Interpopulation differences of the burrowing shrimp Callichirus major on urban beaches under different levels of fishing pressure
Abstract There is growing concern about the sustainability of burrowing-shrimp fisheries in many coastal areas because of their widespread use as bait and their importance as ecosystem engineers. The response of the target populations to the effect of long-term fishing pressure is still poorly understood. The present study reassessed the growth parameters, size structure and reproductive aspects of an exploited population of Callichirus major in northeastern Brazil, comparing it to a population on a beach where fishing pressure is negligible. The results are also discussed in the light of a previous study at the same site in 1999–2000. Sampling was carried out from September 2015 to May 2017 on two urban sandy beaches. Monthly length (dorsal oval) frequency data were analyzed using the FISAT II software package. Growth parameters were estimated with the ELEFAN I routine, using the von Bertalanffy seasonal growth model. The relationship between fecundity and individual size was estimated by linear regression. The exploited population had individual maximum sizes smaller than both those on the unexploited beach and in the population studied 16 years ago on the same beach. The percentages of ovigerous females were smaller than in 1999, and also differed widely between the two populations, with the exploited-beach population having one-fourth as many ovigerous females. This population showed smaller sizes at sexual maturation and low fecundity, and the females were 20% smaller. This study showed that the observed interpopulational differences in the size structure and reproductive parameters of Callichirus major can be attributed to overfishing, and indicated that the exploited population will tend toward collapse if regulatory measures to limit or prohibit fishing are not implemented.