Occurrence of the non-native blenny Omobranchus punctatus ( Valenciennes , 1836 ) ( Perciformes : Blenniidae ) in the Amazon coastal zone , Brazil

The muzzled blenny Omobranchus punctatus (Valenciennes, 1836) is native to the Indo-Pacific region. The species has been recorded at a number of locations in the southwestern Atlantic, including the Brazilian states of Bahia, Santa Catarina, and Rio de Janeiro. This fish was probably introduced accidentally in ship fouling, and poses a potential threat to the local ecosystem.


Introduction
Omobranchus punctatus (Valenciennes, 1836) (Perciformes: Blennidae) inhabits brackish coastal waters, primarily in benthic habitats, occupying cracks in rocks and mangroves (Ismail and Clayton 1990).The original geographic range of the species included parts of the Indian and Pacific oceans, between Japan and Australia, in the east, and the Persian Gulf, in the west (Golani 2004).Since the first record outside of its original range, in Trinidad and Tobago (Springer and Gomon 1975), the species has been found in a number of parts of the western Atlantic, from Panama and Venezuela to northern, eastern, and southern Brazil (Gerhardinger et al. 2006;Lasso-Alcalá et al. 2008;Freitas and Velastin 2010;Loebmann et al. 2010;Costa et al. 2011).Wonham et al. (2000) relate the invasion and dispersion success of the blennies and gobies into novel environments to the physiological and behavioral characteristics of these taxa, including their cryptic habits, occupation of refuges, and spawning in crevices.These fish also tolerate a wide range of salinity levels.Together, these attributes allow the fish to survive in harbors, where they use ship hulls as refuges and spawning grounds, and are taken up in ballast water, which often leads to them being released into new environments.
In the present note, the occurrence of O. punctatus is reported from tidal pools on the Amazon coast of northern Brazil, where it coexists with a number of native species.

Methods
Specimens of Omobranchus punctatus (Figure 1) were collected from tidal pools on the Algodoal-Maiandeua Island Environmental Protection Area (APA Algodoal-Maiandeua) in the municipality of Maracanã in the Brazilian state of Pará.The island is located at the mouth of the Maracanã and Marapanim estuaries, between the coordinates 00°35′0″-00°38′29″S and 47°31′54″-47°34′57″W (Figure 2).Specimens were collected in April, June, September, and November, 2008, and between January and April, 2010.The specimens were collected at low tide at Caixa D'Água and Princesa beaches, in tidal pools that forms in depressions within the intertidal zone using a hand-net with a 5 mm mesh.A sample of 16 specimens was analysed.
Specimens were identified at the Vertebrate Ecology and Zoology Laboratory of the Biological Sciences Institute of the Federal University of Pará (UFPA).Following the procedure established by Springer and Gomon (1975), the standard length, length of the pectoral and pelvic fins, head length and orbit   diameter were measured in triplicate using a 150-mm caliper with a precision of 0.1 mm, and the mean of the three values was used for analysis.The rays of the dorsal, pectoral, ventral, and anal fins were counted in each specimen.
Physical-chemical properties of the pools in which the specimens were found were measured (Table 1).

