A Survey of Freshwater Fish Distribution in Tobago, West Indies Ryan S. Mohammed, Karl Phillips, Kerresha Khan and Avi Bhagan Mohammed, R.S., Phillips, K., Khan, K., and Bhagan, A. 2015. A Survey of Freshwater Fish Distribution in Tobago, West Indies. Living World, Journal of The Trinidad and Tobago Field Naturalists’ Club , 2015, 44-51. $6XUYH\RI)UHVKZDWHU)LVK'LVWULEXWLRQLQ7REDJR:HVW,QGLHV Ryan S. Mohammed1, 4*, Karl Phillips2, Kerresha Khan1 and Avi Bhagan3 1. Department of Life Sciences, Faculty of Science and Technology, The University of the West Indies, St. Augustine, Trinidad, Republic of Trinidad and Tobago. 2. /DERUDWRU\RI(YROXWLRQDU\%LRORJ\'HSDUWPHQWRI%LRORJ\$GDP0LFNLHZLF]8QLYHUVLW\3R]QDĔ3RODQG Department of Geomatics Engineering and Land Management, Faculty of Engineering, University of the West Indies, St. Augustine, Trinidad, Republic of Trinidad and Tobago. 4. Environmental Research Institute of Charlotteville (ERIC), Tobago, Republic of Trinidad and Tobago. *corresponding author: [email protected] ABSTRACT 7KHIUHVKZDWHU¿VKRI7REDJRZHUHUHSRUWHGE\DQXPEHURIUHVHDUFKHUVEHWZHHQDQGZLWKGLIIHULQJVSHFLHV ULFKQHVVDQGGLYHUVLW\EHLQJOLVWHGE\HDFK5HVXOWVRIWKHUHFHQWVXUYH\UHSRUWHGKHUHVHUYHWRXSGDWHWKLVEDVHOLQH Surveys were conducted at 81 sites in Tobago over the time period 2004-2015, with observations being conducted both nocturnally and diurnally. The most widespread species was Sicydium punctatum (Gobiidae). The species with the highest abundance was Poecilia reticulata (Poeciliidae), and the rarest species was Gobiesox nudus (Gobiesocidae). Micropoecilia picta (Poeciliidae), Ctenogobius boleosoma (Gobiidae), and Synbranchus marmoratus (Synbranchidae) were documented IRUWKH¿UVWWLPHIRU7REDJR7KHLFKWK\RIDXQDOULFKQHVVIRUWKLVVXUYH\QRZVWDQGVDWVSHFLHV7KHGUDLQDJHZLWKWKH JUHDWHVWVSHFLHVULFKQHVVZDV5R[ERURXJK5LYHUZLWKQLQHVSHFLHVQRWHG Key words: 7REDJR¿VKIUHVKZDWHUGLVWULEXWLRQVXUYH\7ULQLGDGDQG7REDJR INTRODUCTION DUHLGHDOKDELWDWVIRUPLJUDWRU\VSHFLHVRI¿VKDQGVXFK 7KHIUHVKZDWHU¿VKDVVHPEODJHVRI7ULQLGDGDQG7R- habitats should be investigated and their ichthyofauna bago have been described previously by several authors documented in dedicated surveys. LQFOXGLQJ.HQQ\ 3KLOOLS 3KLOOLSDQG 7KHQDWXUHRIIUHVKZDWHU¿VKVDPSOLQJPHDQVWKDWWKHUH Ramnarine (2001), Mohammed et al. (2010), and most can be considerable heterogeneity over space and time recently by Phillip et al. *XSS\ OLVWHGRQO\ and imperfect sampling, especially for rare species. New WZRVSHFLHVIURP7REDJRZKLOVW3KLOOLS OLVWHG species may be added to the list by means of increased species. Most authors have focussed their attention on sampling effort and increased number of sites sampled. Trinidad; here we focus on Tobago’s freshwater ichthyo- 3UHYLRXVGDWDVHWVRI¿VKGLVWULEXWLRQRQ7REDJRDUHGDW- faunal distribution. HGZLWK3KLOOLS EHLQJWKHPRVWUHFHQWVWXG\7KH Tobago can be considered as the last outpost of the purpose of our account is to provide an updated baseline Andean chain, at the edge of the South American continen- GLVWULEXWLRQIRUIXWXUHVWXGLHVUDWKHUWKDQDGH¿QLWLYHDF- tal shelf and separated from the Lesser Antilles by many count of which species are present on Tobago. NLORPHWUHVRIGHHSZDWHUV +DUG\ $VDUHVXOWWKH