Wansuk Senanan

Spawning-Site and Natal-Site Fidelity by Northern Pike in a Large Lake: Mark–Recapture and Genetic Evidence

Abstract We supplemented physical-tagging data with genetic data to provide evidence for spawning-site and natal-site fidelity by two spawning populations of northern pike Esox lucius in Kabetogama Lake, Minnesota. A mark–recapture study supported previous reports that individual northern pike and other esocids tend to return to the spawning grounds that they used in previous years. Of 1,900 northern pike marked at two spawning sites in the first year of the study, 23% were recaptured on spawning grounds one to three times over the next 4 years. Of these recaptured fish, only 1.3% and 4.8%, respectively, of those marked at the two spawning sites were recaptured at the other site. Tag returns from anglers showed that the year-round ranges for fish from the two sites overlapped, so that lack of dispersal could not completely explain the high fidelity to spawning sites. Significant allele frequency differences at five microsatellite DNA loci between the 1983 (P = 0.03) and 1985 (P = 0.002) spawning populatio...

A Review of Northern Pike Population Genetics Research andIts Implications for Management

Abstract Conserving genetic diversity within and among populations of northern pike Esox lucius is important for maintaining their short-term fitness and long-term evolutionary potential. Northern pike have consistently shown low within-population variation, as detected by allozymes, mitochondrial DNA, and randomly amplified polymorphic DNA. Microsatellite DNA loci reveal considerably greater variation in northern pike, yet microsatellite variation tends to be less than that in other fish species. Low genetic variation within populations may result from compounding factors of low effective population size and bottlenecks. Allozyme, randomly amplified polymorphic DNA, and microsatellite markers have revealed significant differentiation of populations located in different continents and major drainages, but only microsatellites have differentiated populations on finer geographic scales. Within the north-central United States, analyses with microsatellites have detected genetic differences among most populat...

THE PRESENCE OF THE PACIFIC WHITELEG SHRIMP (LITOPENAEUS VANNAMEI, BOONE, 1931) IN THE WILD IN THAILAND

Abstract Pacific whiteleg shrimp (Litopenaeus vannamei, Boone, 1931) was first introduced to Thailand for aquaculture in the late 1990s as an alternative to a native shrimp species, black tiger prawn (Penaeus monodon, Fabricius, 1798). We documented the presence of L. vannamei in the Bangpakong river system, an important watershed in eastern Thailand with a high density of shrimp farms. This paper is a part of a larger study to evaluate potential ecological consequences of introduced L. vannamei. During January–November 2005 (three sampling periods), we sampled wild marine shrimp with commercial shrimp nets (6 m wide × 5 m deep × 25 m long with 2.5 cm mesh) at four sites within the Bangpakong estuary. Results indicated that L. vannamei were present at least once at all sampling sites during the study. Proportion of L. vannamei relative to all Penaeid shrimp per net in the Bangpakong estuary was 0.005 ± 0.0016 (January–March 2005), 0.0005 ± 0.00021 (June 2005), and 0.061 ± 0.0035 (September–November 2005). Litopenaeus vannamei were present in 30%, 16% and 100% of nets used for the three consecutive sampling periods. The mean sizes of L. vannamei captured were 22.4 ± 0.75, 25.1 ± 0.07, and 22.0 ± 0.29 mm postorbital carapace length (PO-CL) and 85.6 ± 2.66, 105.5 ± 6.13, and 85.8 ± 1.04 mm body length. The CL and body sizes were significantly larger in samples collected in June 2005 than the two other periods. Increasing frequencies of occurrence of L. vannamei in the Bangpakong estuary call for the determination of sources (escapes versus a self-sustaining population) and mitigation.

HEAVY METALS IN WILD BANANA PRAWN (FENNEROPENAEUS MERGUIENSIS DE MAN, 1888) FROM CHANTABURI AND TRAT PROVINCES, THAILAND

Abstract Concentrations of the heavy metals cadmium (Cd), mercury (Hg), nickel (Ni), lead (Pb), chromium (Cr), copper (Cu) and zinc (Zn) in adult banana prawns (Fenneropenaeus merguiensis de Man, 1888) were determined. Banana prawn samples were collected from two provinces of Thailand (Ampur LamSing, Chantaburi, and Ban Huanumkao, Trat) by gill net. Twenty five prawns from each province were randomly chosen from the catch and each prawn sample was divided into two parts: cephalothorax and abdominal muscle. Both parts were digested with concentrated nitric acid and hydrogen peroxide under pressure in a microwave digester. Hg levels were determined using a Cold Vapor Atomic Fluorescence Spectrometer. Cd, Cu, Cr, Ni, Pb, and Zn concentrations were determined using Atomic Absorption Spectrophotometer. Trace concentrations of Cd, Cu, Cr, Ni, Pb, and Zn in cephalothorax of banana prawns from both provinces were significantly higher (P < 0.05) than in muscle, with no significant difference observed for Hg. Concentrations of Hg, Cu, Zn, and Cd in banana prawns from Chantaburi province were significantly higher (P < 0.05) than those from Trat province. There was no significant difference observed between the contents of Pb, Ni, and Cr in banana prawns caught from the two provinces. Heavy metal content in banana prawn, especially in cephalothorax tissue, may be a good indicator (sentinel organism) of heavy metal contamination in the coastal environment. Mean concentrations of all heavy metals in abdominal muscle (edible part) were within the safety limits for human consumption. However, Cd and Cu concentrations in some of the cephalothorax samples from Chantaburi province were higher than the safety limits for human consumption. This suggests that a close monitoring program is needed to ensure the safety of F. merguiensis as a food source.

