Abstract
The red sea urchin fishery has a long harvest and management history along the Northeastern Pacific coast. In Mexico, it has been commercially harvested since 1972, and although it is one of the most important fisheries in Baja California, efforts to assess the condition and dynamics of harvestable stocks have been focused on certain harvested areas with scarce fisheries independent data. Additionally, the analysis of yearly information for small geographic areas has obscured the actual status of harvested populations. This study aims to re-assess population trends, fishing effort, and catches, incorporating all available information from the last 19 years. Information was grouped based on 14 landing sites along Baja California’s Pacific coast. Length based virtual population analysis (LVPA) was implemented to estimate site-specific catch rates and densities. Red sea urchin catches / landings varied widely within and between areas. Average population density for the region reflects higher recruit values (≈2.5 urchin m-2); density of reproductive juveniles/adults averaged 0.79 (SE ± 0.04) urchins m-2; while estimated density of adults was lowest, with only 0.26 (SE ± 0.01). LVPA produced biomass estimations that double previous estimates. We suggest that the model parameters used in previous estimations might not reflect key biological traits of the red sea urchin, failing to reproduce population trends accurately. Based on current estimations, there is no apparent stock decline in areas where catches/landings are high; there, consistent settlement/recruitment may partially mitigate for fishery removals. New management measures must be adopted: maximum legal size of 110 mm, continuous fishery independent surveys, improvement on fishery logs and analysis, and tracking red sea urchin density, as means to track changes in the population that might not be so apparent when observing only catch/biomass data. Reinforce the under legal size urchins since results suggest that sites with high abundances of small urchins can support higher catches.
Highlights
Red sea urchins (Mesocentrotus franciscanus) are one of the must-studied echinoderms in the Northeaster Pacific coast, from Mexico to Alaska (Ebert et al, 2018)
Catch was highly variable depending on site, with highest catches, above average most of the years, at ST, PBaj, AS, and Punta Banda (PBan)
Observed variability could be related to urchin availability and to number of permit holders operating in each area, fishable days due to weather conditions, divers’ willingness to work and endurance, co-op internal agreements, and market conditions
Summary
Red sea urchins (Mesocentrotus franciscanus) are one of the must-studied echinoderms in the Northeaster Pacific coast, from Mexico to Alaska (Ebert et al, 2018). The first official regulations emerged in 1993, and consisted on limited effort (one diver per vessel), fishing seasons based on reproductive peaks (closed from March to July each year), exclusive fishing areas, total allowable permits, fishing logs, minimum urchin density for fishing sites, minimum legal harvest size (80 mm and up) based on unpublished reproduction studies (Tapia, 1986; Ruiz et al, 1987), and even individual catch quotas. All these regulations, but the quotas, have been kept in place since, with little or no modifications. Main findings attempt to provide an integrated tool for better managing this important fishery
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