No. 22–Questions and Answers
A recent visitor to the Estuarium posed an interesting question I hadn’t considered before. I had just finished explaining to a group how local terrapins went to fresh water to drink to balance the salts in their system because of the high salinity of the estuary. The person asked if river otters fulfilled their hydration needs through the food they ate or if they had to drink water in addition. Not being certain of the answer I told the person (a local resident) that I would find out and they could monitor this column for the answer. My colleague Chris Marsh with the Low Country Institute provided the answer below.
A. The answer is probably “yes” – even marine fish have low salinity, and since they eat frogs and other fresh water species, they probably get their water this way. They are able to expel salt from their blood through their kidneys like humans do, but have to be visiting fresh water regularly also.
Q. I understand we have the highest tides on the spring tides but why are they higher some months than others?
A. Just as important as planetary alignment during the new and full moon cycles is the relative distance between earth, sun and moon in their orbits. The gravitational forces of the two bodies increase and decrease relative to their proximity to earth.
Q. Why do crabs always run sideways?
A. It’s true that crabs have no problem moving forward and back slowly, but think about it. They have eight legs – four on each side. They would trip all over themselves if they tried to run forward.
Q. What are the almost see-through little shrimp I get when I throw my cast net near shore?
A. They are one of several species of grass shrimp. Also known as shore shrimp, large concentrations may occasionally be seen moving in-mass along the shore. The prickly-tickly sensation one experiences when wading bare legged in the river or a creek is the result of the shrimp using their tiny pincers to feed on dead epidermal cells. Salt marsh exfoliation if you will.
Q. I sometimes get some nice size mullet when shrimp casting, are they any good to eat?
A. You bet – if properly cared for. The fresher the better when for the eating. Do not freeze store unless it’s for bait. It’s an oily fish and it’s table quality drops sharply when frozen. I particularly like them slow smoked straight from the river.
Q. I caught a fish that had big pill bug like looking things on its gills. What were they?
A. The common name is gill louse. It is one of a myriad of parasitic isopods tormenting a wide range of species in any number of ways. Other species of isopod invade the scales and mouths of fish while still others parasitize crustaceans.
Q. We have moved into a new house by a marsh and keep finding small black crabs in our garage. They are very quick when you try to catch them. What are they?
A. The common names are square back and wharf crab and they are quite agile out of necessity. They inhabit the marsh fringe living in burrows under dead spartina and other shoreline flotsam but can range widely in search of food. Sometimes they just plain get lost. They are able to breath air for extended periods in their damp environment which puts them on the menu raccoons, mink and birds. Hence the need for speed.