Skate Bathyraja spp. egg predation in the eastern Bering Sea

Area of Science:

• Marine Biology
• Ecology
• Ichthyology

Background:

• Skate egg predation by snails is a significant factor in elasmobranch population dynamics.
• Understanding these interactions is crucial for conservation efforts in the eastern Bering Sea.

Purpose of the Study:

• To investigate snail predation rates on eggs of three skate species (Alaska skate, Aleutian skate, Bering skate) across different nursery sites.
• To determine the influence of geographic region, egg-case density, and snail density on predation levels.

Main Methods:

• Field surveys were conducted at seven nursery sites in the eastern Bering Sea.
• Predation levels were quantified by examining skate egg cases for snail-induced damage.
• Snail abundance and egg-case densities were recorded.
• Morphological analysis of drill holes in egg cases was performed.

Main Results:

• Predation rates varied significantly among skate species, with Bering skate (22.25%) experiencing higher predation than Alaska skate (6.46%) and Aleutian skate (2.65%).
• Predation was higher in northern and middle regions compared to southern regions.
• Predation decreased with increasing egg-case density and increased with snail density.
• The Oregon triton (Fusitriton oregonensis) was the most abundant predator, and egg case morphology (spines on Aleutian skate) appeared to influence predation susceptibility.

Conclusions:

• Snail predation on skate eggs is spatially variable and influenced by ecological factors and species-specific traits.
• Egg case morphology, particularly the presence of spines, may offer protection against snail drilling.
• Management strategies should consider regional differences in predation pressure and habitat characteristics.