A comparison of two methods for sampling the Gulf of California mud shrimp, Neotrypaea uncinata (Crustacea: Thalassinidea)

Methods for collecting mud shrimp are highly variable, and the efficiency of these techniques is poorly known. In October 1999, on a mud flat near Puerto Peñasco, Sonora, México, we compared the 'kiwi' method for extracting mud shrimp from their burrows, with a core sampling method designed to accomplish the same goal. The coring method involved pressing a 10 cm × 90 cm PVC pipe into the substratum, creating suction in the pipe, and withdrawing a core of mud and the shrimp within. The kiwi method required 8-10 researchers to march in a circle on the mud flat to gradually liquefy the mud, thereby forcing shrimp to the surface as the circle closed inward. Two transects of 30 cores conducted at high and at low tide yielded similar numbers of adult animals of both sexes. Previous results show that mud shrimp tend to aggregate within burrows when breeding. In this collection, the distribution of mud shrimp in cores did not differ from a Poisson distribution, suggesting that these shrimp were non-reproductive. The kiwi method provided no such information on mud shrimp distributions. Moreover, this method generated significantly fewer intact mud shrimp than were obtained in cores. Our results indicate that compared to the kiwi method, the coring method generates more animals, is less destructive of mud shrimp habitat, and provides more detailed information on mud shrimp populations.