Now showing items 1-4 of 4

    • Article

      From triphenyltins to integrated management of the 'pest' snail Cerithidea cingulata in mangrove-derived milkfish ponds in the Philippines 

      T Bagarinao & I Lantin-Olaguer - Hydrobiologia, 2000 - Kluwer Academic Publishers
      The potamidid snail Cerithidea cingulata is considered a pest in brackishwater milkfish ponds in the Philippines and has been controlled by the triphenyltin (TPT) compounds Aquatin and Brestan. But TPT is also toxic to other invertebrates, fishes, algae, bacteria and people, and high TPT residues occur in sea foods including milkfish. Thus, control of snails in milkfish ponds should be shifted from reliance on TPT to an integrated pest management (IPM) strategy. To formulate a responsible IPM, studies were conducted on C. cingulata in ponds and mangroves and the available data were synthesized with the relevant information from the literature. The deposit-feeding C. cingulata is a native resident of mangrove areas and becomes a problem in mangrove-derived ponds where the lack of competitors and predators results in 'ecological release' and population explosion. Snail densities ranged 1–470 m−2 in the mangroves and 100–5000 m−2 in ponds. In ponds, snails ranged 2–40 mm in shell length; those 25 mm long and 8 mm wide weighed 1 g on average, and had 150 mg flesh. Snails matured at 20 mm long and reproduced the whole year with a peak in Mar–Sep at water temperatures of 24–36 °C. Enriched sediments and stagnant water in ponds allowed fast growth and reproduction, low dispersal and high recruitment of snails. Snails were very tolerant to hypoxia and adverse conditions, but were killed within a week by sun-drying or by salinities of 48–70‰ and within 3 d by ammonium phosphate at 10 g l−1 or urea at 5 g l−1. IPM of snails requires changes in mind sets and perspectives of milkfish farmers and industry supporters and changes in farm practices and management. Snails must be viewed as a resource from which income can be made and employment can be generated. Harvest of snails for shellcraft and other enterprises also effectively removes the spawning population. Complete draining and sun-drying of ponds after harvest kills the adult snails and the egg strings on the bottom. Snails in puddles in the ponds may be killed by the usual nitrogen fertilizers and lime applied during pond preparation. Water input may be timed with periods of low veliger counts in the supply water. These IPM recommendations have yet to be verified.
    • Article

      Gonadal maturation, fecundity, spawning and timing of reproduction in the mud snail, Cerithidea cingulata, a pest in milkfish ponds in the Philippines 

      I Lantin-Olaguer & TU Bagarinao - Invertebrate Reproduction and Development, 2001 - Taylor & Francis
      Gonadal maturation, spawning, fecundity and timing of reproduction of the snail Cerithidea cingulata in a brackish water pond in Molo, Iloilo, Philippines, are described. Snails 4–41 mm in shell length were sampled monthly from May 1997 to May 1998; 25% were <25 mm, 67% were 20–30 mm, and 8% were >30 mm. The sexes are separate and could first be distinguished at 15 mm. Males are aphallic, have narrower shells than females of the same length, and have bright yellow-orange testes overlying the digestive gland deep inside the shell. Females have more robust shells, an ovipositor at the right side of the foot, and yellow-green ovaries overlying the digestive gland. The sex ratio was one male to two females in the pond population studied. Gonadal maturation was monitored by means of gonadosomatic index (GSI, gonad weight as a percent of visceral weight); maturation stages were based on the gonad appearance (immature, developing, mature) and histology (immature, developing, mature, redeveloping). GSI increased with snail size, and reached 16% in a 33-mm female. The smallest mature males and females were 18–19 mm, and most snails >20 mm were mature, spawning, or redeveloping. Histological sections showed all stages of gametogenesis in mature male snails. The oocyte size-frequency distributions in mature females showed mostly mature oocytes and secondary oocytes, but also oogonia and primary oocytes. GSI and the frequency of snails at different maturation stages varied over the year. Both GSI and the frequency of mature snails were highest during the summer months, April to August. Nevertheless, mature snails occurred throughout the whole year, as did mating and egg-laying. Fecundity (= number of oocytes >70 pμ) increased with size in mature females 2041 mm; an average 25-mm female produced about 1,500 oocytes and larger females produced a maximum of about 2,500 oocytes. Eggs strings laid on the pond bottom were 45–75 mm long; an average 64-mm string contained 2,000 eggs 210+20 pm in diameter. The density of eggs strings was highest (80–120/m2) during March-September. Eggs hatched after 6–7 d into planktonic veligers, which in turn settle on the pond bottom 11–12 d later as juveniles. Juveniles 2–6-mm long were most abundant in the pond during August-October.
    • Article

      Seasonal changes and coliform load of Jalaur river, province of Iloilo, Panay island, Philippines 

      I Lantin-Olaguer, SA Pedrajas-Mendoza, R Pakingking & A Yamamoto - Silliman Journal, 2010 - Silliman University
      Determination of the presence/absence of coliforms as the pollution indicator bacteria, total coliform count (TCC) and fecal coliform counts specifically Echerichia coli were carried out on specific sampling points in Jalaur River namely: Banban Pequeño (upstream), Calinog, Moroboro, Dingle, Passi near Sugar Central Mill and National Power Corporation (NPC) (midstream), and Nabitasan, Leganes (downstream) during the wet and dry months. Samples were analyzed using a defined technology, the Colilert® method, and its accuracy was verified with the conventional method (APHA Standard Methods).

