If a lobster gets in the trap first does it chase crabs out?

I did my master's thesis on behavioral interactions between lobsters and crabs (Jonah and sand crabs, Cancer borealis and Cancer irroratus) and how they affect trapping of these species. What I found was that if a lobster got into a trap first, crabs would not enter the 'parlor' or holding section. This was because if a crab started up the entry to the parlor, the lobster made aggressive displays which made the crab back down. Crabs did not keep other crabs out, nor lobsters, so if a crab got in first, lobsters would still come in. In general, these two species of crabs are less aggressive than lobsters.

What are the small crabs found inside oysters?
Are they harmful to oysters?
May humans eat them?

These are "pea" crabs. They live, often in pairs, inside the oyster shell, eating food collected on mucous strands in the oyster. Because they do cause damage to oyster mantle and gills, the crabs are considered parasites. Pea crabs are not harmful to man.

How do prawns, crayfish, and shrimp differ?

As so often happens, common names are used loosely and inconsistently in the shrimp family. The "prawn" of Great Britain and other countries is essentially the same animal as the shrimp of the United States, the only biological difference being that prawns have their second abdominal flap (counting from the head towards the tail) overlapping the first and the third. In this country, the term "shrimp" applies to all crustaceans of the Natantia group, regardless of size. "Crayfish" or "crawfish" are names given to both a common freshwater crustacean and to the saltwater spiny lobster.

Is there more than one kind of shrimp?

Numerous varieties exist, among them brown, white, pink, royal red, brine, and rock shrimp.

How big do shrimp grow?

Depending on the species, size ranges from about 1/2 inch long on the west coast of the United States, to almost 12 inches elsewhere.

How long do shrimp live?

The life cycle varies geographically and by species. Some live as long as 6-1/2 years, others live only a year.