A comparative analysis of harvested and unharvested populations of the smooth Venus clam Chionista fluctifraga in the Gulf of California
2022
Chávez-Villalba, Jorge | Castillo-Durán, Ariaana | Arreola Lizárraga, José Alfredo
The shellfishery of the smooth Venus clam Chionista fluctifraga is not regulated in Mexico. Therefore, information on the ecology of this species and the effects of the fishery on its populations is necessary to inform management. We present results from a comparative analysis of the density, biomass, and size structure of smooth Venus clam populations in an area not subjected to harvest (UH) and two areas under harvest (H1 and H2) in Bahía de San Jorge (Gulf of California). The UH population had a density of 20.8 ± 1.4 ind m⁻² and a biomass of 392 ± 39.7 g m⁻² on average; the size range was 3.1–55.5 mm (average 28 ± 15.2 mm), and the predominant size class was 40–50 mm. The H1 and H2 populations had, respectively, densities of 14.5 ± 9.5 and 7 ± 6.8 ind m⁻² and biomass of 123.4 ± 20.4 and 123.6 ± 22.6 g m⁻²; the size ranges were 2.1–49 and 4.3–48.7 mm (averages 24.5 ± 14.3 and 30.1 ± 13.2 mm), and the predominant size classes were 0–10 mm and 40–50 mm. Clams in the three populations show an aggregated distribution and live in medium-fine sands (no significant differences in grain size among sites) with oligotrophic water. Although the densities observed in the harvested sites are relatively high, negative effects of the shellfishery are detected. For example, all clam sizes are being harvested, and clams are no longer found in the uppermost zone in harvested sites, with potential impacts on other species. This poses various threats that, together, may decrease the stability of the intertidal ecosystem and affect productivity.
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