Cancer irroratusFOUND by chotaling
Quality checked by sleepy crab
Peer reviewed by
Our question was altered from the original question. The original question was: Are there more native species or invasive species in Casco Bay? We altered that to a more empirical question which was: Are there more native species than invasive species, as caught by a trap, at the mouth of the Portland Harbor. Very little wind. Beautiful sunny day with Captain Tom on the Lucky Catch. Group of three researchers. Happy to be on the water. We hauled four traps, and our group focused on #3, which was in 35 feet of water with sandy bottom habitat. Just off Porland Head light. On the way to our site, we noticed Herring Gulls, Greater Black Backed Gulls, Cormorants, and one Harbor Seal. Our boat hauled traps 1 and 2 at a location farther in the harbor. They found many more lobsters and we attracted many more gulls than at our hauling location. Native species found in our trap were: 2 sand snails (maybe oyster drillers) 2 other snails (very small, like periwinkles) 1 nudibranch polysiphonia irish moss cladophora or maybe chaetmorpha 12 rock crabs (two with eggs and 11 were female) fucus hydroid 1 anthropod We predicted that we would find fewer invasive species than native species (counting types of species, not total abundance). Our prediction was based on our thoughts that Casco Bay is relatively pristine. Perhaps more importantly, we reasoned that we were not so near the shore, where, in our past experiences, more invasives are found. We were pleased to find this habitat is not significantly threatened with competition for local resources by invasives, based on this limited sample area and specific trapping technique. We did not find any invasive species at Trap #3. However, the trap next door to ours hauled at the same site found two invasive species. The limited sample and invasives found by trap 4 but not recorded by us compels us to take more data in order to support or refute our conclusion. This was a deep water, sandy habitat. Our Captain shared, afterward, that he tends to find more of one invasive species, green crab, close to shore.
The shape of the carapace provides us evidence that this a rock crab, and not a Jonah crab. It flares up from the abdomen in straight lines to the spikes at the sides of the carapace. Jonah crabs are similar, but have a more oblong carapace.
This crab has 8 spikes, which would identify it as a rock crab or jonah. But because of the evidence about the carapace shape provided above in evidence #1, we conclude that this crab is a rock crab.
N 43.624190 °
W -70.207290 °
Portland Head Light
Tue, 2012-08-14 10:53
Town or city:
Type of investigation:
Fore River, Portland Harbor (Casco Bay)
Time of low tide:
Tue, 2012-08-14 10:56