The reproductive aspect of tiny scale barb, Thynnichthys thynnoides (Bleeker, 1852) at Rui River, Perak, Malaysia

This study aims to understand the reproductive biology of Thynnichthys thynnoides at Rui River, Perak, Malaysia. A total sample of 175 individuals, including 83 from Kuala Rui (S1) and 92 from Air Ganda (S2), were collected from local artisanal fishers. Fish was caught using gill nets and scoop nets during migration and spawning seasons (i.e., November to December 2018). For each fish individual, the total length (TL), body weight (BW), and ovary weight (OW) were and. A Chi-square test was performed to evaluate the sex ratio of the studied population. Simple linear regression analysis was used to explain the relationship between absolute fecundity (FA) or relative fecundity (FR) with total length, body weight, and ovary weight. For a coefficient of determination (r2) and correlation coefficient (r), a regression equation was determined. The results showed that the TL of T. thynnoides varied from 13.3 to 20.3 cm, with a calculated mean of 16.78 ± 1.1 cm. Body weights ranged from 31.86 to 78.86 g, with an average body weight of 53.81 ± 10.1 g. The FA ranged from 14454 to 29531 (mean = 21112 ± 4612) eggs per fish, and the FR from this study ranged from 211 to 658 (mean = 358 ± 93), where the OW was more significantly correlated with the absolute fecundity (r>0.513; p<0.001) than other body metrics. Negative allometric growth of T. thynnoides was observed during this study. The overall ratio of the T. thynnoides was 1:0.82 (male: female). In conclusion, this study has shown that the fecundity of the fish population is declining, although the cause is still unclear. The knowledge of this study would help fisheries managers plan necessary regulations for sustainable fishery practice at the Rui and Perak rivers, specifically during the migration and spawning season of T. thynnoides

Evaluating the surrounding physical habitat for Thynnichthys thynnoides's spawning areas using a visual-based habitat assessment at Rui River, Perak

This study was conducted to evaluate the physical habitat of spawning areas for Thynnicthys thynnoides (T. thynnoides) in the Rui River, Gerik, Perak. Five sampling sites of Rui River's floodplain were chosen. Sampling was conducted between May and October 2015 by using a visual-based habitat assessment developed for Rapid Bioassessment Protocols for Use in Streams and Wadeable Rivers: Periphyton, Benthic Macroinvertebrates and Fish. This study showed that T. thynnoides still migrated to the upper stream of Rui River during spawning season mainly in August. Habitat assessment scoring indicated that the physical habitat structure of Rui River fell into a suboptimal category, which was most likely able to support fish populations and thus providing a suitable habitat for T. thynnoides during the spawning season. Conclusively, it was observed that the T. thynnoides population was dependent on environmental conditions

An annotated checklist of fish fauna of Bukit Merah Reservoir and its catchment area, Perak, Malaysia

The fish fauna was surveyed at Bukit Merah Reservoir of Perak (one of the oldest reservoir in Peninsular Malaysia) and its catchment areas. A total of 47 species from 19 families were recorded: 38 fish species were recorded from eight sampling stations located in selected tributaries (lotic zone), while another 25 fish species were recorded in the reservoir itself (lentic zone). Based on a combination of previously published checklists and the present survey, a total of 76 fish species were recorded at Bukit Merah Reservoir. Out of these species, 25 fish species from this survey were new records. Most of the new records were found in the catchment area of the river basin. The presence of two alien species, Oreochromis niloticus and Clarias gariepinus, should be noted as these species could affect the population of native species

Spatial and temporal variations of water quality and trophic status in Bukit Merah Reservoir, Perak

A study of spatial and temporal variations on water quality and trophic status was conducted twice a month from December 2012 to January 2014 in four sampling stations at Bukit Merah Reservoir (BMR). The concentration of dissolved oxygen (DO), water temperature, conductivity, total dissolved solids (TDS), total phosphorous (TP), PO4-, NO2-, NO3-, NH4+ and net primary productivity had significant differences temporally (p<0.05) except for pH, total suspended solids (TSS) and chlorophyll-a. Based on correlation analysis, the amount of rainfall and rain days has negatively correlated with secchi depth and chlorophyll-a (p<0.01). The water level has significantly decreased the value of the temperature, pH, conductivity, TP and NO2- but it has positive correlation with NO3- and NH4+. Discharged from Sungai Kurau increased the value of conductivity, TSS, TP and NO2- as a result from runoff and erosion, thus decreasing the secchi depth values, NO3- and NH4+. The water quality of BMR is classified in Class II and TSI indicates that the BMR has an intermediate level of productivity (mesotrophic) and meets the objective of this reservoir which was to provide water for paddy irrigation

