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The Practical Biological Impacts of Banning Lead Sinkers for Fishing

Position of the American Sportfishing Association
December 4, 2002

Issue
Mortality in some waterfowl species has been linked to ingestion of
lead fishing sinkers and has prompted several states to impose bans on
the sale or use of lead sinkers. In response, the American Sportfishing
Association has reviewed the existing science on the effects of lead on
waterfowl populations to ensure further regulatory action is based upon
the best available information.

Background

The most publicized instance of lead poisoning (toxicosis) in
wildlife is the well-documented death of significant numbers of dabbling
ducks from ingestion of spent lead shotgun pellets expended over water.
Lead shot was shown to cause at least two million waterfowl deaths each
year, and significantly affected duck populations nationwide, before
lead shot restrictions were enacted and alternatives developed.
Deliberations on the science, economic, and social impacts of a
possible lead shot ban were thorough and involved all possible
stakeholders including industry, sportsmen, environmentalists, and
scientists. Key for the shooting sports industry was finding a
substitute that had comparable ballistics to lead and did not cause an
unacceptable crippling rate. In the end, the protracted discussion and
depth of research stemming from that issue ultimately resulted in
federal regulations that prohibited use of lead shot for waterfowl
hunting in all 50 states (enacted in 1986 for phased implementation by
1991).
As early as 1988, some loon advocacy groups expressed concern about
the death of waterfowl, especially common loons (Gavia immer), from the
ingestion of lead fishing sinkers. However, it was not until 1994 when
the Environmental Protection Agency (EPA) offered a proposed rule
banning the nationwide use of lead and zinc sinkers for fishingthat the
issue gained national attention. The final rule would have prohibited
“all persons from: 1) manufacturing, 2) processing, 3) distributing
(selling), and 4) importing any lead- or zinc-containing fishing sinker
(including brass) that is one inch or under in any dimension.” The
proposal caused immediate public opposition and was in fact responsible
for elicitingthe largest number of comments on an EPA draft rule to
date. The EPA subsequently withdrew the rule because of insufficient
data to support its supposition that lead sinkers were adversely
affecting water bird populations.
The enactment of new federal regulations banning the use of lead
shotgun pellets had set the stage for further investigations into the
effects of lead fishing tackle on wildlife, especially common loons
(Gavia immer)in New England. In 1992, a study released by Tufts
University School of Veterinary Medicine professor Mark Pokrus indicated
approximately 50 percent of loons brought to the school for necropsy had
likely died from ingestion of lead sinkers.1 This study became
thedriving force behind the effort to ban lead fishing sinkers.
Ever since the Pokrus assertion that loons are at risk from lead
sinkers, states within the summer breeding range of common loons have
experienced increasing pressure from loon advocacy groups to ban lead
sinkers, especially small split shot under ½ ounce in weight. Smaller
lead sinkers are targeted because they may approximate the size of
gravels ingested by loons to aid in their digestive process. Indeed,
citing the Pokrus study as evidence, the state of New Hampshire in 1998
(effective in 2000) became the first state to ban the use of lead
sinkers. New Hampshire was soon followed by Maine in 2001 (effective
January 1, 2002) and most recently New York in 2002 (effective May
2004). In general these states have banned the sale of lead sinkers ½
ounce or less, with the exception of New Hampshire that prohibits the
use of lead sinkers up to one ounce and lead jigs up to one inch in
length. While each state has taken a different legislative approach,
the background material furnished to legislators to substantiate the ban
has generally been the same study by Pokrus.

