Invertebrate investigations dominated discussions in our house last week.

For those of you that have anglers in your circles, sea lice have been the talk of the town. Last week, a striped bass with sea lice was caught, so it is ready, set, go for Island fisherfolk.

Science is selective and, in this case, it is not just a sudden interest in these small spineless species. Sea lice tell a story, one of time and travel and is a sign for locals that are angling for the return of a favorite fish.

Sea lice, sometimes called fish lice, are a large group of small crustaceans that live off the bodies of other species. This habit makes them ectoparasites, feeding off of the mucus, epidural tissue, gills and blood of their host fish. There are hundreds of species in many genera. Even on one species — striped bass — there is lice diversity. A study in the Chesapeake Bay identified more than 45 species of parasites identified on Bay striped bass.

A migratory fish, striped bass mostly going south for the winter. However, a select few will stay year-round, over-wintering in local ponds. The angler in my life calls these fish landlocked because they got stuck in the ponds when the breaches closed. And these pond-dwelling fish don’t have sea lice.

Migratory striped bass, however, that have come up from the south for their annual spring voyage north, often have sea lice on their bodies when they arrive in local waters. It is said that they get these hitchhikers in deeper waters on their seasonal journey. The presence of sea lice is the telltale sign that a fish is a migrator and not a pond holdover.

An occurrence in both wild and farmed fish, sea lice can often be specific to species. Their presence on salmon and other farmed fish is a problem and has been well researched. Fish with sea lice are a concern for that industry because of consumer distress. Our local wild stocks of bass usually have reduced appearances of lice as the season progresses with lice most often seen in the spring, but not summer and fall as the water warms.

This is a large group of little animals and are notoriously difficult to identify. One marine biologist noted that these parasites can pose quite a challenge to get them down to species level. Online photos and descriptions of sea lice include many very different photos of many different creatures from scientific orders including isopods, amphipods, and copepods. A few noted to live on striped bass include gill lice (ergasilus) and fish lice from the argulus and lironeca species.

Add to the confusion is that the term sea lice is also used to describe a rash or skin irritation experienced by beachgoers but caused by jellyfish and other larvae. More accurately, that problem is known as sea bather’s eruption and is not what our local anglers describe.

The good news is that the striped bass have arrived and even better is that these creatures won’t get you scratching and ruin a day at the beach. The only itch that might come is the one to get out and go fishing.

Suzan Bellincampi is Islands director for Felix Neck Wildlife Sanctuary in Edgartown and the Nantucket Wildlife Sanctuaries. She is also the author of Martha’s Vineyard: A Field Guide to Island Nature and The Nature of Martha’s Vineyard.