ÀRUDDQGIDXQDRI7REDJRLVW\SLFDORIFRQWLQHQWDO6RXWK METHODOLOGY America, yet it differs from that of Trinidad in being rather Between 2004 and 2015, several freshwater sites in depauperate, as is typical of small islands, with a distinct Tobago were visited by parties that varied from 1 to 4 :HVW,QGLDQLQÀXHQFH7ULQLGDGKDVDFRORQLVLQJ]RQHZLWK persons including R.S. Mohammed and K. Phillips. These D6RXWK$PHULFDQLQÀXHQFH .HQQ\ DVDUHVXOWRI ZHUHGRQHUHSHDWHGO\IRUVFLHQWL¿FREVHUYDWLRQVRUHFR- low salinities in the Columbus Channel, coastal near shores ORJLFDOHYDOXDWLRQV7KHVHVLWHVLQFOXGHGULYHUVDUWL¿FLDO of the Atlantic and heavy Orinoco River discharge. Tobago, water channels, and ponds. Surveys were conducted both however, does not seem to possess such a region. Kenny QRFWXUQDOO\DQGGLXUQDOO\$WRWDORIVLWHVZHUHYLVLWHG (Ibid.) noted that the major oceanic currents near Toba- DWOHDVWDQQXDOO\&RQ¿UPHGGHWHFWLRQRI¿VKVSHFLHVLV JRDUHLQÀXHQFHGE\WKH2ULQRFR5LYHUDQGWKH$WODQWLF UHSRUWHGKHUHSHUVLWH )LJ ,GHQWL¿FDWLRQVZHUHFRQ- 2FHDQDQGFRPHIURPDVRXWKHDVWHUQGLUHFWLRQÀRZLQJLQ ¿UPHGE\XVHRIWD[RQRPLFNH\VLQ3KLOOLSet al. a northwest direction. Coupled with a steep coastal topog- where necessary. raphy, colonisation of Tobago’s estuaries and watercourses We restrict our review herein to true freshwater species E\6RXWK$PHULFDQRU7ULQLGDGLDQIUHVKZDWHU¿VKZRXOG (outlined by Phillip et al. DQGLQWHQWLRQDOO\RPLW seem very unlikely. However, brackish estuarine regions estuarine species. Our account is also void of distributions 44 Survey of Freshwater Fish Distribution in Tobago 45 on Little Tobago and all other islands near Tobago, since species reported and had the highest ichthyofaunal species these do not have permanent water channels. richness. Seining was done by use of two-person seines (1.0m 7KHIROORZLQJPDSV )LJV VKRZVSHFLHVGLVWULEX- and 5.0m) of mesh size 0.5cm and additionally by use of WLRQVDVZHOODVFRPSDULVRQVWRGDWDIURP3KLOOLS a single-person seine (1.0m) with a mesh size of <0.1cm. Table 1 provides GPS coordinates (UTM 20P) for all sites Cast netting with a 2.0m diameter (1.0cm mesh) was con- sampled. Most sightings of Agonostomus monticola were GXFWHG)LVKSRWV [[FPZLWKDPHVKVL]H made on the periphery of the island along the southeastern, of 0.5cm) were used for overnight trapping at some sites northeastern, and northwestern coasts, similar to the dis- where vegetation and water depth allowed. These methods WULEXWLRQVQRWHGE\3KLOOLS )LJ Anablepsoides were not standardised for all sites visited but were adjusted hartii had sparse distributions across the island but was to suit each particular site, depending upon variability of the only species that ventured across the Main Ridge and substrate, riparian vegetation, and elevation. In addition, breached elevation barriers at several short waterfalls accessibility to sites was considered when transporting and )LJ Awaous banana was detected on both the north deploying sampling gear. All specimens from sampling DQGVRXWKFRDVWVSUHYLRXVO\3KLOOLS KDGQRWHGLWV HIIRUWVZHUHUHOHDVHGLPPHGLDWHO\DIWHULGHQWL¿FDWLRQDW distribution only on the south coast (Fig. 4). The Ctenogo- the site where collected. bius boleosomaVLJKWLQJVUHSUHVHQWWKH¿UVWUHSRUWRIWKLV species for Tobago. The