South Africa's fisheries play an integral role in many of its coastal regions' local economies, and are the lifeblood of many communities. In the 1960s, South Africa implemented total allowable catch (TAC) rates and individual quotas to control the amount of sea life that could be removed from certain regions in an effort to ensure the sustainability of its resources for future generations. Unfortunately, many of these policies were based on assumptions rather than on quantitative scientific analysis.
In 1990, the West Coast Rock Lobster Fishery experienced a sudden downturn in commercial catch rates. More than 80 percent of captured lobsters failed to meet the government's 89 mm minimum carapace size requirement and had to be thrown back into the ocean. Also, bait usage increased well beyond normal levels. At the time, government scientists believed that the shortage resulted from a sharp decline in the lobster's growth rate, which was likely due to lack of mussels, the lobster's main food source.
Dr. Amos Barkai and Dr. Mike Bergh of the Ocean and Land Resource Assessment Consultants (OLRAC), an independent consulting organization, were contracted by the South African West Coast Rock Lobster Association to assess the state of the rock lobster stock and provide recommendations on sustaining it long term.
OLRAC conducted intense fieldwork and used SPSS® for computer-based quantitative analysis. Through its research it found that some of the fishery's problems correlated to the strict adherence to its minimum 89 mm size requirement. The data suggested that, by setting a high minimum catch size, the lobsters' growth rate might have slowed as strong and fast growing lobsters were continuously removed from the sea. Also, undersized lobsters incurred injuries as fisherman frequently caught and discarded them. Based on its findings, OLRAC worked with the South African government to lower the minimum catch size to 75 mm.
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Armed with variables ranging from water temperature to latitude and decades of fishing data, Drs. Amos Barkai and Mike Bergh helped South Africa balance local communities' economic dependence on the fishing industry with the sustainability of South Africa's natural resources. For more than a decade, OLRAC has influenced South African Fishery policy, not by lobbying, but by providing objective and quantitative scientific analysis of fishing trends.
OLRAC, an independent consulting organization, gained prominence in 1990 when the South African West Coast Rock Lobster Fishery experienced extremely low catch rates that threatened to cripple the industry. Many captured lobsters fell below the government's established 89 mm minimum catch size. Subsequently, catch rates rapidly became uneconomical, bait usage increased by many times its normal level, and the percentage of lobsters thrown back exceeded 80 percent of the total catch weight in many areas.
Like many businesses, the South African West Coast Rock Lobster Fishery faced a serious economic challenge — how to boost supply and meet demand without eliminating a key resource. The issue was further complicated by the fact that government scientists attributed the lobster shortage to the lack of mussels, the lobster's main food source. OLRAC set out to determine if other factors contributed to the decline by using SPSS Base and its data analysis capabilities.
According to Dr. Barkai, "SPSS' ease of use made it particularly valuable because the analysis is carried out by non-mathematical individuals who need easy access to sophisticated statistical capabilities." In addition to using the large commercial catch database, OLRAC gathered data by conducting diving and fishing surveys to determine the lobster population in given areas, and then incorporated historical data on lobster population growth. Lobsters have been captured, tagged and released before and after their yearly molting cycle since 1968.
OLRAC also considered other variables, including temporal and spatial factors such as time of day, latitude, longitude, water depth, weather conditions (both atmospheric and oceanographic) and the state of the tide and moon.
In some cases, there were gaps in historical data regarding when and where lobsters were tagged. To fill the holes, Drs. Barkai and Bergh used SPSS Base Module and the SPSS General Linear Model (GLM) utility to identify potential biasing factors in historic catch rate trends. They also used these tools to produce a catch rate time series, which can be use as an unbiased indicator of trends in resource size.
"The commercial interest in the analysis' results and the near-, medium- and long-term trends and estimates for each year is considerable, since it is the primary information used in computing a TAC," said Dr. Bergh. "If the analysis reveals an overall decline in lobsters over time, then it implies that the resource is being managed on a non-sustainable basis and, consequently, the impact of the fishery on the resource should be reduced."
Based on intensive research, OLRAC's work confirmed that lobsters' yearly growth sizes had dropped dramatically prior to the sharp decline in their catch rate, resulting in the lobsters not reaching the 89 mm catch size quickly enough. As government scientists suspected, their growth rate retardation may have been partially due to the lack of mussels. However, data analysis with SPSS Base suggested that the high level of lobster discarding was the primary factor to blame for the poor growth rate and high level of fishing-related lobster mortality.
SPSS' ease of use made it particularly valuable, because the analysis is carried out by non-mathematical individuals who need easy access to sophisticated statistical capabilities.
Dr. Amos Barkai
Director and Head of Software Development Unit
Ocean and Land Resource Assessment Consultants
Using computer-based quantitative analysis as the foundation for its recommendations, OLRAC worked with the South African government to reduce the minimum catch size to 75 mm. The size reduction, in conjunction with a carefully controlled TAC, resulted in an immediate and sharp increase in catch rates. In fact, catch rates have doubled since 1994. The lobster population has also showed strong signs of recovery, due in part to the virtual elimination of the discarding and injuring of lobsters.
With a successful resurgence in the lobster population, the scientific working group convened by the South African government recognized that OLRAC's research played a critical role in determining fishery policy. As a result, OLRAC now participates in all the scientific deliberations leading to the annual TAC for several South African fisheries. It has conducted a large number of field experimental studies and independent fishing surveys, and has modernized the scientific approach to the fisheries' management of its resources by developing specialized computer models.
"Fishery management must address the trade-off between economic risk and biological risk, it must be practical, and it must allow consideration of the logistics of fishing, targeting and market requirements to influence one's interpretation of basic-catch statistics," said Dr. Barkai.
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