified into several types based on the direction and purpose of movement:
1. Anadromous Migration: Fish move from the ocean or sea into freshwater rivers or streams to spawn. Examples include salmon and sturgeon.
2. Catadromous Migration: Fish migrate from freshwater to the ocean or sea to spawn. Eels are a common example of catadromous fish.
3. Potamodromous Migration: Fish migrate within freshwater systems, typically moving upstream or downstream within rivers or streams. Trout and some species of freshwater catfish exhibit potamodromous migration.
4. Oceanodromous Migration: Fish migrate within the ocean, often for feeding, breeding, or seasonal changes in temperature. Tuna, sharks, and some species of mackerel are examples of oceanodromous migratory fish.
5.Diadromous Migration: Fish migrate between freshwater and saltwater environments at different stages of their life cycle. This category includes both anadromous and catadromous migrations.
*Factors influencing fish migration*
Several factors influence fish migration:
1. Environmental Conditions: Changes in temperature, water flow, salinity, and oxygen
levels can trigger migrations as fish seek optimal conditions for breeding, feeding, or survival.
Temperature has a pervasive effect on the physiology of animals and will thereby impact population movement and growth. Thermal physiology should therefore be included in management plans, for both conservation and fisheries. Little et al.,2020
2. Feeding Opportunities: Fish may migrate in search of abundant food sources, especially during seasonal fluctuations in prey availability.
3. Habitat Quality: Degradation or alteration of habitats due to human activities can disrupt migration routes or reduce the availability of suitable spawning grounds, influencing fish migration patterns.
4. Predator Avoidance: Fish may migrate to avoid predators or unfavorable conditions, such as low dissolved oxygen levels or high turbidity, that can increase vulnerability to predation.
5. Life Cycle Changes: Different life stages of fish may require specific habitats or environmental conditions, leading to migrations between freshwater and marine environments or within freshwater systems.
6. Physical Barriers: Natural obstacles like waterfalls or man-made structures such as dams can obstruct migration routes, forcing fish to alter their behavior or seek alternative pathways.
7. Social Interactions: Social cues, such as the presence of conspecifics or competition for resources, can influence fish behavior and migration patterns.
8. .Reproductive Needs: Many fish species migrate to spawn in specific habitats where offspring have better chances of survival. Changes reproductive hormone.
3. INTRODUCTION
TYPES OF MIGRATION IN FISHES
FACTORS INFLUENCINGFISH
MIGRATION
MECHANISMOF FISH
MIGRATION
METHODS TO STUDY FISH
MIGRATION
CASE STUDIES
CONSERVTIONAND
MANAGEMENT OF MIGRATORY
FISH SPECIES
13. Case Studies
Figure 6: Salmon migration
https://images.squarespace-
_WmhRsMRoXaKPI_am2d/SalmonCycle_new2
-1020x680.jpg
14. Conservation and Management
of Migratory Fish Species:
a. Habitat restoration:
b. Fish passage structures:
• Riparian zone protection
• Wetland
conservation
• Barrier removal
