Background on Sharks

Sharks keep our oceans in balance, and so without them ecosystems fail. Sharks deserve our respect and stewardship, and that is why it’s so important for everyone — including anglers, the public, local municipalities, and policy-makers — to advocate for sharks by staying informed on current regulations and best fishing practices for safe catch and release.  

MOST shark species are:

  • slow-growing and take many years to reach sexual maturity
  • known to give birth to relatively few young
  • apex predators: at the top of the food chain
  • threatened due to overfishing

ALL sharks species are:

  • ecologically important; a change to their numbers can impact the stability of other local fish populations

Their plight:

Globally, humans collectively kill at least 63 million and as many as 273 million sharks each year. This is both a staggering and unsustainable number, and subsequently many shark species are now threatened or even critically endangered. 

Sharks are in peril due to:

  • Overfishing and bad fishing practices. Overfishing occurs when fish are caught at such a high rate that the breeding population is unable to recover, depleting the population. Read the World Wildlife Fund's assessment here.
  • Shark finning. This is the act of cutting fins off of living sharks, keeping those fins for sale, and discarding the still-living, but wounded shark back into the water. Read a Smithsonian article about it here.
  • Bycatch. This refers to species that are unintentionally caught and subsequently killed by fishing gear (longlines, trawls, gillnets). Read an Oceana article here.
  • Loss of coastal habitats for their young. Juveniles of many shark species depend on specific coastal habitats for survival during their first couple of years, when they are most vulnerable. Read a Save our Seas report here.

 Read more about threats to sharks and conservation efforts underway here.

What makes Sanibel-Captiva a special place for sharks, and why are they important here?

  • We have excellent mangrove habitat for juvenile sharks; we have year-round residents as well as migratory species and relatively healthy food sources. 
  • High nutrient input from numerous rivers throughout the watershed fuel the lower trophic levels, quickly affecting the entire food web.
  • Sharks and seagrass work for each other:
    • Seagrass is a good habitat for many crab species, which in turn are a good food source for sharks. 
    • Sharks indirectly maintain seagrass habitat. As sharks rove, they keep many species of grazing animals at bay. Without sharks disturbing grazers in this way, the grazers could decimate seagrass beds (NSF, Oceana).
  • Sharks and freshwater discharges from the Caloosahatchee River:
    • Some sharks, such as the Bull Shark, can survive in freshwater, while others cannot. Therefore, changes in the salinity levels of the Caloosahatchee River will determine which shark species have access to the river, along with the resources it affords. 
    • Toxic algae growth that results from overly nutrient-rich water affects shark health, and so eutrophic waters coming down the Caloosahatchee are of great concern.   


Photos: Michael Timm