A report originally published in the TTFNC Quarterly Bulletin, by Amy Deacon and Ryan Mohammed.
The picturesque freshwater streams of the Arima valley are internationally famous as the subject of hundreds of scientific papers about guppy behaviour and evolution. However, the Freshwater Group for the 2013 BioBlitz was more interested in the huge variety of species which share the habitat – from larger guppy-eating fish like the sardines (Characins), to the microscopic rock-bound diatoms on which guppies graze.
Led by Amy Deacon, Ryan Mohammed and Erin Mangal, a full and enthusiastic team sampled seven sites all the way from Verdant Vale, including Simla, Temple Village and sites within the grounds of the AWNC itself. These sites included some deep pools as well as shallow riffles.
Using two-person hand seine nets we recorded a total of six species of fish, including the spectacular zangee (Synbranchus marmoratus) and an unusually large sardine (Astyanax bimaculatus). Fish pots were also used overnight with limited success due to the shallow depth of the river, but nonetheless yielded Trinidad’s two species of teta – ‘normal’, and ‘jumbie’ or ‘doctor’ teta (Hypostomus robini and Ancistrus maracasae). Despite doubling the total of last year’s Tucker valley snapshot, six species is certainly an underestimate of what are actually there. Notable absences included the cichlids, Crenicichla sp. and Andinoacara pulcher.
Thanks to help from afar from Odonata expert John Michalski in the form of an illustrated list, we were able to identify several species of dragonflies and damselflies relatively easily – some of the prettiest were spotted at the Simla cement ponds, including the beautiful turquoise Micrathyria atra.
Our efforts to sample Odonata extended to capturing some of the aquatic larvae as well, using a surber sampler. This piece of equipment also allowed us to catch and identify the larval stages of mayflies, caddisflies, stoneflies and various other bottom-dwelling macroinvertebrates. One crustacean species was confirmed - the manicou crab (Eudaniela garmani) and several aquatic gastropods including Pomacea glauca and Marisa cornuarietis.
Back at base camp on Sunday morning, children enjoyed taking part in our ‘colour in the guppy’ competition, and visitors could view fish in the display tanks. There were also some wriggling aquatic invertebrates to look at under the microscope and posters all about some of the streams’ smallest inhabitants - the diatoms. These are tiny photosynthetic creatures encased in intricate glass shells and are normally invisible to the naked eye. However, under the microscope it is possible to admire their beauty and diversity at close range. We identified at least six different species of diatoms in the Arima Valley waterways.
Once again, the Freshwater Group have revealed hidden secrets of Trinidad’s streams, opening peoples’ eyes to the weird and wonderful creatures that grow, swim and crawl alongside the fish…