Estimating spatial patchiness of a threatened marine snail based on movement behavior

Normally diffuse animals may group together in patches to facilitate reproduction and enhance survival in the ocean. However, consideration of spatial patchiness is not common in management frameworks, which often use mean abundances instead. Animals, such as queen conch (Aliger gigas), that congregate in patches at high density are often heavily harvested, resulting in overexploitation. To better understand the drivers of spatial heterogeneity in conch distributions, we used biologgers to quantify movement behavior, including activity rates, environmental effects, and short-term dispersal. We used the resulting values to model conch dispersal in breeding areas. Distance to next encounter analyses described how much space separated patches of conch, where a patch is any area containing conch. Results of field surveys were combined with conch dispersal estimates to compute the frequency of occurrence of patches, patch length, and population density of conch in patches across hundreds of kilometers. Most conch occurred in aggregations, defined as patches with multiple conch. Most surveys in areas with fishing pressure were devoid of conch and conch aggregations, reinforcing that mean population density can be a misleading management indicator. However, behavior provides an alternative context to inform conch management because patch sizes and conch density in aggregations where reproductive activity was observed were consistent in our study area. Breeding aggregations rarely occurred in patches longer than 330 m and thus often occupied areas small enough to be managed by local governance, suggesting small-scale spatial interventions offer a pathway to conservation for patchily distributed species. Our species-specific results suggest the minimum space needed to protect an aggregation and underscore the versatility of using movement ecology to inform conservation.