SPECIES AND DISTRIBUTION OF PENAEOID SHRIMPS IN THAILAND

Abstract Species and distribution of Penaeoid shrimps in Thailand were studied in specimens of shrimp collected from fish markets and fishing ports of 23 provinces along the Gulf of Thailand and the Andaman Sea coast. Identification of species was based on the morphological characters of rostrum, carapace, branchiae, antennule, antenna, third maxilliped, pereiopods, pleopods, abdomen, telson, petasma, thelycum, and the colored pattern of the whole body based on keys and diagnoses available from the current literature. A total of 50 species from 13 genera and 3 families of Penaeoidea were identified in coastal provinces of the Gulf of Thailand and the Andaman Sea. Additional research is needed to more clearly define the distribution of shrimp species in the Gulf of Thailand and the Andaman Sea coasts.

Effects of landscape features on population genetic variation of a tropical stream fish, Stone lapping minnow, Garra cambodgiensis, in the upper Nan River drainage basin, northern Thailand

Spatial genetic variation of river-dwelling freshwater fishes is typically affected by the historical and contemporary river landscape as well as life-history traits. Tropical river and stream landscapes have endured extended geological change, shaping the existing pattern of genetic diversity, but were not directly affected by glaciation. Thus, spatial genetic variation of tropical fish populations should look very different from the pattern observed in temperate fish populations. These data are becoming important for designing appropriate management and conservation plans, as these aquatic systems are undergoing intense development and exploitation. This study evaluated the effects of landscape features on population genetic diversity of Garra cambodgiensis, a stream cyprinid, in eight tributary streams in the upper Nan River drainage basin (n = 30–100 individuals/location), Nan Province, Thailand. These populations are under intense fishing pressure from local communities. Based on 11 microsatellite loci, we detected moderate genetic diversity within eight population samples (average number of alleles per locus = 10.99 ± 3.00; allelic richness = 10.12 ± 2.44). Allelic richness within samples and stream order of the sampling location were negatively correlated (P < 0.05). We did not detect recent bottleneck events in these populations, but we did detect genetic divergence among populations (Global FST = 0.022, P < 0.01). The Bayesian clustering algorithms (TESS and STRUCTURE) suggested that four to five genetic clusters roughly coincide with sub-basins: (1) headwater streams/main stem of the Nan River, (2) a middle tributary, (3) a southeastern tributary and (4) a southwestern tributary. We observed positive correlation between geographic distance and linearized FST (P < 0.05), and the genetic differentiation pattern can be moderately explained by the contemporary stream network (STREAMTREE analysis, R2 = 0.75). The MEMGENE analysis suggested genetic division between northern (genetic clusters 1 and 2) and southern (clusters 3 and 4) sub-basins. We observed a high degree of genetic admixture in each location, highlighting the importance of natural flooding patterns and possible genetic impacts of supplementary stocking. Insights obtained from this research advance our knowledge of the complexity of a tropical stream system, and guide current conservation and restoration efforts for this species in Thailand.

Effects of arachidonic acid supplementation in maturation diet on female reproductive performance and larval quality of giant river prawn (Macrobrachium rosenbergii)

The giant river prawn (Macrobrachium rosenbergii) is one of the most farmed freshwater crustaceans in the world. Its global production has been stalling in the past decade due to the inconsistent quality of broodstock and hatchery-produced seeds. A better understanding of the role of nutrition in maturation diets will help overcome some of the production challenges. Arachidonic acid (20:4 n-6, ARA) is a fatty acid precursor of signaling molecules important for crustacean reproduction, prostaglandins E and F of the series II (PGE2 and PGF2α), and is often lacking in maturation diets of shrimp and prawns. We examined the effects of ARA in a combination of different fish oil (FO) and soybean oil (SO) blends on females’ reproductive performance and larval quality. Adult females (15.22 ± 0.13 g and 11.12 ± 0.09 cm) were fed six isonitrogenous and isolipidic diets containing one of two different base compositions (A or B), supplemented with one of three levels of Mortierella alpine-derived ARA (containing 40% active ARA): 0, 1 or 2% by ingredient weight. The two base diets differed in the percentages of (FO and SO with diet A containing 2% SO and 2% FO and diet B containing 2.5% SO and 1.5% FO, resulting in differences in proportional contents of dietary linoleic acid (18:2n-6, LOA) and docosahexaenoic acid (22:6n-3, DHA)). After the eight-week experiment, prawns fed diet B with 1 and 2% ARA supplement (B1 and B2) exhibited the highest gonadosomatic index (GSI), hepatosomatic index (HSI), egg clutch weight, fecundity, hatching rate, number of larvae, and reproductive effort compared to those fed other diets (p ≤ 0.05). Larvae from these two dietary treatments also had higher tolerance to low salinity (2 ppt). The maturation period was not significantly different among most treatments (p ≥ 0.05). ARA supplementation, regardless of the base diet, significantly improved GSI, HSI, egg clutch weight and fecundity. However, the diets with an enhanced ARA and LOA (B1 and B2) resulted in the best reproductive performance, egg hatchability and larval tolerance to low salinity. These dietary treatments also allow for effective accumulation of ARA and an n-3 lcPUFA, DHA in eggs and larvae.