The effects of decomposing mangrove leaf litter and its tannins on the water quality, growth and survival of tiger prawn (Penaeus monodon) post-larvae

Sri Rejeki (Speaker), Marcel Middelians (Contributor), Lestari Lakhsmi Widowati (Contributor), Restiana Wisnu Ariyati (Contributor), Bosma, R. (Contributor)

Activity: Talk or presentation › Oral presentation

Description

Prawn farming in Demak, Indonesia is often practiced in silvo-aquaculture systems; mostly mangrove trees are planted on pond bunds. Mangrove leaves or its substrates may impact prawn. Mangrove regrowth in new habitats usually starts with Avicennia marina (AM) while planting is mostly done with Rhizophora
apiculata (RA). We compared the effects of decomposing fresh leaves of AM and
RA, on water quality and performance of Penaeus monodon post larvae (PL).
Hundred PL21 (0.28 g) were stocked in each of 33 aerated tanks, with 800L
brackish water, assigned to triplicates of six concentrations (g/L) of both species
leaves: 0 (control), 0.125, 0.25, 0.5, 0.125 minced leave and 0.125 leachate of
minced leaves. The PL were fed 3x daily with pellets at 10% of initial total body
weight. Temperature, salinity, DO and pH were recorded daily. Tannin, H2S and
NH3-N concentrations were measured every ten days. After 37 days, prawn's body weights (BW) were measured, and specific growth rate (SGR, %/day) and survival rates (SR, %) calculated. Results were analysed with ANOVA and Pearson's
correlation. Leaf concentrations had no effect on DO, H2S, non-significantly
effected pH and SR, but significantly effected tannin, NH3-N and SGR. SR varied
from 62±14 to 70±8, and SGR between 1.5 to 2.1. The correlation of BW with SR
for both AM and RA was highly significantly negative (-0.7), thus obscuring potential effects of tannin, NH3-N, and species. As feeding levels were not adjusted, prawn probably fed on both dead and molting prawn. Tannin concentrations in the water fluctuated around 2 mg/L, while in green leaves of RA and AM these were 2.2 ±0.9 and 1.6 ±0.4, respectively. NH3-N increased from 0.67 to levels up to 0.99 mg/L making decomposing mangrove leaves of AM and RA toxic for prawn in tanks without water exchange.

Period	8 Apr 2019 → 12 Apr 2019
Event title	12th Asian Fisheries & Aquaculture Forum (AFAF): Transforming Asian Fisheries and Aquaculture for Sustainable Production and Nutrition
Event type	Conference
Location	Iloilo, Philippines