More than just baby sharks

23 04 2009

Sharks worldwide are in trouble (well, so are many taxa, for that matter), with ignorance, fear, and direct and indirect exploitation (both legal and illegal) accounting for most of the observed population declines.

Despite this worrisome state (sharks have extremely important ‘regulatory’ roles in marine ecosystems), many people have been slowly taking notice of the problem, largely due to the efforts of shark biologists. An almost religious-like pillar of shark conservation that has emerged in the last decade or so is that if we save nursery habitats, all shark conservation concerns will be addressed.

Why? Many shark species appear to have fairly discrete coastal areas where they either give birth or lay eggs, and in which the young sharks develop presumably in relative safety from predators (including their parents). Meanwhile, breeding parents will often skip off as soon as possible and spend a good proportion of their non-breeding lives well away from coasts. Sexual segregation appears to be another common feature of many sharks species (the boys and girls don’t really play together that well).

The upshot is that if you conserve these more vulnerable ‘nursery’ areas in coastal regions, then you’ve protected the next generation of sharks and all will be fine. The underlying reason for this assumption is that it’s next-to-impossible to conserve entire ocean basins where the larger adults may be frolicking, but you can focus your efforts on restricted coastal zones that may be undergoing a lot of human-generated modification (e.g., pollutant run-off, development, etc.).

However, a new paper published recently in Conservation Letters entitled Reassessing the value of nursery areas to shark conservation and management disputes this assumption. Michael Kinney and Colin Simpfendorfer explain that even if coastal nurseries can be properly identified and adequately conserved, there is mounting evidence that failing to safeguard the adult stages could ultimately sustain declines or arrest recovery efforts. The authors support continuing efforts to identify and conserve nurseries, but they say this isn’t enough by itself to solve any real problems. If we want sharks around (and believe me, even though the odd swimmer may get a nip or two, it’s better than the alternative of no sharks), then we’re going to have to restrict fishing effort on the high seas as well.

I think this one qualifies for the ‘Potential‘ list.

CJA Bradshaw

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