Determinants of Octolasmis lowei Populations in Spiny Lobster (Panulirus gracilis and Panulirus inflatus) in the Southeastern Gulf of California.

The Gulf of California sustains important fisheries, including those targeting spiny lobsters. Despite their economic importance, little is known about the interactions with their parasites, which play essential roles in ecosystems and can provide information on their hosts with potential fisheries applications. The population dynamics of barnacles of the genus Octolasmis, like those of other parasites, may be influenced by biotic and abiotic factors such as sea surface temperature (SST, °C) and carapace length (CL, mm); however, previously reported patterns remain inconsistent. This study analyzed the factors influencing the prevalence and intensity of Octolasmis lowei in Panulirus gracilis and P. inflatus during the 2024 fishing season. A total of 117 P. gracilis and 804 P. inflatus individuals were collected, measured, and examined for parasite identification. Prevalence and mean intensity were compared among sampling months and lobster species. Monthly SST data were obtained from NASA, and generalized additive models (GAMs) were applied to evaluate the relationship between CL and SST with parasite intensity. Only Octolasmis lowei was identified as a parasitic species. No statistically significant temporal variation in prevalence or mean intensity was detected in P. gracilis, whereas P. inflatus showed a significant increase in both metrics during May compared with most other sampling months. No significant differences in overall infection levels were found between host species. Generalized additive models revealed significant non-linear effects of both carapace length and sea surface temperature on parasite intensity in both lobster species. By integrating parasitological and environmental data, this research provides insights into host-parasite relationships in commercially valuable lobster species and contributes to understanding ecological processes relevant to the sustainable management of marine resources.