Shark Info Logo


Shark Info 2 / 99   (06-15-1999)

Author

  Intro:

Underwater Parks

Shark Info

  Main article:

Underwater Parks: Economic and Ecological Aspects

Shark Info

  Article 1:

Jeopardized ┬źNurseries┬╗

Dr. T. E. Hopkins

  Article 2:

Requiem for smoked dogfish

Dr. A. J. Godknecht

  Article 3:

Aggressive Sharks, reality or fantasy?

Dr. E. K. Ritter

  Fact Sheet:

Spiny Dogfish

Dr. E. K. Ritter


Jeopardized "Nurseries"

By Dr. Todd E. Hopkins

During their more than 400 year evolution, sharks had practically only one enemy - larger sharks. Small and newborn sharks are especially endangered. At the end of their pregnancy, shark females return to the shallow bays where they were once born in order to bear their young. Here their offspring are protected from being eaten by larger sharks and also enjoy rich feeding grounds. These shark "nurseries" are not only hard to access for larger sharks but also form a secure port for shark pups or other smaller shark species.

Joung shark

Young lemon shark searching for food in shallow waters.

© Shark Info

Very often the youngsters can be observed along the shore, only about half a meter below the surface, searching for food in the form of small fish and crabs. As the pups grow larger, they expand their territory to deeper waters in search of larger prey. With the first winter approaching, the young sharks usually migrate to warmer waters or regions where more food is available. Most large- or small-sized sharks live off the continental shelf, often as close as approximately 10 km off the coast.

Sharks belong to the most successful ocean vertebrates, and their choice of breeding grounds supports their success quota. However, precisely this behavior of selecting the flat coastal regions for their nurseries may become the very reason for their destruction, for man has developed into the most destructive force to ever threaten shark nurseries in their long evolutionary development.
Almost 60% of all humans live within a radius of 60 km from the coast. The so-called development of entire coastal regions and resulting changes to the watersheds have either destroyed or irreparably altered significant habitats for shark females and their young. Man reduces the water levels of rivers for the purpose of drinking, irrigation and golf areas. We misuse rivers as a cheap means of transportation to conduct our garbage and industrial pollutants into the ocean, and by so doing ruin the water quality, reduce the water flow and change the natural cycles in which the water flows into rivers and bays.

Sharks have undergone more than 400 million years of evolution, a long and successful adaptation to natural cycles which is essentially why they have problems in adapting to "recent" changes which only occurred in the last couple of centuries. Does this mean that an evolution which took millions of years to develop is now suddenly bad? Only man has really developed such flexibility.

Sharks are an integrated and important component of our coastal ecosystems. As top and even super hunters, they control the natural balance of the fish populations. Natural, unspoiled habitats, especially the "nursery regions", represent basic prerequisites for reproduction, healthy growth, migration and in general the survival capabilities of most sharks. However, even if sharks grow up in naturally intact and clean breeding grounds, they are still endangered when migrating. During their migrations they inadvertently cross various political boundaries and national fishing zones with often very different fishing regulations.

When young sharks are born in a given country, it is entirely possible that they may be caught and killed either as juveniles or fully grown sharks as they pass through the territorial waters of another country. This can lead to a significant reduction of protected or even unprotected populations. Such mechanisms were observed in the eighties, as described by Terry Walker (1996) and Robert E. Hueter (1998), along the coast of Natal, South Africa, and along the Florida coastline. Port Phillip Bay in Australia is another sad example of the probably irreversible decimation of a shark population. In the 1940s the dogfish, Galeorhinus zyopterus or soupfin shark was quite heavily fished by local fishermen. In fact the number of dogfish caught tripled between 1942 and 1944. Shortly thereafter the catches collapsed radically and remaining populations were protected by a procedure called "minimum catch length". Since that time, fishermen from Port Phillip Bay only rarely catch a dogfish and the Victorian Fishery Institute estimates that the dogfish population in the bay has shrunk to about 25% of the estimated population around 1920.

How can we ensure that shark breeding areas are not destroyed and further populations endangered? One possibility is to restore coastal breeding areas to their natural condition and find ways to protect these areas. We must convince politicians that coastal bays must remain intact and that certain regions must be declared as parks and nature reserves for fish and sharks. The uncontrolled exploitation of shark populations must be stopped as soon as possible, while safeguards should be established to maintain the natural habitats where sharks and fish live, migrate and reproduce. Governments must be convinced that ecological considerations have economic validity. They must be ready to support the risk of policies, which in case of doubt - and without large-scale studies - decide in favor of the environment. If in doubt every meter of coastline is worth protection.

This will not be an easy process, for revitalizing coastlines is expensive, although by no means unknown. In Southwest Florida the government bought back 280,000 hectares of the most western part of the Everglades for more than 25 million dollars for purposes of revitalization. According to the report made by Luther J. Carter titled "The Florida Experience - South Florida: The problems of Growth", the economic exploitation of some areas turned out to be dismal failures. This repurchased land should thus never again be sold or built over. While the site is currently in dismal condition, it should be reverted back to its original condition of about 30 years ago, based on the official plan titled the "Hydrologic Restoration of Southern Golden Gate Estates". I am convinced that this important region for fish and sharks can be protected and restored to its original pristine condition. The appropriate technologies and methods are available. However, people must now be convinced to change both their daily routines and associated economic practices in order to reach this objective.

    * Dr. Todd E. Hopkins is research coordinator in the Office for Environmental Protection in Florida, USA, and for Rookey Bay, the national estuary research reserve. He studies the effects of economic restoration of coastal zones, including the impact on water quality and coastal species of fish and sharks.

    Die Hai-Stiftung unterstützt ein Projekt von Dr. T. Hopkins in Rookery Bay / Ten Thousand Islands an der Ostküste Floridas. Das Projekt hat zum Ziel, die Langzeitwirkung der Wiederherstellung eines bisher künstlich regulierten Abflusses der Everglades (Wasserscheide) auf die dortigen Hai-Kinderstuben zu untersuchen.

May be published only by indicating the source: Shark Info / Dr. Todd E. Hopkins



  top

 

last change: 06-04-2016 10:48