[CT Birds] Fwd: Gull / Plankton Feeding
donnacap at aol.com
Thu Mar 1 11:42:12 EST 2012
Dennis - thank you for sharing the all that information! I find this event so interesting and wanting to know more so I've been reading what I can find about it. Unfortunately there doesn't seem to be a lot of information that pertains to Long Island Sound specifically regarding this subject or on CT's Slipper Shells.
To me there seems to be several events happening at this time. It is "spring" after all and flowers and wildlife a like are "blooming" around us everyday. Far from being even a novice in birding or marine biology, what I read leads to more questions and some observations. In addition to the Barnacles and other plankton that may be blooming now, I am inclined to think the Slipper Shells are also involved. There doesn't seem to be much info on the CT Slippers breeding cycle. But articles I've been reading say they spawn anywhere from March to August (or June to September) in coastal waters. They are found in large numbers in Europe (thanks to US Oyster exports), Chile and along the eastern coast of North American. The Sound is not like a lot of coastal waters, it's more "protected coastal waters". There are concentrated large populations of Slipper Shells along LIS's coasts (Long Beach for one). According to wunderground.com the coastal waters in CT and surrounding areas the past month have been above 40F hitting 46F several times and even higher in other locations http://www.wunderground.com/MAR/AN/330.html. Slipper shells will readily spawn within a short time after being in water 25c/39F. If its not Stratford area Slippers, then perhaps larvae from surrounding areas within LIS are travelling in the currents with the Gulls following along. As the water continues to gradually warm up, various other larvae are added bringing more and more gulls. It is interesting to note that Slipper larvae will float around for up to 4 to 5 days before they attach themselves to a hard surface such as rocks (like the barnacle does) and begin the process of "growing" their shells. The photos from Keith clearly show the Gulls feasting on juvenile Slipper Shell larvae. It seems the Gulls are feasting on a buffet of barnacles and Slipper Shells and ??
I think this phenomenon as it pertains to Long Island Sound would be worthy of being studied more fully. How does it coincide with the migratory shore birds passing through or leaving our area? Did a milder winter cause an earlier spawn of all or some the different plankton? Etc., etc??
"The normal breeding period for C. fornicata in Woods Hole, MA is reported to be mid-June through mid-August (Costello and Henley, 1973), however; it is likely that animals begin spawning in May, and a few animals continue to lay eggs in August. This seasonal limitation is removed by the fact that one can obtain animals from the wild between November and May that will readily spawn within days to a few weeks of being placed in warm (25 °C roughly 39 F) sea water. Animals can be kept in chilled sea water tanks at 12°C for up to a month, without feeding, and subsequently warmed to 25 C when embryos are needed. It is imperative that these “off-season” animals be collected from the cold and shipped with ice packs to prevent them from spawning during transport." http://www.life.illinois.edu/henry/crepidula_methods.html
Interesting article re Nantucket Slipper Shells. BTW - they are edible (see article). And, they have used them to determine the age of Horseshoe crabs.
List of some articles I need to go through
Thanks for letting me share my "ramblings" on this subject. Please feel free to send my your comments privately so we don't clog up the list here. Slipper Shells are quite interesting. And when out walking Long Beach I will now have a new interest in them.
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