Abstract
More than 5 million Canadians take part in recreational angling each year, spending over 50 million days fishing on open water. Recreational anglers
contribute to environmental lead deposition through the loss of lead fishing sinkers and jigs. Each year, lost or discarded fishing sinkers and jigs amounting to an estimated 500 tonnes of lead, and representing up to 14% of all nonrecoverable lead releases in Canada, are deposited in the Canadian environment. Wildlife, primarily piscivorous birds and other waterbirds, ingest fishing sinkers and jigs during feeding, when they either mistake the sinkers and jigs for food items or grit or consume lost bait fish with the line and weight still attached. Lead fishing weights that weigh less than 50 g and are smaller than 2 cm in any dimension are generally the size found to be ingested by wildlife. Ingestion of a single lead sinker or lead-headed jig, representing up to several grams of lead, is sufficient to expose a loon or other bird to a lethal dose of lead. Lead sinker and jig ingestion has been documented in 10 different wildlife species in Canada. In the United States, ingestion of lead sinkers and jigs by 23 species of wildlife, including loons, swans, other waterfowl, cranes, pelicans, and cormorants, has been documented. Evidence gathered to date indicates that lead sinker and jig ingestion is the only significant source of elevated lead exposure and lead toxicity for Common Loons Gavia immer and the single most important cause of death reported for adult Common Loons in eastern Canada and the United States, frequently exceeding deaths associated with entanglement in fishing gear, trauma, disease, and other causes of mortality.
Except for a few local or regional instances, available data indicate that Common Loon populations are stable or increasing through most of their Canadian range. There is currently insufficient information to answer the question of whether mortality through lead sinker poisoning may be having population-level effects on loons anywhere in Canada or to estimate with confidence the minimum frequency of poisoning that, combined with the effects of other environmental stressors, would be required to significantly affect population dynamics. The most critical areas of new knowledge that are required to enable confident estimates of the population effects of lead sinker poisoning in loons are accurate life history data using individually marked birds to derive important population parameters for local or regional loon populations in Canada; DNA analyses to better define "populations"; a better understanding of the interactions of multiple environmental stressors that may influence population dynamics; and incorporation of these multiple stressors into a large-scale spatial analysis using geographic information systems. Such research would be expensive and time-consuming, requiring long-term monitoring of substantial numbers of banded individuals from several selected populations.
There are numerous viable alternative materials for producing fishing sinkers and jigs, including tin, steel, bismuth, tungsten, rubber, ceramic, and clay. Tin, steel, and bismuth sinkers and bismuth jigs are the most common commercially available alternatives in Canada. Many of the available alternative products are currently more expensive than lead; however, switching to these products is anticipated to increase the average angler's total yearly expenses by less than 1% (~$2.00). Nevertheless, the continued availability of (cheaper) lead products has made it difficult for the manufacture and sale of nontoxic alternatives to achieve commercial viability.
Some limited regulatory actions have been taken to reduce the use of lead sinkers and jigs both in Canada and elsewhere. In 1987, Britain banned the use of lead fishing sinkers weighing less than 28.35 g. The United States has banned the use of lead sinkers and jigs in three National Wildlife Refuges and in Yellowstone National Park and is currently considering further action. New Hampshire, Maine, and New York have ratified statewide regulations prohibiting the use of lead sinkers beginning in 2000, 2002, and 2004, respectively. Environment Canada and Parks Canada prohibited the possession of lead fishing sinkers or lead jigs weighing less than 50 g by anglers fishing in National Wildlife Areas and National Parks under the Canada Wildlife Act and the National Parks Act, respectively, in 1997. However, these latter two regulations are of limited geographic scope, covering <3% of Canada's land mass, and they affect only about 50 000 (<1%) of the estimated 5.5 million recreational anglers in Canada. Currently, the majority of recreational anglers continue to use lead sinkers and jigs.
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