Mazlan Abdul Ghaffar

Diadromous life histories—encompassing anadromous, catadromous, and amphidromous modalities—require obligatory ontogenetic migrations across a continuous ecosystem of freshwater, brackish estuaries, and/or marine pelagic zones. Accelerating anthropogenic climate change exposes these species to a compounding multi-stressor environment defined by concurrent marine heatwaves, ocean acidification, or pervasive hypoxia. This makes them vital cross-ecosystem sentinels whose absolute physiological and adaptive boundaries remain critically unquantified. Here, we propose a conceptual paradigm shift: rather than classifying these taxa merely as passive conservation casualties, the scientific community must leverage them as proactive genomic and behavioral roadmaps for climate resilience, owing to their profound intrinsic phenotypic plasticity and highly localized microevolutionary capacities. This framework synthesizes how diadromous fish species can become a future climate-adaptive model organism under various climate-driven conditions. Ultimately, using diadromous species as functional biological models provides the empirical framework needed to optimize financial return on investment for climate-resilient civil infrastructure, preserve vital natural capital subsidies, and decode the precise genetic blueprints required to engineer sustainable aquaculture systems for global food security.

A research expedition evaluates the current fish diversity and abundance in the “UMT mangrove reserve area - UMT-MRA”. Four-sampling survey trips were conducted at three stations on the UMT-MRA, where fish samples were caught using gill nets, traps, and scoop nets. In situ water quality parameters were recorded while one litre of water was collected from each site for nutrients and chlorophyll analysis. Fish community/ environment relationships were evaluated using Pearson Correlation Analysis. A total of 109 fish, representing 19 species from 15 families were captured during the expedition. The most dominant families by species number were Gobiidae (15.8%), followed by Ambassidae and Cichlidae (10.5%). 12 families recorded only one species (5.3%) each. Aplocheilus panchax (18.3%), Terapon jarbua (13.8%), and Ophiocara porocephala (11.9%) were the most abundant species. 10 commercially valuable species were identified and Oreochromis niloticus was categorised as “Vulnerable” (VU) on the IUCN Red List. 15 species were labelled Least Concern (LC) and three were not evaluated (DD). No significant differences among stations were found in water quality parameters, nutrients, and chlorophyll, suggesting minimal influence of abiotic factors. In conclusion, this area is crucial for maintaining a diverse mangrove ecosystem, requiring urgent conservation efforts. More research is needed to understand its significance as a fish-feeding and breeding habitat.

In the aquaculture of fish and crustaceans, the indoor culture of M. macrocopa constitutes a requisite to produce a more effective feed for the larviculture of the cultured commercial species. The present study examined the efficiency of different diets on population density, survival, and productivity of M. macrocopa. The cladocerans [Cladocera: currently largely referred to as Diplostraca] were fed and enriched with seven diets, including Chlorella sp., agro-industrial residues (rice bran and soybean meal), bio-organic fertilizer (chicken manure and swiftlet waste), canola oil and artificial micro pellets. The diets were provided at a concentration of 500 mg/l for each diet. The M. macrocopa fed on rice bran had a higher population density, survival, productivity, and a promising higher nutrient quality than the test groups fed on the other dietary treatments used. This study has covered the most important aspects of nutritional requirements to produce live feed organisms, which would provide a comprehensive data set for an alternative solution of the best feed for M. macrocopa propagation and their utilization in hatcheries.

Aim: Although the underlying biotic and abiotic factors of phylogeographic patterns is an important topic in biogeography, they remain largely unexplored in marine fishes. We empirically investigated the effects of several biological traits on phylogeographic patterns of selected marine fishes. We predict that overall similarity in these traits correlates with similarity in phylogeographic patterns among species, and that genetic diversity and demographic stability are associated with these traits, as well as the local (paleo)environment.Location: Five localities in the South China Sea (SCS).Taxon: Thirteen species of coastal marine fishes.Methods: Phylogeographic Concordance Factors (PCFs) based on mitochondrial DNA sequences were tested for correlation with similarity based on distribution range, depth of occurrence, habitat preference, salinity tolerance and fecundity among the subset of the focal species. The relationship between phylogeographic patterns and these traits was also qualitatively examined. Bayesian model averaging was used to test the association between these traits and the genetic diversity estimates.Results: Pairwise PCFs of five species across all localities were correlated with pairwise biological similarity, with depth and distribution ranges contributing most to the biological similarity. Nucleotide diversity of Indo‐west Pacific species tended to be greater than that of circumtropical species. Populations showing signs of demographic expansions were concentrated in three localities. A novel concordant population break across six focal species and other marine organisms coincided with the dispersal barrier previously suggested by biophysical dispersal modelling.Main conclusions: Abiotic factors were dominant in controlling phylogeographic patterns, with possible contributions from biotic factors. Depth and distribution ranges, or other eco‐physiological traits underlying these, might have influenced the phylogeographic patterns of several species, presumably coupled with historical vicariance. The geography of local populations relative to the shallow continental shelf may explain the heterogeneous demography. Historical vicariance and contemporary ocean currents have contributed to the concordant population break.

