Northern Rivers Research Articles

Spatial distribution, source analysis, and ecological risk assessment of PBDEs in river sediment around Taihu Lake, China.

The distribution and composition of organic pollutants in sediment are affected by the source and regional environment. To understand the characteristics and risk of polybrominated diphenyl ethers (PBDEs) in the area around Taihu Lake, composite sediment samples (n = 41) were collected in rivers around Taihu Lake to explore the level, spatial distribution, and source of PBDEs. The results showed that the most abundant BDE congener in river sediment was BDE209, followed by BDE99 and BDE47, with median values of 48.7, 2.17, and 1.52ngg-1, respectively. Concentrations of PBDEs in sediments from northern rivers were significantly higher than those from other areas, but the overall risk was at a moderate-lower level compared with research results in other references. Results of principle component analysis (PCA) and source characteristics analysis revealed that most of PBDEs in river sediments around Taihu Lake were mixture of multiple sources, which mainly originated from atmospheric deposition, industrial wastewater, and municipal sewage. TOC showed good correlations with most PBDEs, which implied that PBDE components were influenced by sediment organic matter. Meanwhile, the risk of PBDEs in river sediments in this study area is a moderate-lower level.

Drought alters the biogeochemistry of boreal stream networks

Drought is a global phenomenon, with widespread implications for freshwater ecosystems. While droughts receive much attention at lower latitudes, their effects on northern river networks remain unstudied. We combine a reach-scale manipulation experiment, observations during the extreme 2018 drought, and historical monitoring data to examine the impact of drought in northern boreal streams. Increased water residence time during drought promoted reductions in aerobic metabolism and increased concentrations of reduced solutes in both stream and hyporheic water. Likewise, data during the 2018 drought revealed widespread hypoxic conditions and shifts towards anaerobic metabolism, especially in headwaters. Finally, long-term data confirmed that past summer droughts have led to similar metabolic alterations. Our results highlight the potential for drought to promote biogeochemical shifts that trigger poor water quality conditions in boreal streams. Given projected increases in hydrological extremes at northern latitudes, the consequences of drought for the health of running waters warrant attention.

Endocrine disrupting compounds, pharmaceuticals and personal care products in the aquatic environment of China: Which chemicals are the prioritized ones?

Endocrine disrupting compounds (EDCs), pharmaceuticals and personal care products (PPCPs) have been of great concern as emerging contaminants of aquatic environment. Therefore, there is an urgent need to identify top contaminants so as to allocate better management measures. A list of 77 pharmaceuticals, 20 personal care products (PCPs) and 36 EDCs that were frequently detected in Chinese surface waters was examined in this study. The reported chemicals were concentrated in the highly populated and industrialized areas of China (e.g. the Bohai region, Yangtze River Delta and Pearl River Delta). The concentrations of EDCs and PPCPs were closely related to human domestic sewage and industrial wastewater discharge, and they were generally higher than or at least comparable to most of global rivers. Based on the proximity between the medians of reported exposure concentrations and effect concentrations, the risk ranking results showed that EDCs, e.g. estrone (E1), estriol (E3), 17α-ethynylestradiol (EE2), and PCPs, e.g. triclocarban (TCC), triclosan (TCS), were deemed to represent higher risks to aquatic organisms across China, as well as the Northern rivers (including the Bohai region), Yangtze River Basin, and Pearl River Basin. Pharmaceuticals posed relatively lower risks to organisms owing to their higher effect concentrations. By comparison, the Northern rivers were hotspots where many chemicals were identified as posing greater risks than the Yangtze River Basin and Pearl River Basin. Fish was the most sensitive taxa to 17β-estradiol (βE2) and EE2, which was almost 100,000 times higher risk than algae and worms. Atrazine (ATZ) and galaxolide (HHCB), posed comparably higher risks to algae and worms. The results of this work provide a sound guidance for future monitoring and management of chemicals in China.

Mapping and Damage Assessment of “Royal” Burial Mounds in the Siberian Valley of the Kings

The Valley of the Kings in Tuva Republic, southern Siberia, is arguably one of the most important archaeological landscapes in the eastern Eurasian steppes. Nonetheless, little information exists about the spatial characteristics and preservation conditions of this burial ground consisting of large “royal” mounds. We map the large monuments of the Uyuk Valley’s northern river terrace and assess their state of preservation based on high-resolution optical satellite data. The burial site consists of several hundred mounds, over 150 of them with diameters of more than 25 m, the largest monuments are bigger than 100 m in diameter. This makes the Valley of the Kings in Tuva Republic one of the largest Early Iron Age burial sites in the Eurasian steppes. Unfortunately, around 92% of the large monuments are in bad condition, mostly due to looting.

Optimal Background Color for Head-Starting Northern River Terrapins (Batagur baska Gray, 1831).

