Caplin have rolled on Newfoundland and Labrador beaches for centuries.

However, the collapse of the caplin stock off the North Coast of Labrador in the 1990s and its sudden resurgence in 2013 have sparked a debate on the true origins of the fish.

Previous studies have shown that caplin in Newfoundland and Labrador share common ancestry and come from the northwest area of the Atlantic Ocean. However, other researchers have produced a hypothesis that the Labrador Sea represents a mixing zone for caplin belonging to Arctic, Northeast-Central Atlantic and Northwest Atlantic populations. It is therefore probable that caplin on the North Coast of Labrador did not undertake a southward migration during the 1990s, as previously assumed, but migrated northward instead.

Today, the genetic structure of caplin populations still remains largely unknown. Dr. Marie Clément of the Marine Institute’s Centre for Fisheries Ecosystems Research and based at the Labrador Institute in Happy Valley-Goose Bay has assembled a team of researchers to determine whether caplin now returning to the North Coast of Labrador belong to northern or southern populations.

“For managing this important forage species, I believe that it is important to track the origins of the caplin returning to coastal Labrador and to compare life history traits with other caplin stocks,” Dr. Clément said.

During the initial phase of the project, which began in July 2015, fin tissue samples were obtained for genetic analysis and whole fish were preserved for future caplin body measurements and age determination at 18 sites in Labrador, Quebec’s Lower North Shore, Nunavut and Greenland.

Local knowledge

“Caplin spawning season is very brief and the locations of spawning are highly variable,” Dr. Clément said. “Therefore, this project relied principally on local samplers with knowledge of spawning locations at each sampling site. The project’s success largely depends upon collaboration with Nunatsiavut and NunatuKavut conservation officers, local fishers, commercial harvesters, the Labrador Fishermen’s Union Shrimp Company, provincial and federal governments, the Greenland Institute of Natural Resources and academics working in different regions.”

Should it be true that the caplin migrating back to Labrador belong to Arctic populations, Dr. Clément believes the stock management plan currently used in Newfoundland and Labrador waters will need to be revisited.

“Changes in caplin population dynamics have had severe consequences on the productivity of Newfoundland and Labrador marine ecosystems,” Dr. Clément said. “For example, Atlantic cod, an important caplin predator, experienced a simultaneous collapse in the early 1990s and has since remained at low levels in the absence of their main prey, among other factors.”

Caplin is also an important forage or prey species for many other fish, mammal and bird species and is therefore considered a keystone species in marine ecosystems. A better understanding of caplin populations’ genetic structure and life history traits is therefore necessary for fisheries management.

Based on the tremendous success of the work done in the 2015 field season, Dr. Clément will further develop the project with her collaborators to generate the information needed to better understand the caplin of Labrador.