Different Cases: Lead Shot vs. Fishing Sinkers
Although the shotgun pellet and fishing sinker issues may appear
similar, the quality and scope of the scientific data make each case
remarkably different. In determining the impact of spent shotgun shells
on waterfowl, a nationwide effort covering several years and samples
from millions of waterfowl was conducted. Evidence from the research
was scrutinized closely by hunters and the general public and ultimately
proved, under close scientific review, that lead toxicosis from spent
shotgun pellets shot over shallow water was a significant mortality
factor affecting waterfowl populations.
Meanwhile, the most commonly cited evidence for sinker bans
remains Pokrus’ decade-old paper dealing with loon mortality from lead
fishing sinkers. Despite data for this paper being limited in sample and
geographic scope, its sweeping conclusion is that lead sinkers have the
same potential to cause lead poisoning in aquatic species as shotgun
pellets spent over water.
To fully understand the inherent difference between the two cases,
one must contrast the number of lead sinkers introduced to a body of
waterversus the number of spent shotgun pellets. One single shell shot
over water expends approximately 225 to 430 small lead pellets into the
water, depending on the load, gun gauge, and shot size chosen by the
hunter. Over the course of a waterfowl season, millions of lead pellets
may be introduced to a body of water. This in turn leads to an
increased chance of dabbling ducks, and other water birds, mistakenly
ingesting the lead pellets as they select small rocks or grit to assist
with their digestive process.
In contrast, it is not predetermined that any lead fishing sinkers
will be left in the water, although it is likely that some will be lost
over the course of a season. Fishing sinkers are reusable and unless
the line snags on an obstruction or is broken by a fish, the lead is
typically not left in the body of water. As a result, the opportunity
for ingestion of lead sinkers by water birds is greatly lessened by
virtue of there being far fewer lead sinkers introduced to the body of
water.
This is supported by research conducted during the shotgun pellet
debate. Thousands of birds were examined and except for a very few “hot
spots” where a concentrated fishing effort occurred in waters frequented
by bottom feeding birds, the incidence of ingested lead sinkers by
waterfowl was incidental to non-existent.2

A Note On Management
A central tenant of fish and wildlife management is management for
the optimal overall population level, not for the well being of any one
individual. Simply put, sustaining populations is the goal of fisheries
and wildlife management, not sustaining individuals. Mortality caused
by human factors certainly can and should be controlled where necessary
to benefit the health of a population. In populations of all living
organisms there are known causes of mortality that contribute to the
dynamics of the population. Some types are compensatory while others
are supplemental. When a specific mortality level that is caused by man
and can be controlled is a demonstrated threat to the sustainability of
that species or group of species (an example of supplemental mortality),
then action is taken to minimize that threat. The prohibition of lead
shot shells for hunting waterfowl over water is an example of such an
action.

Lead Sinker Impact on Loons
It is not disputed that lead toxicosis may harm or kill loons and
other water birds. This fact is well documented. The pivotal question
is: are loon populations, and populations of other water birds,
significantly reduced by lead sinker ingestion? Or phrased in a more
comprehensive fashion: is mortality from lead toxicosis in loons and
other water birds high enough to threaten self-sustaining loon
populations? Based on available research the answer to both of these
questions is no.
This determination is based on a comprehensive 1999 study
requested by the U.S. Fish and Wildlife Service, Division of Federal Aid
and conducted by the National Wildlife Health Research Center in
Madison, Wisconsin. In this under- reported study, liver, blood,
stomach, and radiograph samples were taken from 2,749 individual birds
of 30 species, a significantly greater sample size than Pokrus studied.
In addition, necropsy records of 36,671 waterbirds and bald eagles
(Haliaeetus leucocephalus) from the files of the National Wildlife
Health Center from the years 1975 through 1999 were examined.
The results showed that only 3.5% of common loons (from a sample
of 313) had ingested lead sinkers and just 27 of 36,671 waterbird and
bald eagle carcasses (0.007%) contained ingested lead sinkers 3
The Fish and Wildlife Service study went on to reexamine the
results of the Pokrus research on loons and lead sinker ingestion as
well as five other related studies. The determination was that “[t]hese
data are insufficient to evaluate the role of lead poisoning as a
proportional cause of mortality in this species, or its role in
population dynamics. Likewise, there is insufficient data to understand
the importance of this form of lead poisoning in other species in which
it has been documented in the U.S?”
Lead poisoning, when occurring in larger birds, causes the bird to be
more noticeable, more vulnerable to capture, and more likely to be
brought forward for examination, thus causing examination in a
disproportionate frequency in relation to the actual mortality of the
population. 2 Samples collected over a wide geographic area and
involving many specimens, such as occurred in the National Wildlife
Health Center report, provide a more accurate profile of the actual
occurrences in the wild.
An examination of the proceedings of a symposium given at the 115th
meeting of the American Ornithologists’ Union in August of 1997 further
bolsters the conclusion that lead sinker ingestion is not a significant
factor in the health of common loon populations. 4
· The largest U.S. breeding populations are found in Minnesota (over
4,600 pairs) and range to just over 100 territorial pairs in New
York, Michigan, and New Hampshire.
· Canada (being the core of the breeding range) has the largest
number of pairs (213,400).
· The population trend of common loons in the U.S. is stable to
increasing in 12 of the 14 states where pairs occur.
· The two states where the population is decreasing are Michigan and
Montana.
· In the United States loon populations are increasing in areas
where they were extirpated and recolonizing in the New England
states.

