White shark (Carcharodon carcharias) COSEWIC assessment and status report: chapter 8
Limiting Factors and Threats
Humans are the most significant predators of white sharks, taking largely unmonitored numbers as sport fish and commercial bycatch as well as targeting them for their lucrative jaws, teeth, and fins (Compagno et al. 1997). Markings found on stranded white sharks in the Queen Charlotte Islands, British Columbia (Figure 3a), suggest that mortality may have resulted from fisheries bycatch (R.A.Martin-author, unpublished data), but there are no confirmed records of any white shark being caught by fishing gear in Canada’s Pacific waters.
Sixteen of 32 (50%) of white shark records from Atlantic Canada are accidental captures as bycatch (present study). The white sharks’ tendency to investigate boats and other floating objects often brings them to the surface, where they can be easily hooked, shot, or harpooned.
As long-lived, apex predators, one would expect white sharks to bioaccumulate pollutants in their tissues. Zitko et al. (1972) found that muscle and liver tissue from white sharks taken in the Bay of Fundy-Gulf of Maine area had higher levels of PCBs and chlorinated hydrocarbon pesticides than other fishes. Note, the health impacts of these toxins have not been investigated in elasmobranchs, however – given the fragility of spermatozoa and the well-documented feminizing influence of organochlorides – it seems likely to negatively impact reproductive fitness of males, possibly via compromised gametogenesis or impaired sperm motility (Cadbury 1997).
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