Crypsis
Juvenile T. niloticus are highly cryptic due to their size, colouring and protective coral rubble environment they live in (Caste, Naviti and Nguyen, 1996).
This cryptic nature makes experiments and programs requiring a mark and recapture element more difficult, as juveniles are not recaptured simply because they are overlooked (Pakoa, Friedman and Damlamian, 2010). It makes the survival estimates of juveniles tough to quantify (Caste, Naviti and Nguyen, 1996).
Caste, Naviti and Nguyen (1996) conducted and experiment to measure the effect of crypsis on the recapture of T. niloticus. 2- 3 days after releasing T. niloticus to the wild they sought to recapture their specimens. Half of the animals were "flagged" with bright tape to make them easily identifiable, while half of them were not. Unsurprisingly on Orpheus Island, off Australia, 76% of the "flagged" animals were recaptured, and only 52% of the unflagged. Scientists need to take this element into consideration when discussing the success of their findings concerning the organism.
Adult specimens can easily be seen through the water column, and are easy to identify (Nash, 1985). The difference between the adults and juveniles is primarily due to the size of the adults, as well as the micro- habitat they live in.
The photo below shows an adult T. niloticus on the Heron Island reef flat in 2011. It is approximately 7cm across the base and easily identifiable.
 |