Fishermen and Scientists Research Society (FSRS) and Fisheries and Oceans Canada (DFO) Collaboration
Understanding where and how many Stage-IV (settler or young-of-year) lobsters settle on the ocean bottom has been a challenge for scientists. Suction sampling with divers is one approach but this generally restricts sampling sites to depths less than about 20 m, and suitable diving conditions. Another approach to sampling lobster settlers is to deploy passive collectors--- wire mesh cages filled with cobble sized rocks. These can be deployed in a wide depth range and do not require divers. Collectors can be used to provide estimations of annual abundance of lobster settlers and juveniles throughout Nova Scotia.
In 2006, a collaborative project between the Fisheries and Oceans Canada (DFO) and the Fishermen and Scientists Research Society (FSRS) was formed to better understand the settlement of Stage-IV American lobsters in deep and shallow areas at selected regions along the coast of Nova Scotia. Settlement collectors using a design from Richard Wahle and co-workers in the United States were first deployed in Lobster Bay (Argyle) in 2007.
When lobster larvae hatch out of eggs during mid- to late summer, they are “planktonic”---floating in the water column with limited swimming ability. This period lasts 3 to 6 weeks depending on water temperature. During this planktonic period, the lobster larvae will moult through three larval stages and undergo metamorphosis to a post-larval stage (a Stage-IV lobster or “young-of-year”). A Stage-IV American lobster resembles a miniature lobster and has a carapace length measuring ≤13mm. At this stage (Stage-IV), they begin to search for shelter in a suitable habitat on the ocean bottom. To mimic the preferred habitat of Stage-IV lobsters settling to the bottom, passive collectors filled with cobble to provide shelter were deployed on select ocean bottom types.
Collectors are deployed in select regions along the coast of Nova Scotia in late June and July (Table 1) and left undisturbed on the ocean bottom. They are deployed in water depths ranging from 3 metres to 47 metres. In October and early November, collectors are retrieved using the surface buoys (a few areas) or by dragging a grapple for collectors with no surface buoys (most areas).
Length frequencies are taken for all lobsters, crabs and fish, along with the collection of biodiversity samples at each region. In addition to finding young-of-year lobsters in the collectors, juvenile lobsters are also found (carapace length up to 60mm). Temperatures are also recorded at each site within a region using a VEMCO minilog.
The years that each location participated in the lobster settlement collector project
2008 - 2013
Big Bras d’Or
2009 - Present
Saint Mary’s Bay
2009 - Present
2008 - Present
*Sampling in the Canso-Whitehead area is completed by Guysborough County Inshore Fishermen’s Association (GCIFA) and DFO.
Scientists Adam Cook (Fisheries and Oceans Canada), Rick Wahle (Bigelow Laboratory for Ocean Sciences, Maine) and Rémy Rochette (University of New Brunswick), along with their colleagues are collaborating to better understand the dynamics of settlement of American lobster and to develop an index on annual settlement that will be useful for predicting future recruitment into the lobster fishery. The work in Canada complements an index of lobster settlement in the US that has been measured in several locations for more than 20 years.
The Lobster Settlement Collector Project takes much time and hard work. It would not be successful without the participation and tenacity of fishermen, along with the efforts of FSRS and DFO personnel. The advice and skills on the water provided by fishermen are greatly appreciated.
This project requires not only people but funding. Thanks to the Nova Scotia Department of Fisheries and Aquaculture for providing funding to FSRS to support the project and to Fisheries and Oceans Canada for special funds to support the participation of DFO Science.