In the two states where decreasing populations were noted there are
significant points to consider. In Michigan non-breeding pairs
congregate from the entire Great Lakes region and this results in a
larger number of adult loons summering in Michigan as unpaired,
therefore not counted in the Michigan data of territorial pairs. Within
the breeding range of the common loon, Montana’s population is
disjunctive and most loon habitat is in valleys subject to development
and habitat disturbance.4 This evidence does not support the
proposition that lead sinker ingestion is placing loon populations at
risk.
In a separate request, the National Wildlife Health Center asked
the Arizona Cooperative Fish and Wildlife Research Unit at the
University of Arizona to estimate the impact of lost or discarded
terminal fishing tackle on waterbirds. This limited and smaller scale
study examined 15 sites “to assess the availability of lead sinkers,
other fishing tackle and potentially harmful trash (e.g. plastics) to
waterbirds at selected geographic areas?” It concluded “ecause of
the general lack of evidence of ingestion of sinkers by waterbirds
across the United states, there may be little obvious justification for
a nationwide ban on lead sinkers.” 3

Conclusion
Based on a review of the impact of lead sinkers on water bird
populations, the American Sportfishing Association has found that
insufficient data exists to warrant statewide bans on lead sinkers used
for fishing. Further, the American Sportfishing Association has found
that loon populations in the lower 48 states are stable and increasing
in most cases, but that loon populations are subjected to substantial
threats such as habitat loss through shoreline development.
The American Sportfishing Association acknowledges that lead
toxicosis can kill water birds and lead fishing sinkers may contribute
to this mortality. The American Sportfishing Association recommends that
before further laws are enacted to restrict lead sinkers for fishing on
a statewide basis, sufficient data must exist to demonstrate discarded
lead sinkers are an actual threat to the sustainability of loons or
other water bird populations. The American Sportfishing Association
realizes that certain waters may be “hot spots” for ingestion of sinkers
by water birds and encourages any restrictions of lead sinkers in those
waters to be based on sound science that supports the appropriate action
for that water body.
Furthermore, the American Sportfishing Association continues to
encourage and supports voluntary angler education programs for the use
and proper disposal of lead sinkers and urges state and federal fish and
wildlife agencies to do the same. The American Sportfishing Association
would be pleased to work with any federal or state agency, or the
International Association of Fish and Wildlife Agencies, that wishes to
address this issue.

1 Pokras, M.A. and Chafel. 1992. Lead toxicosis from ingested fishing
sinkers in common loons (Gavia immer) in New England Journal of Zoology
and Wildlife Medicine 23(1):92-97.

2 Peterson, R. M., International Association of Fish and Wildlife
Agencies in comments to the U.S. Environmental Protection Agency on the
proposed rule on lead fishing sinkers. December 1, 1994.

3 U.S. Geological Survey, National Wildlife Health Research Center.
December 1999. Prevalence and effects of lead poisoning resulting from
ingestion of lead fishing sinkers and other fishing tackle on selected
avian species.

4 McIntyre, JW and DC Evers (eds). 2000. Loons: Old history and new
findings. Proceedings of a Symposium from the 1997 meeting, American
Ornithologists’ Union. North American Loon Fund, Holdernes, N.H.