Shrimp test fisheries guide harvest management

Suquamish shellfish staff haul in spot shrimp to sample.

The Suquamish Tribe conducted its annual fishery to test spot shrimp egg production in March, concurrent with other tribes and the state running their own shrimp test fisheries.

The test fishery determines whether the shrimp population is ready for harvest by counting females that have dropped their eggs. If the percentage of females without eggs is 3% or fewer, then the fishery is ready to open for that particular catch area without damaging the population, said Viviane Barry, the Suquamish Tribe’s shellfish program manager. Typically fisheries managers strive for opening in April or May, depending on the region.

“It can vary from year to year, depending on environmental conditions and water temperature, but typically at this time of year in Marine Area 10 (Central Puget Sound), shrimp have dropped their eggs by now,” Barry said.

The test fishery targets females but also captures males and transitional shrimp. Shrimp are born protandric hermaphrodites, which means they are born male and transition into female later in life. This strategy is a way for the species to maximize the lifetime reproductive output of individual shrimp, Barry said.

During the pre-season test fishery, in addition to looking for eggs, scientists inspect every shrimp to see if it is male, transitioning or female by looking for the presence of a tiny copulatory appendage next to the second pleopod, or swimming leg, near the abdomen.

For Marine Area 10, the fishery opened May 3 but performance was low, Barry said, as shrimp beds were patchy; some fishermen did OK while others did not land any shrimp.

After the season, the state and the tribes may conduct a post-harvest test fishery in September to determine whether a population was overfished or underfished. The data can help managers assess the female abundance in the population at the beginning and end of the fishery, Barry said.

In general, across Puget Sound, shrimp abundance increases from south to north, as do sizes. One exception is the Hood Canal where shrimp are more abundant than in the Central Sound main channel, she said.

“Crustaceans, such as shrimp and crab, are generally more abundant in north Puget Sound where there’s more true, cold marine waters,” Barry said. “Spot shrimp like really deep and cold water with habitat complexity that provides shelter from predation.”

A spot shrimp is measured for length during an egg test fishery conducted by the Suquamish Tribe. Story and photos: Tiffany Royal