Tagging and Migration
How Do Sharks Migrate?
What Does Tagging Have To Do With Migration?
Shark Tagging Learning Activity
What Factors Cause Shark Migration? As with salmon, geese, and other animals, many sharks also migrate. There are three major factors that cause shark migration. Whether sharks migrate or not depends to a large degree on temperature and seasonal changes, reproduction, and food sources.
Sharks, like many other animals, migrate for purposes of mating and giving birth. These migrations are timed by seasons of the year, which cause water temperature changes that may trigger sharks to migrate to their breeding and pupping grounds. The sandbar shark is one specie that migrates to breeding grounds to reproduce.
The sandbar shark, for example, is found in large numbers off the east coast of Florida, in spring. This is a major mating ground for the shark. Sandbar sharks migrate north in early summer, and females move into northeastern bays and estuaries in June to have their pups. Delaware Bay is a major pupping ground for sandbar sharks. Throughout the summer months, from June to early September, the pups will remain in the relative safety of these bays and estuaries and will then migrate south as winter approaches. Adult sandbar sharks will continue their migration northward after pupping season and will move south for the winter as water temperatures begin to cool.
Another primary cause of animal migrations is availability of food sources. Movements of fish which sharks prey on will cause the sharks to follow in pursuit. Often, the movements of food fish are related to water temperature changes similar to those that factor in shark migrations. Seasonal availability of marine mammals also factors in migration patterns of those species of sharks that feed upon them. For example, great white sharks reach the northernmost parts of their range in summer. Along the eastern Pacific ocean, this area extends up to the southern Alaskan islands. In early spring, the sharks have returned to the coast of California. In April, they arrive at the Farallon Islands and Ano Nuevo Island off the coast of the San Francisco Bay to feed on seals. In mid to late April the sharks migrate to the Channel Islands off the coast of Los Angeles, to have their pups, and in May, the sharks return to Ano Nuevo and the Farallons to feed on elephant seal pups that were born in the early spring. Elephant seal pups are very high in fat and are an excellent food source for great white sharks.
One very significant factor affecting shark migration and navigation is the shark's sensitivity to water temperature. As the seasons change, many species migrate in order to stay within their preferred water temperature range. Most sharks are cold-blooded (their internal body temperature is the same as the outside water temperature), so they will migrate to stay within their preferred temperature ranges. Some sharks prefer warm temperatures and will spend much of their time in tropical waters. Other sharks, such as the great white shark and the shortfin mako shark have a higher metabolic rate, which allows them to generate their own heat. These sharks have a wider range of movement, and are able to withstand lower water temperature ranges. Water temperature changes also affect the movements of fish and other food sources. Therefore, sharks may migrate to pursue food that prefers a certain temperature range. Through tagging and recapture research, scientists are able to associate different temperature ranges with different species of sharks, following their migrations from one location to another.
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