Seals And Cod

A Canadian council known as the FRCC (Fisheries Resource Conservation Council) studies fish and seal population, and advises the Minister of Fisheries and Ocean on population and conservation steps they believe need to be taken. In an April 1999 paper (http://www.ncr.dfo.ca/frcc/1999/frccr199.pdf), they advised that seal populations needed to be culled by up to 50% of the levels at that point. One might ask why. They believe that preventive action is necessary to ensure groundfinsh populations, particularly cod, remain adequate without waiting for definitive scientific proof. In other words, let’s take corrective measures now, before the seals eat all the fish. So the question is, what exactly is driving this issue, and why should we start exterminating seals?

Cod

An assistance program, the Northern Cod Adjustment and Recovery Program (NCARP) accompanied the closure, initially expected to be for two years. NCARP provided an income supplement and retraining opportunities for affected fishermen as well as incentives to reduce fishing capacity. When Canada extended fisheries jurisdiction in 1977, following a period of extensive overfishing by foreign fleets, cod stocks rebounded dramatically in three to five years. This time, with the exception of the south coast of Newfoundland, where seals coincidentally are not abundant, recovery of cod stocks has been extremely slow. The moratorium was subsequently extended and the NCARP program was replaced by The Atlantic Groundfish Strategy (TAGS) which continued income supplements and adjustment measures, for some fishermen, until 1999.

An acrimonious debate ensued on the causes of the collapse of the stock. The Northwest Atlantic Fisheries Organization (NAFO) Scientific Council view and the consensus view of Department of Fisheries and Oceans (DFO) scientists was that the decline had been rapid and a number of factors contributed to it, including overfishing, harsh environmental conditions and, possibly, to some extent, increased predation of seals on cod. Others strongly held the view that the decline had been gradual over nearly 10 years and was entirely due to overfishing which had gone unnoticed by scientists. No scientist has claimed that seal predation was a major factor in the collapse of northern cod, but there is evidence that seals may be a factor in the slow recovery of northern cod and other cod stocks.

In the following three years most of the cod fisheries in Atlantic Canada were closed, together with fisheries for other groundfish, due to low abundance and low productivity of the stocks. Monitoring of the northern cod stock by research vessel surveys showed that the stock continued to decline until 1994. This was unexpected and devastating news.

After the cod fisheries were closed, only small amounts of cod were taken incidentally in fisheries for other species but, in several stocks, research vessel surveys and sentinel surveys by fishermen showed that surprisingly few cod were surviving from year to year. Evidently, natural mortality had increased substantially from the levels of the 1970s and early 1980s. Why did natural mortality increase? One possibility was unfavorable environmental conditions. During the early 1990s the northwest Atlantic was exceptionally cold, with large areas of sea bottom normally frequented by cod covered with sub-zero water. Sampling off Labrador and in the northern Gulf of St. Lawrence found cod in very poor condition, particularly in 1992 and 1993. Energy reserves were so low that many cod may not have survived the winters of 1992-93 and 1993-94. Another possibility also receiving increasing attention was predation by seals on cod.

Seals

The emergence of new markets in the mid-1990s led to increased harvests from 1995 on, more or less stabilizing the size of the harp seal herd. The most recent assessment of Atlantic Canadian harp seals, in 1999, found that they now number over 5 million, more than twice their numbers in the 1960-80 period.

Hooded seals number about 600 thousand in the northwest Atlantic. Third in abundance are grey seals, at about 200 thousand. Hooded and grey seal herds have been increasing for at least 15 years. Harbour seals are less abundant at about 30 thousand. Some ringed seals and bearded seals are seen off Labrador and northern Newfoundland in the winter.

What are the implications for cod of the presence of millions of seals in Atlantic Canada?

Seals eat fish

Seals eat large amounts of fish and marine invertebrates such as shrimp. Direct estimates of the prey consumed by millions of seals dispersed over the northwest Atlantic are not practical, but rough measures can be obtained indirectly. Feeding seals under laboratory conditions has revealed their annual food energy requirements. For a harp seal, this is one to one and one half tonnes of food per year, depending on the energy content of the prey. Fatty fishes like caplin have high energy content whereas shrimp have much less energy per unit of weight. If seals are shot for samples, the contents of their stomachs can be examined to determine what they have eaten. Undigested hard parts of fish, particularly the ear bones or otoliths can identify the species and size of prey consumed. By scaling up the diet composition observed from stomach samples to account for the energy requirements of a seal herd for the period it is found in southern Canadian waters, scientists obtain an estimate of the quantities of prey consumed.

Harp seals have been the most extensively studied. Five million harp seals consume about seven million tonnes of food per year, but much of this occurs in the Arctic or involves non-commercial or lightly fished species such as arctic cod and caplin. An estimated three million tonnes of fish and invertebrates was consumed by harp seals in waters south of mid-Labrador in 1996 with similar amounts in subsequent years. Cod represents only a small percentage of harp seals’ diet. The most recent (1999) estimates of the quantities of cod consumed are about 100 thousand tonnes, with 50-60 thousand tonnes being northern cod. Surprisingly, despite the low abundance of cod in the 1990s, seal stomachs show more cod consumed, in total, during this period than in the 1980s. Also there is evidence of signi-ficant amounts of cod up to seven years old consumed, while in previous decades, few cod older than two years were found in harp seal stomachs. These estimates are very rough and may have significant biases, for example when seals eat only soft parts of cod as has been observed in Newfoundland, stomach samples do not reflect such predation. Despite the uncertainties and possible biases, it is clear that harp seals are consuming more northern cod and more cod in the northern Gulf of St. Lawrence than fishermen are catching. The total allowable catch for northern cod in 1999 was only nine thousand tonnes, less than 20 percent of corresponding predation by harp seals.

