Herring larvae is the focus of an ichthyoplankton sampling project initiated last year by the industry-driven Herring Science Council and is already producing “interesting” results which will hopefully lead to a better understanding of the stocks in southwestern Nova Scotia and the Bay of Fundy.
In an interview, program coordinator for the Council, Jenna Munden, said the first survey season was very successful.
“We caught over 500 herring larvae last year,” she said. “It was really interesting. We were able to measure the larvae and calculate when those larvae would have been spawned on the spawning grounds and were able to determine they were likely spawning earlier in the year than when we were doing our surveys so this year we went up to Scot’s Bay earlier than we ever did based on our larval samples and indeed there was spawning so that was a really interesting result. It has allowed us to figure out more information about herring spawning.”
Munden said the first survey, conducted on June 9, was two weeks earlier than last year.
“We did see a good sign on our first survey which was nice,” she said. “The fish haven’t been documented at that time of year before so we’re not sure if this is something new or just something we didn’t know.”
Surface tows are conducted in conjunction with acoustic surveys to obtain the larval samples from the spawning grounds. An analysis of the larvae is done to get an idea of when they spawned how many spawning waves have potentially occurred.
The Herring Science Council also conducts a tagging program, which “is just ramping up,” said Munden. “We wait until we have enough consistent fish to go and tag the pre-spawning population.” This is the third year of the tagging project. Each year 20,000 tags are inserted into healthy pre-spawn herring in the Bay of Fundy and southwestern Nova Scotia during normal fishing operations.
The movement patterns of pre-spawn fish from feeding to spawning grounds in the main research question. After the fishing season ends for the year, a draw takes place with the names of individuals who submitted tag returns, with prizes for the first ($1,000), second ($500) and third ($250) awarded.
Acoustic surveys are the main science aim of the Herring Science Council and have been conducted by the purse seine fleet in southwestern Nova Scotia since 1999. The single-beam, hydro-acoustic surveys are conducted by the nine-vessel fleet every two weeks from June until October, monitoring Scots Bay and German Bank spawning grounds. On average, a dozen surveys are completed each year. The acoustic data provides an initial biomass estimate of each spawning component to DFO.