Ichthyofaunal diversity with relation to environmental variables in the snow-fed Tamor River of eastern Nepal

Tamor River in eastern Nepal supports diverse hill stream fishes. From winter, spring, summer, and autumn of 2020, we investigated the ichthyofaunal diversity with environmental variables in the snow-fed Tamor River covering four seasons (winter, spring, summer, and autumn) and field surveys were carried out in January, April, July, and October 2020. We used two cast nets of different sizes, one with a mesh size of 2 cm, 6 m diameter and 6 kg weight and another having 0.5 cm, 3 m diameter and 2 kg weight. In addition, monofilament gill nets with mesh sizes of 6, 8, and 10 were used for fish sampling. A total of 6,373 fish individuals representing 28 species belonging to three orders, seven families, and 16 genera were recorded. One-way permutational multivariate analysis of variance (perMANOVA) on the Non-metric Multidimensional Scaling (NMDS) showed no significant (P >0.05) difference between winter, spring, and autumn season but summer season showed significant (P <0.05) difference from winter, spring, and autumn seasons. Furthermore, one-way analysis of variance on redundancy analysis (RDA) vindicated that among the selected parameters, pH, air temperature and total hardness were the influencing factors (P <0.05) to determine the fish community structure in Tamor River.

Fish community structure along altitudinal gradients with relation to environmental variables in Ratuwa River of Eastern, Nepal

Studies on fish community structure along altitudinal gradients of rivers are lacking in Nepal. This study was carried out to gauge the fish diversity and composition along elevational gradient in Ratuwa River. The altitudinal gradient varies between 70 m to 1300 m. Fish samples were collected based on habitat representativeness from April (spring) 10-18, July (summer) 10-18, October (autumn) 10-18, 2020 and January (winter) 10-18, 2021. A total of 3447 specimens representing 4 orders, 14 families and 36 species were identified. Both fish diversity and abundance of studied ichthyofauna vary with altitudinal gradient. The present study affirmed that fish species of Opsarius bendelisis, Schistura multifasciatus, Garra annandalei, Brachydanio rerio, Aspidoparia morar, and Schistura scaturigina are the major contributory species (>1%) for both space and time spectrums. Fish community structure testing for both to space and time showed significant difference in spatial spectrum (R=0.72, P<0.01) but no significant difference in temporal variation (R=-0.034, P>0.05). The present results hinted that fish assemblage structure varied significantly from low to high elevations, altitude, water temperature, water velocity, dissolved oxygen and pH was found as major influential factors (P<0.05) for species distribution.

Environmental DNA Biomonitoring Reveals Seasonal Patterns in Coral Reef Fish Community Structure

Coral reef fish populations are declining due to multiple factors including habitat destruction, overfishing, and climate change. While these can include seasonal impact, seasonal changes can also be a confounding factor, so that seasonal monitoring is essential for detecting true temporal changes in fish community abundance and composition. However, seasonal monitoring is rarely implemented. The aim of this study was to detect the seasonal patterns of coral reef fish community structure around Tidung Kecil Island, Indonesia, using eDNA metabarcoding (eDNA) and underwater visual census (UVC). The UVC identified 32 species belonging to 10 families in the rainy season and 29 species belonging to 7 families in the dry seasons. The eDNA metabarcoding identified 209 species belonging to 56 families and 27 species belonging to 17 families in the rainy and dry seasons, respectively. Based on eDNA metabarcoding data, coral reef fish abundance and community composition differed significantly between seasons (Mann Whitney, p<0.01), while the UVC method did not detect these seasonal differences (Mann Whitney, p>0.05). UVC and eDNA data both showed a predominance of omnivorous fishes in the rainy season and carnivorous fishes in the dry season. Ecological indices did not differ significantly between seasons for either method, although the species making the highest contributions to the similarity (SIMPER) analysis differed between methods. Overall, this study confirms the premise that eDNA metabarcoding can be an effective tool for monitoring seasonal variation in coral reef fish communities.

Relationships between environmental conditions and fish assemblages in the Lohore River of Dailekh, Western Nepal

The Lohore River is one of the important riverine ecosystems of Dailekh which support diverse aquatic communities. The present study was carried out to assess the fish diversity status with relation to environmental conditions in both to space and time. The survey was conducted at three different sampling stations in three different seasons. For the fish sampling, two cast nets of different mesh sizes were used, one having large mesh size of 2 cm, 6 m diameter and 6 kg weight and another having mesh size of 0.5 cm, 3 m diameter and 2 kg weight. Moreover, drag net and gill net were also used to collect the fish samples. A total of 11 fish species belonging to 2 orders, 3 families and 7 genera. Results from the similarity percentage analysis (SIMPER) suggested that fish species of Puntius gelius, Schizothorax plagiostomus, Tor chelynoides and Schistura sovana were major contributing species each contribute more than 9%. An analysis of similarity (ANOSIM) pointed that fish community structure in the Lohore River differ in spatial scale (p<0.01) but not in temporal scale (P>0.01). Water temperature, dissolved oxygen and water velocity was found as influential factors for fish species distribution.