species is localised along east and northeast coast regions (Fig. 5). Sicydium punctatum was IRXQGDWRIWKHVLWHVJLYLQJLWWKHZLGHVWGLVWULEX- tion on the island; as did Anablepsoides hartii, it has also conquered elevation barriers of the Main Ridge (Fig. 6). Gobiesox nudus is the rarest species on the island, only IRXQGLQWKHQRUWKHUQGUDLQDJHV3UHYLRXVO\3KLOOLS had noted it at multiple sites in the northeast; however, our data expand its distribution to additional drainages, mostly DORQJWKHQRUWKHUQFRDVW )LJ Gobiomorus dormitor has a wide distribution and has ventured into the interior of the island, conquering some of the elevation barriers )LJ Eleotris pisonis is the second rarest species on the island. It can be found in all coastal rivers but has a sparse GLVWULEXWLRQ3KLOOLS IRXQGLWRQERWKQRUWKDQGVRXWK coastlines; our data expanded its distribution to additional Fig. 1.1HZDQGSUHYLRXV 3KLOOLS VDPSOHVLWHV VLWHVRQGUDLQDJHVRIWKHÀDWZDWHUVWUHWFKHVEHORZWKHODVW ULIÀHWRZDUGVWKHFRDVWOLQH )LJ Synbranchus mar- RESULTS moratus was found only in the central eastern drainages; 2XUVXUYH\\LHOGHGQLQHIDPLOLHVDQGVSHFLHVRI RXUGHWHFWLRQFRQVWLWXWHVWKH¿UVWRI¿FLDOFRQ¿UPDWLRQRI IUHVKZDWHU¿VKWZRPHPEHUVRIWKH3RHFLOLLGDHPoecilia the species in Tobago (Fig. 10). Poecilia reticulata has a reticulata and Micropoecilia picta; one member of the predominantly southeast to northeast distribution and is Rivulidae - Anablepsoides hartii (formerly Rivulus hartii); WKHPRVWDEXQGDQWIUHVKZDWHU¿VKVSHFLHVLQ7REDJR )LJ three members of the Gobiidae - Awaous banana, Ctenogo- 11). Micropoecilia picta has a distribution similar to that of bius boleosoma and Sicydium punctatum; two members of P. reticulata. Micropoecilia picta had sparse localised de- the Eleotridae - Eleotris pisonis and Gobiomorus dormitor; tections in the southern and northeastern regions; although one member of the Gobiesocidae - Gobiesox nudus; one regarded as a freshwater species, it has a wide tolerance member of the Synbranchidae - Synbranchus marmoratus; for brackish systems. Mixed shoals of P. reticulata and M. one member of the Mugilidae - Agonostomus monticola; picta were seen at Site 22 and on the Richmond, Lois D’or, one member of the Anguillidae - Anguilla rostrata; and Roxborough, Argyle, Goldborough, and Delaford Rivers one member of the Cichlidae - Oreochromis mossambicus. (Fig. 12). However, the rare red male morph was noted Sicydium punctatum was the most widespread species. at King’s Bay, Bon Accord, Buccoo and Richmond. This It had the most even distribution across the island, being morph has only been documented in males on the South IRXQGDWRIVLWHVIROORZHGFORVHO\E\Agonostomus American mainland (Lindholm et al. 2015). Oreochromis monticola RIVLWHV +RZHYHUWKHJXSS\Poecilia mossambicus is localised to southern Tobago and has an reticulata, had the highest densities and abundances (pers. isolated population at the Hillsborough Dam (Site 56) (G. obs.). The Roxborough River supported nine of the 12 :KLWHSHUVFRPP )LJ richness isalsogivenpersite. 1. Table 46 Anguillidae CichlidaeEleotridae GobiesocidaeGobiidae MugilidaePoeciliidae Rivulidae Synbranchidae Site Species 0indicatesnon-detection;1presence.Ichthyofaunalspecies