Other seal species also consume cod. The amounts consumed by the much larger grey seals are almost half as much as by the far more abundant harp seal. This reflects the greater percentage of cod in the diet of the grey seal, the greater energy requirements of a larger animal and its year-round presence in areas where cod are found.

In 1999, for the first time, scientists incorporated estimated consumption of cod by seals in the assessment of cod in the northern Gulf of St. Lawrence. In their analysis, seal predation was a major source of mortality for cod in the 1990s.

The science of predator culls

While scientists generally agree on the abundance of harp seals and that the amount of cod they consume is substantial, they also agree that the implications of reducing seal herds are uncertain. Reducing the amount of cod consumed by seals will not necessarily result in more rapid recovery of cod stocks.

Experience with predator culls has sometimes been surprising. In the early 1920s, pumas, coyotes and wolves were removed from the Kaibab plateau in Arizona to increase the deer herd they preyed upon. The herd increased to over 100 thousand, overgrazed their habitat causing long term damage and fell back to less than 10 thousand instead of the anticipated 30 thousand which motivated the predator cull. Experimental removal of one species of starfish from a rocky intertidal zone in Washington State led to a diverse community of molluscs, barnacles and snails being replaced by only blue mussels and goose-necked barnacles, not the most desired species for commercial harvest.

Scientists opposed to a seal cull point out that there may be other species consumed by seals which also predate on cod, so reducing seal abundance may increase other predation, nullifying or reversing the expected benefit. Also, if cod became twice as abundant while seals were half as abundant as now, seals might still consume the same amount of cod because they might encounter more cod and it could become a higher proportion of the seal diet.

Stakeholder views

The FRCC regularly consults fishermen and the public before formulating their conservation recommendations. Consultations in most of Atlantic Canada have seen many impassioned pleas to reduce the seal herds in order to favour the recovery of cod stocks. The Honourable John Efford, Minister of Fisheries and Aquaculture for Newfoundland, has been outspoken in calling for immediate action to reduce seal herds. However, the seal catching folks are against any thinning of the seal population as it would mean fewer resources for them to exploit. In addition, the less than favorable publicity would lead to a reduction in product demand, thus reducing their profits. Another point to consider is that PETA and NGO’s like the IFAW (International Fund for Animal Welfare) put forth the position that fisheries have never been improved as a result of a cull.

The House of Commons Standing Committee on Fisheries and Oceans, in June 1999, believed that “there must be a major reduction in the harp seal population” and called for a “panel of eminent persons to evaluate the current state of scientific knowledge and to plan a long term strategy for the management of seal populations” (http://www.parl.gc.ca/InfoComDoc/36/1/fish/Studies/Reports/fishrp13-e.htm ).

A policy dilemma

Although years of research have established many facts, the science of seals and cod is inconclusive and will remain so for the foreseeable future. Seals are a significant source of mortality for northern cod and northern Gulf of St. Lawrence cod. The seal herd would not be put at risk by a reduction to, say, 2 1/2 million from 5 million. The cod are depleted, so much so that the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) declared Atlantic cod vulnerable in 1998. Nevertheless, reducing the abundance of harp seals may or may not lead to more rapid recovery of depleted cod stocks.

Should the precautionary approach apply here to reduce abundant seal herds even if there is no certainty that cod stocks will benefit? As defined at the United Nations Conference on Environment and Development, the precautionary principle states: The principle is usually applied in a context of restraining human activities, such as pollution in order to protect the environment and ecosystems. In this case man would intervene to change the balance of species in an ecosystem so as to protect threatened cod stocks.The general idea for managing fish culls in the UNFA (United Nations Fisheries Agreement) and more recently Canadian techniques, calls for stronger measures protecting fish stock levels, rather than allowing Fishermen to capture as many as possible. In principle, the precautionary approach could be applied to intervene in a natural ecosystem, but this would be a very unusual application.

The effects of reducing the seal herds are highly uncertain and there would be potentially large costs, beyond the cost of a cull. Seal culls that aim to reduce a herd without utilization of the resulting carcasses are highly controversial. A major cull could lead to a widespread negative reaction worldwide, reducing Canada’s prestige and possibly leading to trade boycotts as well as damaging markets for seal products. While many people, particularly in Atlantic Canada, consider the evidence strong enough to justify experimentally reducing seal herds by an expanded hunt to learn whether cod stocks will recover, few advocate a cull involving killing seals without utilizing the pelts and carcasses. In a sense, the potential backlash is considered too great for such a cull to be “cost effective.”

In the past, the policy response to this dilemma has been to postpone action and do more research in the hope that a consensus among scientists would either justify reducing seal herds or discredit the idea. Such a consensus remains elusive. The FRCC recommendation has introduced a new factor: a call for action before the supporting science is conclusive. Their rationale is understandable, from the viewpoint of promoting recovery of cod stocks but the policy decision has not become easier.

In December 1999, the Minister of Fisheries and Oceans, the Honourable Herb Dhaliwhal, announced that he concurred with the recommendation of the Standing Committee on Fisheries and Oceans. He agreed to appoint a panel of eminent persons to provide advice on a new long term strategy for the management of seal populations.

Read more: http://isuma.net/v02n04/huebert/huebert_e.shtml


Note

* William G. Doubleday is Senior Visiting Fellow (Science and Technology), Canadian Centre for Management Development (CCMD).