Juvenile morphology and occurrence patterns of three Butis species (Gobioidei: Eleotridae) in a mangrove estuary, southern Thailand

Abstract

Juveniles of three eleotrid Butis species (B. butis, B. humeralis, and B. koilomatodon) are described; their occurrence patterns were examined in Sikao Creek, a mangrove estuary located in southern Thailand. Juveniles of each species were distinguished by the following characters: B. butis with no bands on body and pale pelvic fins; B. humeralis with no bands on body and densely pigmented pelvic fins; and B. koilomatodon with 5-6 regular bands on body and a fleshy process (preorbital knob) on the snout. Although B. butis shared the aforementioned characters with B. amboinensis found in the same estuary, the former was distinguished from the latter by having a greater number of pectoral fin rays (18-21 vs. 17) and a deeper caudal peduncle. Distribution patterns of the three Butis species in Sikao Creek were distinguishable from each other. Smaller B. butis [mean ± SD = 22.7 ± 16.9 mm in standard length (SL), n = 32] occurred in the upper reach of the estuary, while larger specimens (52.4 ± 26.2 mm SL, n = 18 and 51.5 ± 29.7 mm SL, n = 10, respectively) were found in the middle and lower reaches and none in the marine area. In B. humeralis and B. koilomatodon, only juveniles were caught except for one adult specimen each. Juveniles (8.9-16.5 mm SL, n = 79) of B. humeralis occurred in the upper and middle reaches and the marine area. B. koilomatodon juveniles (9.9-13.7 mm SL, n = 30) were distributed in all areas from the lower to upper reaches.

Morphological characters and occurrence patterns of juveniles of two estuarine gobies, Acentrogobius kranjiensis and Acentrogobius malayanus, verified by molecular identification

“…These results suggested that juveniles of both Acentrogobius species migrate with growth between estuarine habitats, although migration patterns differ between the species. Recently, similar post‐settlement movement data from within mangrove estuaries has been reported for three Eleotris species (Maeda & Tachihara, 2005) and three Butis species (Yokoo et al , 2006). Such movement may play important roles in reducing competition between species, thereby structuring the fish assemblage with greater species richness.…”

“…Acentrogobius kranjiensis and A. malayanus occurred during both the rainy and dry seasons, although individual numbers were much higher in the former, indicating that the main spawning season was during that time. Greater abundances of juveniles in the rainy season have been well documented for fish assemblages in tropical mangrove estuaries (Robertson & Duke, 1987;Laegdsgaard & Johnson, 1995;Blaber, 2000;Ikejima et al, 2003;Yokoo et al, 2006).…”

“…Mangrove estuaries around the world are recognized as important nursery grounds for a number of fish species (Robertson & Duke, 1987; Chong et al , 1990; Laegdsgaard & Johnson, 1995), including gobioids, the most dominant group in Indo‐Pacific mangrove estuaries (Collette, 1983; Robertson & Duke, 1987; Blaber & Milton, 1990) and, due to their species diversity and abundance, critical components of estuarine ecosystems. Although the larval and juvenile ecology of some gobioid species have been well studied (Maeda & Tachihara, 2005; Yokoo et al , 2006), early life‐history data are scarce for the majority of gobioids, often due to problems in the identification of larval and juvenile forms.…”

Seasonal dynamics of the juvenile fish community structure in the Maowei Sea mangroves

“…It should be noted that the two dominant species, Pseudogobius javanicus and Omobranchus elegans (together representing 81.68% of the catch), are both demersal species that probably spend their entire life cycles within the estuary [ 29 , 30 ]. Hence, it is rather likely that persistent sampling six to ten times monthly throughout the entire year in the same mangrove channel have resulted in notably reduced numbers of these two species on the sampled locality.…”

Geographic expansion of the invasive mud sleeper Butis koilomatodon (Perciformes: Eleotridae) in the western Atlantic Ocean

“…The head has narrow dark‐brown bands between the anteroventral edge of the eye and the middle of the upper lip. This species is distinguished from its congeners by four to seven regular bands on the body and a serrated process (preorbital knob) on the snout (Yokoo et al , 2006; Vreven et al , 2007). Most specimens were caught on the mud bottom of estuaries, but the two from the Rio Escuro were found among algae attached to mangrove roots.…”