Benthic species, though ecologically important, are vulnerable to genetic loss and population size reduction due to impacts from fishing trawls. An assessment of genetic diversity and population structure is therefore needed to assist in a resource management program. To address this issue, the two-spined yellowtail stargazer (Uranoscopus cognatus) was collected within selected locations in the Indo-West Pacific (IWP). The partial mitochondrial DNA cytochrome c oxidase subunit 1 and the nuclear DNA recombination activating gene 1 were sequenced. Genetic diversity analyses revealed that the populations were moderately to highly diversified (haplotype diversity, H = 0.490–0.900, nucleotide diversity, π = 0.0010–0.0034) except sampling station (ST) 1 and 14. The low diversity level, however was apparent only in the matrilineal marker (H = 0.118–0.216; π = 0.0004–0.0008), possibly due to stochastic factors or anthropogenic stressors. Population structure analyses revealed a retention of ancestral polymorphism that was likely due to incomplete lineage sorting inU. cognatus, and prolonged vicariance by the Indo-Pacific Barrier has partitioned them into separate stock units. Population segregation was also shown by the phenotypic divergence in allopatric populations, regarding the premaxillary protrusion, which is possibly associated with the mechanism for upper jaw movement in biomechanical feeding approaches. The moderate genetic diversity estimated for each region, in addition to past population expansion events, indicated thatU. cognatuswithin the IWP was still healthy and abundant (except in ST1 and 14), and two stock units were identified to be subjected to a specific resource management program.

Salinity is a known factor in shaping population dynamics and community structure through direct and indirect effects on aquatic ecosystems. Salinity changes further influence food webs through competition and predation. The responses of Moina macrocopa (Cladocera) collected from Setiu Wetland lagoon (Terengganu) was evaluated through manipulative laboratory experiments to understand the ability of M. macrocopa to tolerate high salinity stress. Specifically, the fatty acid composition, growth, survival, and reproduction of this cladocerans species was examined. Sodium chloride (NaCl) as used in the treatments water with the concentration 0, 4, 6, 8, 12, and 15 salinity. Fatty acid levels were determined using Gas Chromatography and Mass Spectrophotometry (GC-MS). The results indicated that optimal conditions produced the highest fatty acid content, especially the polyunsaturated fatty acid content, such as EPA (eicosapentaenoic acid), ALA (alpha-linoleic acid), ARA (arachidonic acid), and DHA (docosahexaenoic acid). Furthermore, M. macrocopa survival was best at salinity 0, with a percentage of 98%, whereas the opposite occurred at salinity 15, with approximately 20% of viable animals surviving. Besides, M. macrocopa also showed the highest reproduction rate at salinity 0 (e.g., average initial age of reproduction, 4.33 ± 0.58 days) compared with other salinities level. Interestingly, the difference in growth at different salinities was not evident, an unusual finding when considering adverse effects such as osmoregulation pressure on the organism. Based on the results, we conclude that M. macrocopa can only tolerate salinity below salinity 8 and cannot withstand stressful environmental conditions associated with salinities above 8.

Climate warming and low pH environment are known to negatively impact all levels of aquatic organism from cellular to organism and population levels. For ammonotelic freshwater species, any abiotic factor fluctuation will cause disturbance to the fish, specifically at the gills which act as a multifunctional organ to support all biological processes. Therefore, this study was designed to investigate the effect of temperature (28 vs. 32°C) and pH (7.0 vs. 5.0) stress on the gill plasticity of Hoven's carp after 20 days of continuous exposure. The results demonstrated that high temperature and low pH caused severe changes on the primary and secondary lamellae as well as the cells within lamellae. An increasing trend of the proportion available for gas exchange was noticed at high temperature in both pH exposures, which resulted from a reduction of the primary lamellae width with elongated and thinner secondary lamellae compared to fishes at ambient temperature. Following exposure to high temperature and acidic pH, Hoven's carp experienced gill modifications including aneurysm, oedema, hypertrophy, curling of secondary lamellae, epithelial lifting, hyperplasia and lamellae fusion. These modifications are indicators of the coping mechanism of Hoven's carp to the changing environment in order to survive.