Neil Hammerschlag, PhD

Ecology, Distribution & Eco-Toxicology of South Florida’s Sharks

The delineation and characterization of habitat significant to the life-history and ecology of sharks has been identified as one of the highest priorities for their conservation. Little is known about the ecology of Southeast Florida’s shark fauna. Despite this, shark fishing pressure along the coast remains high. Thus, there is a need to appropriately document Southeast Florida’s coastal shark fauna, determine their relative abundance and attempt to identify habitat which may be important for their survival so that appropriate management actions can be taken if necessary.

Under the aegis of the South Florida Student Shark Program (SFSSP), sharks surveys are currently being conducted in Biscayne and Florida Bay to determine the relative distribution, abundance and movements patterns of Southeast Florida’s coastal shark species. In addition, research is being conducted to identify specific habitats where sharks maybe susceptible to bioaccumulation of toxins, such as mercury.

Additionally research is being conducted in collaboration with Dr. Deborah Mash (University Medical School) and Dr. Larry Brand (University of Miami Rosenstiel Marine School) to study the presence of deadly neurotoxins in shark fins linked to prevalent and severe human neurodegenerative diseases (such as dementia of the Alzheimer's type and ALS), which as of yet have no cure.

This work has potential for broad impact because if these toxins are found it sharks it would suggest a possible route of human exposure through the marine environment. Moreover, anthropogenic pollution may increase the risk of widespread human neurotoxin exposure through the marine food chain. The results of this investigation will also be valuable for informing the public about the potential danger of consuming shark products and for the establishment of policies to enact and enforce bans on shark finning.

White Shark Predatory Behavior

Brief Overview

NOTE: The Seal Island work described below reports on over 2,500 natural predatory attacks by white sharks on Cape fur seals. It is a shared result of an 8-year collaboration among R. Aidan Martin, the principal investigator of this project, Chris Fallows & Rob Lawrence, South African naturalists who discovered and opened the Seal Island site, and myself, with the gracious help of other people, as cited in context.

During the winter, white sharks visit Seal Island to predate on Cape fur seals. About 48% of surface attacks on Cape fur seals result in successful kills. Attack frequency is high, averaging 6.68 per day, with as many as 43 recorded in a single day. Sharks attack seals on the surface via a sudden vertical rush, which propels predator and prey out of the water in an awesome display of power and acrobatic prowess. White sharks appear to hunt solitary juvenile Cape fur seals near their primary entry and exit point early in the morning, when light levels are low. Stalking is conducted from near the bottom, from sufficient depth to remain undetected during approach, and the attack launched vertically. This strategy maximizes a shark's chance of catching a seal unaware, resulting in a fatal or incapacitating initial strike. Stealth and ambush are key elements in the white shark's predatory strategy. Further, recognizable individual white sharks display distinct predoatry strategies and some enjoy a predatory success rate of roughly 80%.