Beyond the obvious: Population characteristics of the ghost shrimp <i>Callichirus corruptus</i> (Hernáez, Miranda, Rio &amp; Pinheiro, 2022) (Decapoda: Axiidea: Callichiridae) vary across beach zones

Abstract We investigated whether population attributes of the ghost shrimp Callichirus corruptus (Hernáez, Miranda, Rio &amp; Pinheiro, 2022) vary between different intertidal zones and explored the methodological implications of these variations. Sampling was conducted on three beaches in northern Rio de Janeiro state, Brazil. Sex ratio, age structure, abundance, sampling effectiveness, body size, and condition factor (K) were assessed between different intertidal zones. The results revealed significant differences in sex ratio, age structure, and population density between zones, with the highest burrow density observed in mid-intertidal zones. Adult populations were prevalent in all zones, although the degree of sex-ratio bias varied, with a higher proportion of females in zones further away from the water, close to the high-tide line. Although catchability did not differ significantly between zones, the condition factor varied with sex, age, and beach, but was not affected by zonation. These findings highlight the role of physical heterogeneity in shaping the spatial distribution and population structure of C. corruptus. Balanced sampling across intertidal zones is necessary to avoid biased assessment of population dynamics.