Seasonal Variations In Species Composition And Community Structure In The Eastern Coast of South Korea

The seasonal variations in species composition of set net fisheries were investigated in the eastern coast of Korea, from 2007 to 2008. In total, 51 species were found that were classified into 15 orders and 33 families. The water temperature of the study area was 0.1–2.1 °C during the study period, which was higher than the average water temperature in the last decade. Monthly variation in the number of species peaked twice, in May (spring) and November (autumn) when the water temperature increased and decreased, respectively, and monthly variation in the number of individuals showed a remarkably high trend in winter and autumn and was mainly caused by large migratory species. Based on the cluster analysis of the 18 most dominant species with more than 0.4% of the total number of individuals, we divided the species composition and community structure into three groups: fishes with temporary appearance (Group A), fishes with long-term appearance (Group B), and dominant pelagic fishes appearing with long-term appearance (Group C). We could conclude that seasonal variation in the fish community structure was mainly caused by pelagic migration of species under high water temperature conditions during the study period.

Evaluating the influence of environmental variables on fish assemblages along Tropical Andes: considerations from ecology to conservation

The lack of knowledge about freshwater biodiversity in remote areas like montane Andean rivers is noticeable and hinder the development of efficient conservation plans for aquatic ecosystems. Habitat requirements of tropical Andean fishes have been poorly analysed, despite the relevance of these ecological features on the fish conservation strategies. The present study aimed to examine fish assemblages along the altitudinal gradient in tropical Andean rivers and their relationship to habitat features to detect the most relevant abiotic factors and their implication on conservation. This study was conducted on a regional scale, along six basins located in tropical Andes (500 to 2,692 m a.s.l.). We studied fish diversity and distribution and their habitats along these elevation gradients. We found 6,320 specimens from 53 genera. Our analysis for the six most common and widely distributed genera (Astroblepus, Brycon, Bryconamericus, Chaetostoma, Pimelodella and Trichomycterus) underlines the relevance of hydromorphological variables on fish community structure in the Andean montane rivers, whereas human alterations seem to be less significant. These findings could be useful for current management and conservation strategies considering present threats over tropical montane rivers.

Implications of Community-Based Management of Marine Reserves in the Philippines for Reef Fish Communities and Biodiversity

Overfishing and destructive fishing practices are major threats to marine biodiversity in the Philippines, where over 1.9 million small-scale fishers are supported by these biodiverse marine communities. Nearly 50% of all marine fish capture in the Philippines is from artisanal fisheries, with much of it not reported or under-reported. Marine reserves, where fishing is prohibited have been created in many local government units to help restore and preserve this biodiversity. The success of these marine reserves is still under serious debate with effective management still representing a significant challenge. The lack of a governance system to centrally managed marine reserves has resulted in non-governmental organizations developing community-based management schemes. Using independent fisheries data from Rare’s Fish Forever program, we applied PERMANOVA, SIMPER and biodiversity index analyses to evaluate the community structure of reef fish in 20 sites within the Philippines. We analyzed the differences in fish assemblage inside and outside of these marine reserves, before and after community-based management had been implemented. We provide evidence that: (i) fish community structure changes within marine reserves after community-based management strategies are implemented; and (ii) community-based management of marine fisheries resources protects and promotes biodiversity inside, and in some cases, outside marine reserves. Variability across sites suggests that other social or ecological factors may be influencing the ability of marine reserves to fully protect biodiversity and marine resources. Small-scale fishers in the Philippines participate in mixed-catch harvests and depend on biodiversity and reef community structure for their livelihoods. Thus, this work has implications on how community-based management strategies for marine reserves and adjacent waters may be beneficial for the sustainability of small-scale fishers.

Ecological Indicators for Surface Water Quality - Methodological Approaches to Fish Community Assessments in China and Germany

Assessments of aquatic ecosystem health rely increasingly on biological indicators such as fish community structure, but national approaches differ. To use bioindicators efficiently and to allow cross-country comparisons, standardized tools and methods are required. Within this study, currently applied procedures for stream ecosystem assessment in China and Germany are summarized and active and passive fish sampling methodologies used in both countries are investigated. The methodological comparison was based on the results of a joint Chinese German workshops within the SINOWATER project in 2016. A joint sampling campaign was then conducted in 2017 at 6 representative sites within 70 km of the Fan River, a tributary to the Liao River System in Liaoning province, China. Active methods comprised single-pass electrofishing methods as typically applied in Germany and China as well as seining. As passive methods, common minnow traps, gill-netting and longline-fishing were used. To allow the comparability between methods, a standardized sampling design comprising several replicates at each site was chosen, covering a range of different ecological stream conditions. By comparison of the different fishing methodologies, electrofishing yielded the best overall results to assess fish biodiversity in terms of species abundance, richness and catch per unit effort. Differences in the effectiveness of the different electrofishing approaches mostly depended on the power source used. To cover the full spectrum of the fish community and to detect very rare species, a combination of different active and passive methods was most useful. If electrofishing is the method of choice, it is very important to adjust the gear power to river specific conditions such as flow, size and depth. The results of this joint Chinese-German study may aid in the selection of suitable sampling methods for fish community assessments in the future.