Limnological Influence of Dams Placed in Series along the Perak River, Malaysia

An 18-month study (July 2009 – December 2010) was conducted to determine the influence of four dams located in series along the Perak River, in Malaysia: Temengor, Bersia, Kenering and Chenderoh dams. The framework for investigation centered around the Serial Discontinuity Concept (SDC) and the Cascading Reservoir Continuum Concept (CRCC). In addition to reservoir, tailwater and riverine reach characteristics, the interacting influences of tributary streams and watersheds were addressed. Variables included in-situ environmental physical parameters, nutrients, seston concentration and transport, and fish assemblage characteristics. In-situ variables, water and seston samples, were recorded/collected monthly from all four reservoirs, their associated riverine sections, and their primary tributaries. Fish samples were collected by using experimental gill nets in reservoirs. Fish were enumerated taxonomically and total length and weight were measured for the bony-lipped barb, Osteochilus hasselti (Valenciennes, 1842). Hypotheses were tested using analyses of variance with permutations. Relationships were determined using correlation, and multivariate and regression analyses. The integrated influences of discontinuity and cascading on nutrient and seston transport dynamics and fish assemblages (except for relative condition and biomass of O. hasselti) were operative in dynamic juxtaposition along the river’s continuum, and depended on distance between dams and presence and size of tributary streams. However, principal tributaries along the four serial dams in the Perak River appeared to have little spatial influence on their respective system’s nutrient and seston dynamics due to dilution effects of mainstem discharges. Among all tributaries, only the Rui River depicted reversal of the serial discontinuity trend in its system. Even so, its influence on its system was limited. Effects of ecosystem fragmentation along the river’s continuum on in-situ, nutrients and seston transport dynamics, and fish assemblages existed, but not necessarily in line with the SDC nor in line with the CRCC. The dynamics of in-situ, nutrient, seston and fish assemblage parameters were more associated with land use, reservoir surface area and dam discharge. Results from this study generated a hypothesis that submerged woody vegetation in the reservoirs may augment and compensate lost nutrients, thereby minimizing functional impacts of serially-arranged dams

Fish composition and diversity in Perak, Galas and Kelantan Rivers (Malaysia) after the major flood of 2014

Fish from three major rivers, namely the Kelantan River (KR) and the Galas River (GR) in Kelantan, and the Perak River (PR) in Perak, Malaysia, were caught using gill nets with different mesh sizes, cast nets, and the electroshock method. There were 14 fishes representing five families and five fish species were collected from the Kelantan systems in February 2015. While the Galas system holds more fish, 48 individual fishes comprising of four families and 10 fish species were found there. A total of 213 fish specimens representing 10 families and 22 species were captured in PR in May 2015. For diversity index, PR had the highest value due to the catchment area and the environmental condition: Shannon-Weiner index (H’) (2.54), Species Evenness (J’) (0.73) and Simpson’s Dominance (D’) (8.93), compared to GR (H’) (2.09) (J’) (0.603) (D’) (6.52) and KR (H’) (1.62) (J’) (0.47) (D’) (5.62)

Assessing Diet & Trophic Position of Fish in Chenderoh Reservoir, Malaysia: SCA & SIA Approach

The present study assessed and compared the diet and trophic positions (TP) of two carnivorous fish H. macrolepidota and C. ocellaris from Chenderoh Reservoir, Malaysia. The focal goal of the study was to understand the effects of invasive non-indigenous species (NIS), C. ocellaris, on the native indigenous (IS) fish species, H. macrolepidota. Data were acquired from September 2014 to February 2015 within the study area. The assessment was grounded in stomach content analysis (SCA) and stable isotope analysis (SIA), which collectively clarified the feeding habits and trophic positions (TP) of these selected fish. In total, 184 fish samples (comprising 64 individuals of H. macrolepidota and 120 individuals of C. ocellaris) underwent stomach content analysis (SCA). Additionally, 24 individuals (12 of H. macrolepidota and 12 of C. ocellaris), sampled from December 2014 to February 2015, were selected for stable isotope analysis (SIA). The mean RGL values for H. macrolepidota and C ocellaris were 0.98 ± 0.18 and 1.10 ± 0.15 (Mean ± SD), respectively, aligning with known ranges for carnivorous fish. These values also clarified that both species occupy higher TP in the food web as tertiary or quaternary consumers. SCA findings also revealed that fish and crustaceans were the predominant food categories for H. macrolepidota, while C. ocellaris predominantly fed on fish. The mean stomach fullness index (MSF) and the gastrosomatic index (GSI) corroborated the differences in the foraging performance of the fishes, with C. ocellaris having a higher MSF (2.03) compared to H. macrolepidota (0.65). These implied that C. ocellaris had plentiful of food and encountered fewer diet-related challenges in the ecosystem. From SIA, δ13C values indicated that the primary carbon sources for both species are C3 plants, particularly aquatic vegetation. Further, δ15N values further ensured that both H. macrolepidota and C. ocellaris are carnivorous in nature and occupy higher TP in the ecosystem