Results and discussion
In total, we sampled 16 specimens from 11 different tidal pools on Caixa d'Água and Princesa beaches.Standard length varied between 17.37 mm and 70.54 mm (mean ±SD = 44.69±16.25 mm).This mean value was similar to that recorded by Gerhardinger et al. (2006), with average length of 44.23 mm.The mean value found in this study was smaller than that reported by Loebmann et al. (2010), that they have collected species with average length of 86.00 mm.But neither of these two studies sampled specimens smaller than 25.00mm.The dorsal rays of the specimens presented between 32 and 35 rays (Table 2), while the anal fins had 22 to 24 rays.All the specimens presented small branchial apertures on each side of the head, above the upper extreme of the pectoral fin, head lacking cirri or crests, body elongated and flattened (Figure 1).
The O. punctatus specimens showed a coloration pattern typical of the species, characterized by: head with uniform dark brown tonality, and darker spots near the operculum; dorsal surface brown, with dark brown transverse stripes running to the vertical median region of the body; cream-colored ventral surface; base of the pectoral fin cream, rays uniformly unpigmented, appearing translucent; insertion of the dorsal fin dark brown, pigmentation of the rays of the anterior three-quarters of the fin fading distally, posterior quarter uniformly beige; insertion of the anal fin brown, with uniformly brown rays; brown spot in the region of the caudal peduncle; rays of the caudal fin light brown, becoming uniformly unpigmented and translucent apically.
Copp et al. ( 2005) defined non-native species as those which do or did not occur naturally within an area, and which reached this area through direct or indirect human action, intentional or not.The introduction of invasive species into native communities is almost always the result of human activities (Carlton 1985), such as aquaculture or shipping activities, where the discharge of ballast water or the fouling leads to the introduction of many species, including fish (Ferreira et al. 2008).And it is suggested ballast water and biofouling as the most important vectors of introduction of species in the Brazilian marine realm (Lopes et al. 2009;Ferreira et al. 2009).
O. punctatus has been introduced into areas outside its natural range mainly through the discharge of ballast water of ocean-going vessels or trough disposal of ship fouling (Gerhardinger et al. 2006;Golani 2004;Springer and Gomon 1975;Lasso-Alcalá et al. 2008).Loebmann et al. (2010) recorded O. punctatus in a number of different localities in northeastern Brazil, and concluded that the species may have dispersed naturally to some areas, where potential for the discharge of water ballast would be limited.Francis et al. (2004) concluded that the species Omobranchus anolius (Valenciennes, in Cuvier and Valenciennes, 1836) probably reached New Zealand in ballast water, given the biological characteristics of the species made natural dispersion virtually impossible.In Venezuela, Colombia, and Panama, O. punctatus has been recorded in areas adjacent to major ports, making dispersion through ballast water the most likely scenario (Lasso-Alcalá et al. 2008).However, there is increasing evidence that ship fouling may be at least as important as a vector.For example, Ferreira et al. (2006) identified 22 exotic species from a total of 118 benthic taxa collected in the region of Arraial do Cabo, on the southeastern Brazilian coast, in the fouling of Ilha Grande Bay, in Rio de Janeiro (Gerhardinger et al. 2006).
A trophic study in tidal pools on Maranhão Island, in Brazil (Júnior 2006;unpublished data), indicated that O. punctatus is a herbivore, which ranges out from its refuge to scrape algae from the rocks, thus competing with the native species Scartella cristata (Linnaeus, 1758) (Perciformes: Blenniidae) for space and dietary resources.
Omobranchus punctatus has now been recorded along much of the coast of Brazil (Figure 3, Table 3), although the gaps in the available data make it unclear whether a continuous population has been established, and to what extent natural dispersion is occurring.More specifically, the possible impacts of the introduction of O. punctatus on the fauna the APA Algodoal-Maiandeua have yet to be understood.

Figure 2 .
Figure 2. Location of the study site, Algodoal-Maiandeua Island in northeastern Pará (Brazil), where the specimens of Omobranchus punctatus were collected in tidal pools in 2008 and 2010.

Figure 3 .
Figure 3. Locations at which the nonnative blenny Omobranchus punctatus has been recorded on the Brazilian coast in published and unpublished reports, including the present study.

Table 1 .
Physical-chemical parameters of the water from the tidal pools in which the specimens of Omobranchus punctatus were collected onAlgodoal-Maiandeua Island in 2008 and 2010.

Table 2 .
Morphometric and meristic data for the specimens of Omobranchus punctatus collected on Algodoal-Maiandeua Island in the Brazilian state of Pará.The lengths of the head, and the pectoral and pelvic fins are expressed as a percentage of the standard length, and the orbit diameter as a percentage of the head length.

Table 3 .
Localities at which the non-native blenny Omobranchus punctatus has been recorded on the Brazilian coast in published and unpublished reports, including the present study in the Amazon region.Ship fouling is also suspected as the vector for the introduction of the non-native blenny Omobranchus punctatus into the Parnaíba Delta, northeastern Brazil(Loebmann et al.  2010), Babitonga Bay, in Santa Catarina, and