Effects of land-use/land-cover changes on land crab,Cardisoma guanhumi, abundance in Puerto Rico

Abstract

The land crabCardisoma guanhumipopulations have been on the decline in Puerto Rico for the last three decades. While some studies suggest overexploitation and pesticides as causing the observed population declines, the effect of land-use/land-cover (LULC) changes have not been investigated. In this study we compared the abundance and size ofCardisoma guanhumiin five different LULC types (mangroves, grasslands, forest, urban and industrial), and investigated the relationship between differences in physical microhabitat conditions among the LULC types with crab abundance and size. Although no significant differences in size were found among the different LULC types, crabs were significantly less abundant in grassland sites. Surface soil temperature, depth to groundwater and air temperature were found to vary significantly among the LULC types. Of these, only surface soil temperatures had a significant negative relationship with crab abundance. It appears that high variation in soil temperature and a high groundwater table observed in the grasslands is most detrimental to crabs. Interestingly, during the time when land crab populations declined there was corresponding change of LULC from agriculture to grasslands.Cardisoma guanhumiis resilient to changes in LULC, however, changes that alter their access to groundwater and escape from high soil temperature reduce their habitat.

Local distribution and abundance of Cardisoma guanhumi Latreille, 1928 (Brachyura: Gecarcinidae) in southern Brazil

“…In the forested areas, these burrows are less densely packed. C. guanhumi population tends to suffer a reducing process in grass, probably because there is high temperature variance and restricted access to ground water in this site (Govender et al, 2008). The same phenomenon was verified in our study.…”

Mitochondrial DNA Variation Reveals a Sharp Genetic Break within the Distribution of the Blue Land Crab Cardisoma guanhumi in the Western Central Atlantic

“…The species is intensively exploited as a food resource in many countries along the Atlantic coast of Central and South America, particularly Puerto Rico, the Bahamas, Honduras, Columbia, Venezuela, and Northeast Brazil [7,8,9,10], which has led to increase pressure on overfishing, and therefore, contributing to unsustainable fisheries throughout its distribution range. Consequently, crab fisheries have been declining along with species abundance in many countries [11,12,13], mainly due to unsustainable catch levels ( i.e. , overexploitation) and ongoing habitat degradation.…”

Fine-scale genetic structuring, divergent selection, and conservation prospects for the overexploited crab (Cardisoma guanhumi) in tropical mangroves from North-eastern Brazil

“…The percentage of polymorphic loci observed in Cardisoma guanhumi (P ¼ 93.4%) was significantly higher than those reported for other species (Ucides cordatus; Ocypodidae (ISSR: P ¼ 80%; Britto et al, 2011); Artemia urmiana; Artemiidae (ISSR: P ¼ 65.8%; Eimanifar & Wink, 2013) Pannacciulli et al, 2009)). Despite the evidence of Cardisoma guanhumi population reductions due to overfishing and habitat loss (Amaral & Jablonski, 2005;Govender et al, 2008;Rodríguez-Fourquet & Sabat, 2009;IBAMA, 2014), greater adaptive potential (genetic variation) of Cardisoma guanhumi was identified from this tropical mangrove system, when compared with other shellfish equally exploited and/or living in affected areas. Besides, no significant differences were found between the levels of genetic diversity of the species in each sampled mangrove, despite the different levels of conservation observed among the mangroves from the north and central (most affected), and south (less affected) coastlines.…”

“…In recent decades, Cardisoma guanhumi has experienced a sharp population decline by overfishing owing to the loss and/or degradation of habitat (Amaral & Jablonski, 2005; Rodríguez-Fourquet & Sabat, 2009). Studies have shown that in areas where fishing is allowed, many populations are classified as juveniles suggesting their low survival rate (Botelho et al ., 2001; Govender et al ., 2008; Shinozaki-Mendes et al ., 2013). Besides, Cardisoma guanhumi has been found to be sensitive to changes in the water quality resulting from the discharge of domestic effluents, industrial or agricultural effluents, and aquaculture (Galli et al ., 2012).…”