Overfishing is often seen as the single biggest threat to marine life, as more and more people are competing for fewer fish. Over the last decades shark catches in many parts of the world have steadily increased as a result of an overall intensification of marine fisheries and increasing human populations, but also due to the growing demand for shark fins.
Commercial fishing is the greatest threat to shark species. Sharks may be directly targeted or taken unintentionally as 'bycatch' in other fisheries. Worldwide, a number of shark species continue to be directly targeted by fishing practices. In addition, many challenges face marine managers and conservationists in mitigating shark population decline, because of their inherent biological characteristics of slow growth, late maturity, long life and low fecundity. These fisheries often follow a "boom and bust" pattern, with sudden collapses of population and a reduction or closure of the fishery (e.g. porbeagle fishery in Atlantic Canada). The nature of these types of fisheries has raised doubts as to whether or not shark fisheries can ever be sustainable.
In Canada, few shark species are subject to a directed fishery. The spiny dogfish, exploited on the Atlantic and Pacific coasts, is the most important commercial shark species in Canada. With the exception of the Canadian portion of Georges Bank, both coastal populations appear to be stable.
To a lesser extent, large pelagic sharks have been exploited in Atlantic Canada since the 1960s. The porbeagle shark is the only large shark for which a small directed fishery is currently active. This particular fishery has had a chaotic history; however, despite this, it is among the best studied, controlled and monitored of all shark fisheries. A directed blue shark fishery is also permitted in Atlantic Canada; however, it is not active due to these sharks’ low market value. In recent years, nearly all landings of blue shark consisted of bycatch from the commercial fishery. The shortfin mako shark does not have a directed fishery. Instead, this shark may be retained and landed as a bycatch species in some fisheries.
Canada is not a major game fishing nation; nonetheless, two forms of recreational shark fishing exist in Atlantic Canada: catch and release and shark derbies. The catch and release fishery is designed to return all sharks to the water alive; however, there is inevitably some level of hooking mortality. Derby tournaments in the Atlantic Maritime region have grown in popularity in recent years. Popular targets for anglers are shortfin mako, porbeagles and thresher sharks because of their fighting ability; however, the most commonly caught species is by far the blue shark. In Canadian waters, shark derbies have only been estimated to account for about 3% of the total fishing mortality of blue sharks. In recreational shark fishing, both catch and release and derby participants are required by the license condition to complete and submit scientific data logs on catch-by-catch basis to DFO; however, less than 2% of the recreational licenses (excluding derbies) return fishing logs.