Dear Team,
The cold weather has been borderline unsuitable for horseshoe crab breeding, yet the crabs persist. The bay water temperature briefly topped the 59-degree threshold temperature for crab spawning at the Cape May Buoy last night for a few hours, then fell to an unsuitable 57 by dawn. The crabs spawned in good numbers but not in all places. For example, Reed’s Beach had a good spawn, but Fortescue did not. As I finish this update, it looks like the bay temperature probably won’t get back to 59 degrees in time for tonight’s full moon high tide.
The water temperature in Delaware Bay remains too cold for peak horseshoe crab spawning. The water temperature must rise above and stay above e 59 degrees
Shorebird numbers remain low. We counted 2 thousand red knots yesterday, low for this time, when in 2019 we had about 7,000. The southerly winds of the last few nights should bring in more birds. Ruddy turnstone numbers are similar to red knot but spread more widely in along the Delaware Bayshore. David Mizrahi reports that semi-palmated sandpipers are still low in numbers compared to previous years.
We’ve made three catches this week. We caught 67 ruddy turnstones and a handful of red knots on Saturday the 14th, 45 red knots on the 15th, and another catch of 65 red knots yesterday. Stephanie Feigin also attached nine satellite transmitters yesterday, including three Lotek Sunbird tags, a brand new device powered by a small solar panel mounted on the back of the transmitters. She also attached Lotek Pinpoint Sat Tags which can send back 60 bird locations that can be programmed to last for a year. The new Sunbird tags will provide unlimited locations if the tag is charged. The average weights for the knots are normal for this time of the month.
A red knot with a new Lotek Sunbird Solar powered satellite transmitter
Today we finished our experimental crab spawning areas to define better the relationship between buried horseshoe crab eggs and those on the surface. I am almost embarrassed to report that otherwise, respectable fishery biologists challenge the connection. They say the relationship is weak and use this lack of correspondence to justify ignoring all these vital data showing horseshoe crabs have yet to recover from their ill-advised harvests.
We constructed three fenced areas to concentrate horseshoe crabs into denser numbers to simulate the densities seen before the overharvesting of crabs in the 1990s. Two parallel fences run down the intertidal zone and at the low tide line spread to encompass three times the area in a sort of horseshoe crab funnel. Crabs crawl towards the beach hit the funnel, and hopefully crowd into the intertidal beach. We will conduct egg surveys identical to all beach surveys and compare the relationship between surface and buried eggs.
Fences that will concentrate horseshoe crabs into a smaller spawning area, simulating a higher density of crabs. photo by S. Feigin
Contrary to the fisheries biologists, the relationship between buried and shallow eggs is quite strong. Eggs mostly reach the surface at low crab densities because of wave action, so this is the cause of the lack of correlation between buried and shallow egg densities. But as the density of crabs increases, more females dig up the eggs of previously laid egg masses, and the correlations grow stronger. At equilibrium, every female laying eggs digs up an equal number of eggs, and the relationship is near perfect.
In other words, fishery biologists fail to recognize that they cause the poor correlation between buried and surface eggs because they refuse to restore the crab population. We hope to describe the relationship better to address this controversy with sound science.
We have been blessed once again this year with the volunteer cooks organized by Jane Galeto and Citizens United. Doreen Horman, CU’s events coordinator, made us dinner the night before a scheduled hospital visit. The firefighters from Mauricetown, NJ, made us a big pot of delicious oyster stew, using a recipe they never divulge. The cooks inspire us while filling our stomachs.
