Effects of salinity and food on growth and survival rate of mangrove snail (\(\textit{Nerita balteata}\) Reeve, 1885) at the spat larvae stage

Mangrove snail (Nerita balteata) belongs to gastropoda species distributed in the coastal intertidal and offshore islands of Quang Ninh province. Although the artificial seeds production of this species have been successful but still having a bottle neck as a low survival rate in the process by veliger larvae are transformed into spat larvae stage. Experiments were conducted to determine effects of salinity and food on growth rate and survival rate of mangrove snail in the stage of spat larvae in Quang Ninh province. The results showed that the optimal salinity for growth and developtment of spat larvae was 25‰ that resulted in a absoluted growth rate of 16.5 ± 2.19 µm/day and survival rate of 26.5 ± 0.57% and significantly higher compared to other treatments. The diet of benthic microalgae (Navicula sp.) combined with formulated feed (AP0 and Frippak) were most suitable for the growth and development of mangrove snail at the spat larvae stage with absoluted growth rate of 25,7 ± 1,28 µm/day; Whereas the survival rate of larvae of 32,3 ± 2,52% was significantly higher than those in the other treatments.

Density and nutrient content of Terebralia pallustris mangrove snails in mangrove ecosystems in Pannikiang Island, Barru Regency, South Sulawesi

Mangrove snail, Terebralia palustris Linnnaeus 1967, was also found on Pannikiang Island, Barru Regency, South Sulawesi. This study aims to describe the fluctuation of T. palustris density in a year of observation. This research was conducted for ten months from August 2018 to July 2019. There were two research stations. Each station has a large plot measuring 10m x 10m and in it, five small plots are measuring 1m x 1m. Measurements of environmental parameters such as temperature, salinity, and pH were carried out in situ. This snail meat as much as 100gr also analyzed proximate. The proximate analysis of the snail shows that crude protein content is 18.73% so that the snail is very suitable to be used as a source of protein. The highest density is in July 2019 and the lowest density is in August 2018.

Analisis Pendapatan dan Pemasaran Pekebak Ikan (Pelet Keong Bakau Pakan Ikan) di Kota Langsa

Pellets are a source of energy intake made by humans with certain compositions needed according to an aquatic organism. The need for artificial feed (pellets) will greatly support the success of cultivation. A good pellet will produce fast fish growth so the production costs are not too high. Feed on a fish is not the same because it must be adapted to the type of commodity and its eating habits. Good food is a food that has high protein and is easily obtained. One of them is mangrove snails (T. telescopium). Kuala Langsa is a village located in the city of Langsa which is directly adjacent to the Malacca Strait so that in this area mangroves are found. The advantage of this pellet is that it is easy to find mangrove snail base material and its availability is abundant so that later the price will be cheaper with higher quality protein content compared to the pellets available on the market. The benefits of making this pellet are: (1). The creation of quality fish feed pellets, as an alternative to fish feed. (2). As an application of the science of fish feed from college, and (3). As an application of entrepreneurship science, to hone skills and soft skills entrepreneurs, so that they are ready to become independent entrepreneurs when they graduate. This pellet has a value of R / C ratio of 1.33, which means that every capital issued in the amount of Rp. 100.00 will get an income of Rp. 137.00. Thus, the fish pellet feed business is feasible to be developed.

Penggunaan Keong Bakau Telescopium sp (Gastropoda: Potamididae) dan Siput Bakau Cerithidea sp (Gastropoda: Potamididae) Sebagai Biofilter terhadap Limbah Budidaya Ikan Bandeng (Chanos chanos)

Mangrove snail Telescopium sp and Cerithidea sp are natural biofilter that able used to manage the changes in water quality caused by the culture sewage. This research aimed to analyze the utilization of Telescopium sp and Cerithidea sp as natural biofilter for re-improving water quality level from culture sewage in the laboratory scale. The outcome of this study was expected to be valuable information that mangrove gastropods not only as pests in mariculture ponds, but also able to use as natural biofilter in pond sewage management for recovering water quality level. This research was conducted from April to July 2016 in Hatchery and Aquaculture Technology Laboratory, Aquaculture Department, Agriculture Faculty, Malikussaleh University. Descriptive and quantitative methods used in this research including two treatment and three replications. Water quality such as turbidity, temperature, ammonia, nitrate, nitrite, orthophosphate, pH and dissolved oxygen measured periodically as research parameters. The result showed that the utilization of mangrove gastropod Telescopium sp and Cerithidea sp as natural biofilter was able to re-improving the water quality value such as pH, ammonia, nitrat, nitrit, orthophosphate and turbidity to the normal level. Meanwhile, the utilization of mangrove gastropods as natural biofilter does not gave any significant changes in the value of temperature, salinity and dissolved oxygen. Cerithidea sp also has better performance to reduce the water nutrient level in culture sewage compared than Telescopium sp. Keyword: mangrove gastropod, biofiltration, water quality, culture sewage

PEMANFAATAN KITOSAN CANGKANG KEONG BAKAU (Telescopium sp) SEBAGAI PENGIKAT ION LOGAM TIMBAL (Pb) DALAM LARUTAN

ABSTRACTResearch utilization of mangrove snail chitosan conech shell (Telescopium sp) as a binding metal ions of lead (Pb) in solution. This study aims to determine the best time of the metal ion absorption of lead (Pb) by a conch shell chitosan mangrove (Telescopium sp) with the remains of 150 rpm shaking method. This research was conducted by completely randomized design (CRD) and 4 variations of shaking time is 50, 55, 60 and 65 minutes. Each treatment was repeated three times. The results obtained are binding Pb (II) by the highest chitosan during 65 minutes agitation is 98.27%. Key words: Chitosan, absorption, lead