SEAFOODNEWS.COM (SeafoodNews) — June 3, 2015 — For the past five years, the Province of Newfoundland and the Marine Institute have been funding special cod surveys using the Celtic Explorer, a research vessel from Ireland.
These surveys have documented the increasing populations of cod in the tradtional spawning areas in the Bonavista Corridor, where the remant population after the 1992 collapse was concentrated. According to Dr. George Rose, the rebuilding of the Northern Cod stock “parallels the North Sea cod story but of course the northern cod has much larger potential for stock growth.”
In the words of Dr. Sherrylynn Rowe, CFER Research Scientist, who is aboard the Celtic Explorer on this current trip, “During most of the post-moratorium period, the small amount of cod that remained offshore was concentrated in an area known as the Bonavista Corridor spanning the NAFO 3KL boundary. Our time series of acoustic-based abundance estimates in the Bonavista Corridor extends back to 1990. Over the last several years, we have observed extraordinary changes in cod within this area with much evidence that the stock is on the cusp of a major rebuild of world-wide importance to fisheries science and management. ”
This bodes well for the years to come, says Dr. Rowe. “The increasing numbers of large ‘mother fish’ should contribute disproportionately to egg production and recruitment of young fish. Indeed, the fall DFO research vessel trawl survey suggests that recent year classes of cod may be strong and widespread, including in northern portions of the stock area which were barren for many years. The possibility that these young fish might survive to grow and spawn as adults provides reason to be optimistic about the future of this once great fish stock.”
However, Dr. George Rose who is regarded as the foremost expert on Northern Cod, has suggested that cod spawning off southern Labrador was the engine that drove the great northern cod stock of former centuries and he predicted that substantial recovery would not occur until this area repopulated.
According to Dr. Rowe, “Two decades after the collapse of the early 1990s, we are seeing this happen.”
The clue was presence of young cod off Labrador which “intrigued myself and Dr. Rose prior to the trip.”
Dr. Rowe: Cod are broadcast spawners with floating eggs and larvae that drift for several weeks during development before settling to the sea floor. The southward-flowing Labrador Current makes it unlikely that juveniles in the north resulted from spawning in the Bonavista Corridor – the only known area of offshore spawning since the moratorium.
We surmised that major spawning must once again be underway off Labrador, as it was during the hay day of the northern cod.
During 2013 and 2014, our survey of cod off Labrador was hampered by severe ice conditions, particularly in 2014 when we could not go much beyond 50°N. The Celtic Explorer is not suitable for working in ice. This year, we were able to access waters as far north as Hamilton Bank and obtain our best survey coverage to date.
“Our efforts were rewarded. Over the course of our 2015 survey, we identified and measured two new spawning locations well north of the Bonavista Corridor. These aggregations contained numbers of large fish not recorded in these areas for decades. They are almost certainly the source of the young fish now evident in the north and the larger fish reported by harvesters to be abundant along the northeast Newfoundland coast and off Labrador in recent fishing seasons. ”
“Thanks to funding provided to Dr. Rose and myself by the Government of Newfoundland and Labrador, we have been able to deploy the latest generation of pop-up archival satellite tags to study cod movements and behaviour. Much of this work up until now has been focused in the Bonavista Corridor but this year, we were able to successfully tag fish from these more northerly aggregations. The resultant information is providing brand new insight to the distribution and movement patterns of fish from these various areas.
Amazingly for all the centuries of the cod fishery off Newfoundland, little was known about spawning aggregations. Dr. Rose using acoustic surveys has identified highly visible spawning columns of cod that rise over 100 meters off the sea floor. These columns were clearly seen in the new spawning areas, and some sampling was done of individuals from the tops of these columns.
Dr. Rowe says that while the precise numbers remain to be determined, identification of these new spawning aggregations will undoubtedly increase substantially our estimates to date. Over the coming months, myself and Dr. Rose will be analyzing the myriad of data collected on this voyage to estimate biomass and abundance of the spawning stock.
More details on the survey can be found at the cruise’s online blog, Scientists at Sea.
Photos: New Cod spawning aggregations from Celtic Explorer; Dr. George Rose on the Gecho II acoustic research vessel.
This story originally appeared on SeafoodNews.com, a subscription site. It has been reprinted with permission.