Wednesday, March 18, 2009

Maryland Announces New Horseshoe Crab Policy

Some conservation groups are praising Maryland's new horseshoe crab policy. Maryland, like other mid-Atlantic states, has been trying to rebuild the populations of horseshoe crabs and the shorebirds that depend on their eggs while maintaining a profitable commercial fishing industry. Horseshoe crabs come ashore along the Atlantic coast to spawn in late spring, and many shorebird species time their migrations to arrive in our area when fresh horseshoe crab eggs are most abundant. Red Knots were hit particularly hard by the sudden spike in horseshoe crab harvests in the 1990s and remain on the brink of extinction as a result. Other shorebirds like Semipalmated Sandpipers are also threatened by the reduced food supply.

It is not clear to me that this new policy is significantly better than the default option offered by the Atlantic States Marine Fisheries Committee. The ASMFC has set a harvest quota of 170,000 crabs in Maryland for the past two years. All the Maryland policy appears to add to the commission's policy is a 2:1 male-to-female harvest ratio. So crabs will continue to be removed from beaches at the same rate as last year, but there may be more females to lay eggs.

By most accounts, it will take some time before the Red Knot population can recover. First, horseshoe crabs need to recover sufficiently to provide a large mass of eggs on Atlantic coast beaches. Since horseshoe crabs take nine years to mature and spawn, that could take a decade or more. Red Knots presumably will need even more time for their population to reach stable levels. So over all that time, there will be a continual need to have harvest restrictions in place.

If government agencies continue to push male-only harvests or 2:1 male-to-female ratios in order to sidestep the issue of whether the overall limit is low enough, then over time we may see the development of an unnatural imbalance in the numbers of male and female horseshoe crabs. For the present that may not be too much of a concern, since the sex ratio is presumably close enough to natural. In the future, it could have unintended effects if pushed too far, such as making it more difficult for females to find enough mates or reducing genetic diversity among younger crabs. It is an issue that bears watching, and I hope that our regulatory agencies have taken it into account in their planning.