Snow Crab: A Successful Fishery
Michael Chadwick and Mikio Moriyasu

Figure :1 Landed value of eastern Canada snow crab fisheries, 1987-1997.

Introduction
Snow crab in the Maritimes Region is one of Canada´s most successful fisheries. The four reasons for its success include: the high value, the excellence of the science program, the management targets are truly conservative or precautionary, and the consultation process is open and effective. We also briefly discuss the future of the fishing

fishery, which includes increasing effort and a change in environmental conditions that could be unfavourable for snow crab.

Figure 2: Male and female snow crab and the part used for frozen sections.

The High Value of Snow Crab
Landings of snow crab are worth about $200 million (Fig. 1). The sole market is Japan, where snow crab fetch a high price. Quality is the focus of this industry. The animals are caught in baited traps. Each licence in the southern Gulf has a limit of 50 to 150 traps. On average these traps catch about 50 kg of crab per haul. Only mature male crab larger than 95 mm carapace width are kept. Because the traps are carefully designed, there is almost no bycatch of non-target animals. Crab are held in refrigerated conditions until unloading at the plant several hours later. They are then cooked, cleaned, sorted by size, colour and shell condition, packed and frozen. Most crab in the southern Gulf are sold as sections (Fig. 2). The visual presentation of crab is as important as the quality of the meat. Japanese technicians are present at all times in the plants to ensure that only crab of the highest standard are shipped to Japan. Because of this focus on quality, the demand for snow crab has remained high, despite changes in the financial markets.

The Excellence of the Science
The science program has strived to visualize the state of the resource so that fishery managers and fishing industry are able to make informed decisions on the management of this species. Snow crab live on the bottom in fine sediment and don´t move very much and are therefore easily caught by trawl gear. Before the fishery opens, the bottom is sampled at randomly-picked stations using a trawl that digs into the ocean bottom and is able to scoop crab out of the mud. The survey is designed using the same techniques as an opinion poll and is able to estimate the abundance of crab, for all sizes and sexes, including those of commercial size and those that will be of commercial size in the next year or two. Maps are drawn to show the location and density of these different types of crab (Fig. 3). Fishers use the maps to target mature males and to avoid areas that have a high percent of immature or softshell crab.

The design of the survey and the analytical techniques were developed by scientists working in the southern Gulf. The survey has been conducted in this area annually for nearly a decade. We know that the survey is reliable because we are able to follow changes in crab distributions from one year to the next (Fig. 4). The survey in the Gulf indicates that catch and effort data from the fishery are accurate because changes in commercial catch rates closely follow changes in stock biomass (Fig. 5).

We have been able to follow the growth of one complete generation of crab from when small dollar-sized crab were first seen in the survey to their recruitment into the fishery about six years later. We know that another wave of recruitment is about to enter the fishery in the next couple of years. Fishers find the maps are useful and feel that our assessments are reliable. The result is that industry pays for most of the science program.

Part of the success in the partnerhsip between industry and science is that the products are clear. These products include: contour maps of the abundance of females, white or soft-shelled males and hard-shelled males; estimates of exploitable biomass; prediction of future trends in biomass; analysis of in-season observer data; monitoring of white crab by fishing ground; and, analysis of logbooks for distribution of catch, effort and catch rates.

Figure 3: Density contours of exploitable adult snow crab ( 95 mm carapace width) for 1989, 1993 and 1997 trawl surveys

Figure 4: Size frequency distributions of male crab taken during the research surveys in southern Gulf (Area 12), 1988 to 1997

Table 1: Information on the snow crab fishery and science program in the Maritimes Region

Figure 5: Commercial catch rate in the southwestern Gulf of St. Lawrence snow crab fishery compared to the biomass of exploitable crab in the research survey, 1989-1997. About 90% of the annual variation in catch rates can be explained by changes in biomass

Precautionary Management
One of the most important reasons for the success of this fishery is the very clear management target. The number of tonnes of hard-shelled male crab, >95mm carapace width, is clearly identified before the season opens. The target is conservative because female crab are excluded from the fishery and male crab are sexually mature before they reach commercial size. The fishery is conservative because the gear is passive and highly selective, avoiding the unwanted types of crab. The fishery is conservative because it protects commercial-sized but immature crab, which will recruit into the fishery in subsequent years. It is also worth noting that the fishing season occurs when the yield of crab meat and the quality of the shell are at their highest value.

While science provides an estimate of the exploitable biomass, it is industry that decides on the appropriate exploitation rate. The role of industry in the management of this species has been the key to success. Exploitation rates are usually set at about 30%, which means that it would take three years to remove the harvestable biomass. But this value can change by fishing zone.

The true test of a fishery, however, is its performance relative to the management target. Since 1990, the snow crab fishery has achieved and not exceeded its target (Fig. 6), indicating that this fishery has been performing well, at least for the past decade.

An Open Consultation Process
One of the most successful aspects of this fishery is the consultation process. It is no coincidence that comprehensive harvest plans and joint partnerhship agreements were first developed with the snow crab industry. These agreements between Department of Fisheries and Oceans (DFO) and industry define how the fishery will be managed, what science will be done and what criteria will be used for opening and closing fisheries. The framework has always been based on scientific evidence and open dialogue has been essential. During the past year there were 24 public meetings between science staff and the fishing industry. These meetings have included discussions of the survey, sampling, observer programs, and various aspects of the biology of snow crab.

One example of this consultation was a recent initiative to expand fishing effort in eastern Nova Scotia. A pilot survey indicated there were more crab in this area than we thought. Although the survey was preliminary, non-traditional fishers were interested in access. Science led the consultation process by insisting that all issues would be discussed openly around the table. It was decided that the current fishery could lay claim to the part of the sea bottom that had been historically fished. Not surprisingly, this area covered the extent of the pilot survey. The non-traditionals agreed to explore areas outside the traditional grounds. In this sense, snow crab has provided a model on how to set up new fisheries. The secret is to ensure that good information is freely available.

Figure 6: Landings of snow crab compared to the management target (total allowable catch - TAC) for the southern Gulf of St. lawrence, (Area 12)

Figure 7: The areal extent of the bottom waters less than 0°C (yellow) and less than 2°C (red) on the Magdalen Shallows and the northeastern Scotian Shelf during summer in 1990 and 1995. Note the much larger area of cold water in 1995

What About the Future?
Snow crab like cold water; their preferred temperature ranges from 0 to 3 ßC. If waters on the ocean bottom warm up, snow crab could become less abundant. It is quite possible that cold weather during late 1980s and early 1990s allowed the distribution of snow crab to extend outward into the deeper channels of the Gulf of St. Lawrence and southward into the waters off eastern Nova Scotia. It is clear on the enclosed map that cold, bottom water was very extensive during the mid 1990s (Fig. 7). A return to normal and warmer conditions could mark the end of this extended distribution. Because the waters off Cape Breton are at the southern limit of snow crab´s range, the warm temperatures of the last three years may have an impact and the resource may not remain at the levels we see today.

In some ways the success of the science program has brought its own set of problems. The fishing industry has expectations that are greater than the ability of the small science group to deliver. In this light, we need to educate fishers on risks and uncertainties of the survey; we need to spend more time explaining the limitations of our surveys; and we need to link costs of science to the precision of our advice. It needs to be clear that more surveying results in better precision. One approach to increasing precision is to allow more participants in the collection and analysis of the advice. In this regard, we intend to train more people to do mapping and to include uncertainties with our survey maps. Finally, we intend to better publicize the success of this fishery and to show that scientific management of fisheries is not only possible, but is the way of the future.