|Scientific Name:||Diplobatis guamachensis Martín Salazar, 1957|
|Taxonomic Notes:||The species is distinguished from the sympatric Diplobatis colombiensis in that it presents brown bands running longitudinally on the edges of the disc and the pelvic fins and transversely on the body and tail; bands vary in thickness but never exceed 0.5 times the diameter of the eye.|
|Red List Category & Criteria:||Vulnerable A2bd+3bd+4bd ver 3.1|
|Assessor(s):||Caldas, J.P., de Carvalho, M.R. & McCord, M.E.|
|Reviewer(s):||Heupel, M.R., Kyne, P.M. & Fowler, S.L. (Shark Red List Authority)|
Diplobatis guamachensis has a restricted distribution in the Western Central Atlantic, where it is known only from Trinidad, Venezuela and northeastern Colombia, occurring in depths of 30 to 183 m. Little information is available on this small (to 21 cm total length) batoid, and information concerning biology, population dynamics and status are generally lacking. It is, however, considered to be common in parts of its range. The brownband numbfish is sympatric with Diplobatis colombiensis in part of its Colombian range and, due to identification difficulties between these species, it may be more heavily fished than currently thought. However, most of the range of D. guamachensis is distinct from that of D. colombiensis. The species is taken as bycatch in trawl fisheries and the genus Diplobatis has been shown to have a 27.5% occurrence in the captures from offshore trawl fishing in Colombia. Even though little information is available on the species, it is assigned the category of Vulnerable as a precautionary measure given its restricted regional distribution in generally heavily trawled areas.
|Range Description:||Recorded from the Gulf of Venezuela, western Trinidad, and northeastern Colombia.|
Native:Colombia; Trinidad and Tobago; Venezuela, Bolivarian Republic of
|FAO Marine Fishing Areas:|
Atlantic – western central
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Cervigón and Alcalá (1999) described this species as common in its distribution area. McEachran (1984) reported the highest abundance from the western area of its distribution, where Valdez and Aguilera (1987) reported that it was always captured in research surveys. |
Caldas et al. (in prep.) show evidence of intra-populational variation in coloration patterns and geographic range for specimens collected throughout the northern coast of Colombia. There are shared areas (Tayrona National Natural Park-La Guajira) for D. colombiensis and D. guamachensis, where individuals show a particular color pattern that is intermediate between its own characteristics and that of the related species. It is important to note the presence of a morph of D. guamachensis in the area of Tayrona National Natural Park, a zone where only D. colombiensis had been previously reported. This supports the idea that populations of this species may be genetically mixed in some areas, resulting in interaction between specimens with specific characteristics that are combined. Similar situations may be possible in other regions shared by D. guamachensis and D. colombiensis (e.g., Trinidad).
|Current Population Trend:||Unknown|
|Habitat and Ecology:||This species is benthic on the continental shelf at depths of 30 to 183 m (McEachran and Carvalho 2002). The region inhabited by D. guamachensis is characterized by hard sand with extensive coral reef development in some areas. This is contrary to reports by Cervigón and Alcalá (1999), who stated that it is very rare to find this species in coral reef areas. The substrate in the region appears to determine the development of the various color patterns (Fechhelm and McEachran 1984). |
Very little known of the species' biology. Reaches a maximum size of ~20 cm TL (McEachran and Carvalho 2002) and maturity in males is estimated to be 12 cm TL (Caldas et al. in prep.).
Demersal trawl fisheries operate over the species' limited area of occurrence. Medina (2002) reports Diplobatis pictus as bycatch in shrimp trawl fisheries in Colombia. These catch surveys were in the geographic range of both D. guamachensis and D. colombiensis, and so specific information on D. guamachensis is not available (D. pictus does not occur in Colombia, being known from southeastern Venezuela to northern Brazil).
Because of identification problems, the species may be more frequently caught than suspected.
|Conservation Actions:||An adequate conservation program for the Colombian Guajira peninsula is needed. This area supports extraordinary species richness, including several southern Caribbean endemics. Plans for developing and exploiting mineral resources in the Guajira continental shelf and slope during the 21st century must consider this fact (Caldas et al. in prep.).|
Caldas, J.P., Acero, A. and Mejia, L.S. (in prep.) Evidence of sympatric distribution in the Dwarf electric rays of the genus Diplobatis (Torpediniformes: Narcinidae) in the southern Caribbean: are they really difference species?
Cervigón, F. and Alcalá, A. 1999. Los peces marinos de Venezuela. Vol. 5. Tiburones y Rayas. Fundación Museo del Mar.
Fechhelm, J.D. and McEacharn, J.D. 1984. A revision of the electric ray genus Diplobatis with notes on the interrelationships of Narcinidae (Chondrichthyes, Torpediniformes). Bulletin of the Florida State Museum 29(5): 171–209.
IUCN. 2006. IUCN Red List of Threatened Species.
IUCN SSC Shark Specialist Group. Specialist Group website. Available at: http://www.iucnssg.org/.
McEachran, J.D. and de Carvalho, M.R. 2002. Batoid fishes. In: K.E. Carpenter (ed). The Living Marine Resources of the Western Central Atlantic. Volume 1. Introduction, molluscs, crustaceans, hagfishes, sharks, batoid fishes and chimaeras. pp: 508–589. FAO Species Identification Guides for Fishery Purposes. FAO, Rome.
Medina, J.A. 2002. Ensamblajes de peces demersales explotados por la flota industrial camaronera en la plataforma continental de La Guajira (Caribe colombiano). Tesis pregrado Biólogo Marino. Universidad Jorge Tadeo Lozano, Facultad de Biología Marina. Santa Marta, 2002.
Valdez, J. and Aguilera, O. 1987. Los peces del Golfo de Venezuela. Fondo editorial CONICIT, Caracas.
|Citation:||Caldas, J.P., de Carvalho, M.R. & McCord, M.E. 2006. Diplobatis guamachensis. The IUCN Red List of Threatened Species 2006: e.T61402A12471427.Downloaded on 23 October 2017.|