The Maritimes Recreational Shark Fishery has been active since 1994. Biological data collected from the recreational fishery is used to develop an assessment of stock status and the general health of the population, particularly that of blue sharks. For the purpose of scientific data collection, participants of the recreational shark fishery are required to provide information on length, weight, sex and location of every shark that is caught, whether or not it is landed or released. By monitoring trends in this data from year to year, and in conjunction with the more detailed information collected at the shark derbies, the scientists at the Shark Research Laboratory are able to detect population-level changes which are indicators of low stock abundance or overfishing. Biological indicators such as the size composition, size at sexual maturity and catch per fishing effort are particularly useful for detecting problems with the population. While there are social and economic benefits to a healthy shark fishery, the fishery must be sustainable over the long term. In other words, the populations of each of the shark species must be conserved at safe levels.
Click on the fingernail photos to view the full size image
Shark fishing derbies are held each year in waters off Nova Scotia, usually during the months of July, August and September. These are commercial or community-sponsored events, and are not sponsored by DFO or the Shark Research Lab. However, the catches provide excellent samples for scientific examination, and thus all catches are closely monitored. The species most often caught is the blue shark. However the occasional thresher or porbeagle shark is also caught. Shortfin mako sharks, like the one in the photo below, are not uncommon in Canadian waters, although this particular specimen is unusually large. Other species of shark do occur in Nova Scotian waters. However many of them prefer warmer waters that are associated with the Gulf Stream, or deeper waters which make them unlikely to be caught by recreational anglers.
The number of shark derbies and participants has been increasing ever since their inception, and biological data has been collected at each of them every year. Most of the sharks caught during the derbies are landed rather than released. It is from these animals that lengths, weights, sexual maturity and stomach contents can be recorded and analyzed. Vertebrae are sometimes collected for age determination. The data collected up until 2004 has now been analyzed and a first report on the impact of shark derbies on the health of the blue shark population has been published. The report Influence of Recreational and Commercial Fishing on the Blue Shark (Prionace Glauca) Population in Atlantic Canadian Waters found that blue sharks caught at shark derbies accounted for only 3% of the blue sharks killed annually in Canadian waters, and thus were having a negligible effect on the population. Accidental bycatch from commercial fisheries was the major source of fishing mortality on blue sharks, and was probably responsible for a recent modest decline in population numbers. Almost all of this mortality comes from foreign boats fishing outside of Canadian waters. Nevertheless, the Shark Research Laboratory will continue to monitor the population closely.
Beginning in the summer of 2006, the rules for all
derbies were changed. Under the new rules, all blue sharks less than 240
cm (8 feet) are to be released alive, preferably after tagging. Tagging is
voluntary, but is strongly encouraged by DFO Science, and a tagging kit is
provided to all fishing captains before the start of the derby. Along with
tag number, derby participants report information such as length, sex, location and water
temperature on their tagging forms, which are turned in to DFO biologists at the
end of each derby fishing day. Sharks larger
than 240 cm (8 feet) can continue to be landed, as can sharks of any size other than blue sharks.
Live release of porbeagle sharks, which have been listed as endangered by
COSEWIC, is also encouraged. The large numbers of sharks
tagged by derby participants will be of great scientific value to DFO Science,
since the recapture rates will be used to provide better estimates of blue shark
mortality rates. Click here for
information on tag recaptures.
The number of sharks caught per year at each derby can be found in the table below. Note that the rules for landing sharks at derbies were changed in 2006, which resulted in fewer sharks being landed.
The total weight landed per year at the blue shark derbies can be found in the table below. Note that the rules for landing sharks at derbies were changed in 2006, which resulted in fewer sharks being landed.
Weights landed per year
Some interesting shark derby statistics are presented below: