Q:Please help settle a long-standing debate. Why are some sharks good to eat (like the mako) and most others inedible? I've maintained that the edible species tend to be the so-called "warm-blooded" ones. Is this the case?
-- Don Dietrich
Nyack, New York
A: Don, the mackerel sharks (family Lamnidae), which include the white (Carcharodon carcharius), longfin and shortfin makos (Isurus spp.), and porbeagle (Lamna nasus), have body temperatures substantially higher than those of their environments that still vary as water temperatures change. These heterothermic sharks are among the best to eat, although the muscle of white sharks has been reported to be toxic. Some sharks that do not possess elevated body temperatures can be good eating as well. These include the spiny dogfish (Squalus acanthiasacanthias), the threshers (Alopias spp.), and the blacktip (Carcharhinus limbatus).
Sharks store metabolically derived compounds in their blood, helping maintain proper ion and water balances; the best-known of these are urea and trimethylamine oxide (TMAO). These compounds, as well as others formed during decomposition, can produce an undesirable taste in shark meat and, in the case of TMAO, can even form a toxic byproduct (this is particularly well-known in the Greenland shark, Somniosus microcephalus.) Because of the disagreeable taste produced by these compounds, any shark destined for human consumption must be properly prepared and stored immediately after capture. Although little research has been done on this topic, it appears that certain species taste good while others don't due to the quantitative (amount) and qualitative (type) differences of the compounds in their tissues.
- Ray Waldner