      Results showed that coliforms were present in all sampling sites. In Calinog, total coliform count (TCC) was high (900 x101 MPN/100 ml) in July. Increased coliform abundance was associated with high rainfall due to animal wastes that were carried by runoffs. In September, Passi, near NPC, TCC and E. coli counts were 640 x101 and 630 x 101 MPN/100 ml, respectively. Reduction in counts in January, February and March was observed. Sediments in Passi near Sugar Central Mill during milling time in February showed a high TCC of 116 x 104 MPN/100 ml which was attributed to reduced current and disturbance, and silty loam sediments texture that favored bacterial adsorption to sediments. Dingle site exhibited a domination of other coliforms over E. coli in January and March. In Leganes, highest TCC of 551 x 101 MPN/100 ml was obtained in September. Coliform loads varied by season which was influenced by the availability of the nutrients and tolerance range to physical and chemical factors in the environment. Variability of the resultant interaction can also be attributed to climate changes such as extreme weather events—El niño phenomenon and increased nutrient loadings during heavy rains hence, increased coliform concentration in the river. The presence of coliforms in Jalaur River is indicative of contamination that can be aggravated by climate changes and implies that a potential health risk associated with pathogens causing water-borne diseases is present.
    • Article

      The sulfide tolerance of milkfish and tilapia in relation to fish kills in farms and natural waters in the Philippines 

      T Bagarinao & I Lantin-Olaguer - Hydrobiologia, 1998 - Kluwer Academic Publisher
      Fish kills of milkfish Chanos chanos and tilapia Oreochromis spp. now occur frequently in brackish, marine, and freshwater farms (ponds, pens, and cages) in the Philippines. Aquafarms with high organic load, limited water exchange and circulation, no aeration, and high stocking and feeding rates can become oxygen-depleted and allow sulfide from the sediments to appear in the water column and poison free-swimming fish. The sulfide tolerance of 2-5 g milkfish and 5-8 g O. mossambicus was determined in 25-liter aquaria with flow-through sea water (100 ml min-1) at 26-30 °C and sulfide stock solutions pumped in at 1ml min-1. Total sulfide concentrations in the aquaria were measured by the methylene blue method and used in the regression against the probits of % survival. Four experiments showed that the two species have similar sulfide tolerance. In sea water of pH 8-8.5, about 163 ± 68 μM or 5.2 ± 2.2 mg l-1 total sulfide (mean ± 2 se) or 10 μM or 313 μg l-1 H2S was lethal to 50% of the fish in 4-8 h, and 61 ± 3 μM total sulfide or 4 μM H2S in 24-96 h (to convert all sulfide concentrations: 1 μM = 32 μg l-1). Earthen pond bottoms had 0-382 μM total dissolved sulfide (mean ± sd - 54 ± 79 μM, n - 76); a tenth of the samples had >200 μM. The water column may have such sulfide levels under hypoxic or anoxic conditions. To simulate some of the conditions during fish kills, 5-12 g milkfish were exposed to an abrupt increase in sulfide, alone or in combination with progressive respiratory hypoxia and decreasing pH. The tests were done in the same flow-through set-up but with sulfide pumped in at 25 ml min-1. The lethal concentration for 50% of the fish was 197 μM total sulfide or 12 μM H2S at 2 h, but 28-53 μM sulfide allowed fish to survive 6-10 h. Milkfish in aquaria with no aeration nor flow-through sea water died of respiratory hypoxia in 5-8 h when oxygen dropped from 6 to 1 mg l-1. Under respiratory hypoxia with 30-115 μM sulfide, the fish died in 2.5-4 h. Tests with low pH were done by pumping a weak sulfuric acid solution at 25 ml min-1 into aquaria with flow-through sea water such that the pH dropped from 8 to 4 in 5 h. Under these conditions, milkfish died in 7-9 h when the pH was 3.5. When 30-93 μM sulfide was pumped in with the acid, the fish died in 2-6 h when the pH was still 4.5-6.3. Thus, sulfide, hypoxia, and low pH are each toxic to milkfish at particular levels and aggravate each other's toxicity. Aquafarms must be well oxygenated to prevent sulfide toxicity and fish kills.