Species Composition and Morphological Variation of Crayfish in the Gault Nature Reserv

Abstract

Crayfish play a crucial role as ecosystem engineers in freshwater ecosystems, yet they remain poorly represented in ecological studies. Integrating aquatic invertebrates into biodiversity monitoring efforts is urgentlyneeded, particularly given their important ecological role as indicators of freshwater ecosystem health. The purpose of this pilot study was to record crayfish presence in the Gault Nature Reserve and to characterize species identity, morphology, and dorsal colouration of individuals from two habitats sampled (Lake Hertel and a nearby stream), with colouration assessed for substrate matching. This study records the occurrence of two crayfish species in the Gault Nature Reserve of McGill University and examines their morphological and colouration differences. Two species of crayfish were identified: the Virile crayfish (Faxonius virilis) in Lake Hertel and the Appalachian Brook crayfish (Cambarus bartonii) in a nearby stream. A key outcome of this pilot survey is the identification of different crayfish species living in different habitat types within the reserve. This finding demonstrates the necessity of broader biodiversity surveys of freshwater species in Gault. Morphometric analyses showed significant size differences between species aligning with ecological differences observed between the two site-specific species, though these disparities likely reflect species–specific traits more than habitat effects alone, which could not be isolated in this study design. Colouration analyses did not support the hypothesis that crayfish colouration matches substrate colours for camouflage. The analysis of colouration is considered exploratory and must not be considered a conclusive test of substrate matching because of the failure of photographic colour extraction to match colouration and the absence of consideration of body size sex, and developmental stages. Future research should incorporate more controlled colour assessments, expand the survey area, and conduct genetic analyses and transplant experiments to clarify whether colouration and morphology are determined by environmental or genetic factors.