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Growth of giant tiger prawn, Penaeus monodonFabricius, under co-culture with a discarded filamentous seaweed, Chaetomorpha ligustica (Kü tzing) Kü tzing, at an aquarium-scale Isao Tsutsui AE Poonmanee Kanjanaworakul AE Prapansak Srisapoome AE Dusit Aue-umneoy AE Kaoru Hamano Abstract Growth of juvenile giant tiger prawn, Penaeus monodon Fabricius, was evaluated at an aquarium-scale in co-culture with a discarded filamentous seaweed, Chaetomorpha ligustica (Kützing) Kützing. Juveniles at different ages in days were examined, designated as J 16, J 44, J 58, J 93 and J 128, where a 1-day-old juvenile (J 1) is equivalent to a 20-day-old post-larva (PL 20)). Juveniles at every age group grazed directly on live C. ligustica, even those fed an artificial shrimp diet to satiation. Mean specific growth rate (SGR: % day -1 ) was higher in early age juveniles. Compared to mono-culture, significant differences in growth were observed at J 16 (4.44% day -1 ) and J 44 (1.60% day -1 ); however, no significant differences were recorded at J 58 (1.16% day -1 ), J 93 (0.75% day -1 ) or J 128 (0.45% day -1 ). It was concluded that co-culture of giant tiger prawn with C. ligustica has a dietary advantage, especially in early age juveniles. Age (days)J 16 J 44 J 58 J 93 J 128

Aims:  This study aimed at surveying prevalence of oxytetracycline (OTC)‐resistant bacteria in the white‐leg shrimp Litopenaeus vannamei, and the black tiger shrimp Penaeus monodon, intensively cultured in Thailand. We investigated the phylogenetic diversity of the bacterial isolates, as well as the minimum inhibitory concentration (MIC) of OTC, the occurrence of major OTC‐resistant genes and multiple‐antibiotic resistance in the isolates. Methods and Results:  Shrimps were collected from culture ponds, and the homogenates of whole bodies were plated on tryptic soy agar supplemented with or without OTC. Percentages of OTC‐resistant bacteria were 0·3–52·1% in white‐leg samples and 0·008–22·3% in black tiger samples. Analyses of 16S rDNA sequences indicated that most OTC‐resistant isolates were closely related to Aeromonas spp. and Lactococcus garvieae. MICs of OTC were 4–128 μg ml−1 in the OTC‐resistant aeromonads and 128–256 μg ml−1 in OTC‐resistant L. garvieae. OTC resistance was found to be conferred by the genes tet(A), tet(C), tet(D), tet(E), tet(M) and tet(S), detected either singly or in pairs. No resistance to ceftazidime, imipenem or chloramphenicol was observed in any isolate. Conclusions:  Both species of shrimp are associated with OTC‐resistant bacteria, occasionally at high densities exceeding 106 cfu g−1. The associated bacteria, predominantly Lactococcus and Aeromonas genera, are potential pathogens and are reservoirs of a variety of OTC‐resistant genes. Significance and Impact of the Study:  Cultured shrimps can be vehicle to carry OTC‐resistant bacteria to domestic and foreign consumers via the food chain. Very low populations of OTC‐resistant bacteria observed in the several ponds suggest that levels of the resistant bacteria are artificially high and should be reduced in farmed shrimps.

The effects of salinity and water temperature on growth and survival of Chaetomorpha sp., one of the green tidal filamentous algae, were investigated. Field surveys revealed that this alga was abundant throughout the year in stagnant coastal waters of central Thailand. Chaetomorpha sp. was found in salinities of 3.4-90.0 and water temperatures of 20.1-40.9°C. Chaetomorpha sp. biomass fluctuated between 9.2 and 162 kg dry weight in a saline swamp, without significant differences among seasons. The highest mean specific growth rate of approximately, 60 % day -1 was observed in laboratory experimental trials at salinities of 20-30 at 30°C. Salinity and water temperature significantly affected growth of this alga independently and interactively. Based on these results, Chaetomorpha sp. can easily grow, survive and monopolize in stagnant waters where the salinity and temperature greatly fluctuate because of their euryhaline and eurythermal nature as well as their high growth rate.