From descriptive to accurate horseshoe crab size variations in wild populations

Abstract

Horseshoe crabs have survived until Holocene, but their persistence beyond the Anthropocene is challenged by drastic environment changes that entail impoverishments and the resultant unusual growth sizes. Previously, allometry via morphometric ratio was introduced to classify horseshoe crabs into normal-abnormal growth. However, the descriptive size and weight analysis indicated a considerable portion of Tachypleus gigas with normal allometry. This error was caused by the median sorting of values. Therefore, the same data was treated with correlation before generating a linear equation. By being sexual dimorphs, these arthropods actually have gender-specific morphology indicators which could generate a functional allometry. Since the assessed arthropods were mature, the 19 % yield of smaller female T. gigas was possibly due to degradation effects from poor diets or stress. Yet, for this population, an added risk was female-only harvest. Perhaps, close sizing to male counterparts could be perceived a survival strategy by the female T. gigas. More evidence is needed to strengthen this opinion but for now, this assessment method is novel for accurate allometry assessments in the species with sexual dimorphism. Overall, capture fisheries could have negative impacts and when made severe by sex-specific harvest, the unaccounted practices could collapse sustaining populations.