Simple SummarySubstrate color is an important physical condition affecting the lifestyle of reared animals. However, no prior data are available regarding northern river terrapins. In this study, the terrapins were reared in five types of colored tanks (transparent, green, red, blue, and black) for twelve weeks. Based on parameters assessing survival, growth, feed utilization, and health, the blue background is more suitable for rearing terrapins relative to other colored tanks. The findings from the current study could be applied to wall, pond, or aquaria decoration to support the head-starting programs of northern river terrapins before release to natural habitat, as well as in public displays, such as aquaria and zoos. Background color has significant effects on the lifestyles of various animal species. In this study, the effects of wall background color on growth, feed utilization, specific activity of gastric and pancreatic enzymes in fecal samples, fecal thermal properties, carapace elemental profile, and hematological parameters were investigated in northern river terrapin (Batagur baska Gray, 1831) in order to optimize the head-starting conditions. The terrapins (70.13 ± 0.04 g initial weight) were completely randomized into five types of colored tanks (transparent, green, red, blue, and black) and reared for twelve weeks. At the end of the experiment, tank color had no effect on survival and growth performance, but had significant effects on feeding rate, feed conversion ratio, and protein efficiency ratio (p < 0.05). Terrapins reared with black, red, or blue backgrounds had the highest feed utilization among the treatments. Among these three groups, analysis of specific activity of gastric and pancreatic enzymes in fecal samples and fecal thermal properties suggested improved digestive functionality in terrapins reared with a blue background relative to the other treatments. Carapace elemental composition and hematological parameters indicated no negative effects on health status of the terrapins reared with this optimal treatment. Findings from the current study support the head-starting program of northern river terrapins before release to natural habitats, and could also be applied in aquaria or zoos for public display.

Impacts of future climate on the hydrology of a northern headwaters basin and its implications for a downstream deltaic ecosystem

AbstractAnthropogenic and climatic‐induced changes to flow regimes pose significant risks to river systems. Northern rivers and their deltas are particularly vulnerable due to the disproportionate warming of the Northern Hemisphere compared with the Southern Hemisphere. Of special interest is the Peace–Athabasca Delta (PAD) in western Canada, a productive deltaic lake and wetland ecosystem, which has been recognized as a Ramsar site. Both climate‐ and regulation‐induced changes to the hydrological regime of the Peace River have raised concerns over the delta's ecological health. With the damming of the headwaters, the role of downstream unregulated tributaries has become more important in maintaining, to a certain degree, a natural flow regime, particularly during open‐water conditions. However, their flow contributions to the mainstem river under future climatic conditions remain largely uncertain. In this study, we first evaluated the ability of a land‐surface hydrological model to simulate hydro‐ecological relevant indicators, highlighting the model's strengths and weaknesses. Then, we investigated the streamflow conditions in the Smoky River, the largest unregulated tributary of the Peace River, in the 2071–2100 versus the 1981–2010 periods. Our modelling results revealed significant changes in the hydrological regime of the Smoky River, such as increased discharge in winter (+190%) and spring (+130%) but reduced summer flows (−33%) in the 2071–2100 period compared with the baseline period, which will have implications for the sustainability of the downstream PAD. In particular, the projected reductions in 30‐day and 90‐day maximum flows in the Smoky River will affect open‐water flooding, which is important in maintaining lake levels and connectivity to perimeter delta wetlands in the Peace sector of the PAD. The evaluation of breakup and freeze‐up flows for the 2071–2100 period showed mixed implications for the ice‐jam flooding, which is essential for recharging high‐elevation deltaic basins. Thus, despite projected increase in annual and spring runoff in the 2071–2100 period from the Smoky sub‐basin, the sustainability of the PAD still remains uncertain.

Provenance of Triassic sandstones in the basins of Northern Ireland—Implications for NW European Triassic palaeodrainage

Palaeodrainage models for the mixed fluvial‐aeolian systems, which supplied detritus to Triassic basins on and offshore Britain and Ireland are well established. Basins such as those across Northern Ireland are not as well understood. Provenance studies of Triassic sandstones in the Slyne Basin offshore western Ireland and in basins west of Shetland have indicated that sediment supply was through a southward flowing fluvial system. Similar work on Triassic sandstones in the Wessex and East Irish Sea basins on and offshore Britain identified source rocks to the south supporting models, which evoke the northward flowing “Budleighensis” river system. The basins across Northern Ireland are potentially situated along the drainage divide between these two large‐scale drainage systems. K‐feldspar Pb‐isotopic analysis, apatite U–Pb geochronology and trace element geochemistry identify the Hebridean Platform, and the Scottish and Irish massifs to the north and west, respectively, and the remnant Variscan Uplands to the far south of the basins as source areas. The proportion of the northern‐ and southern‐derived detritus fluctuates several times over the sampled intervals, suggesting the dominance of drainage systems supplying sand to the basins “switched” intermittently over time. This may be due to abnormally heavy rains periodically powering the Budleighensis river system farther north or perhaps localised subsidence temporarily disconnecting Triassic basins on and offshore Britain and Ireland. The Triassic basins in Northern Ireland acted as either a major drainage divide between southern and northern river systems or as a regional sink for sediment preventing further expansion of either system.

ON THE INFLUENCE OF ICE COVER ON THE UNDERGROUND COMPONENT OF RIVER FLOW

The river network is the main drainage of underground waters of the territories. It is created over a long period and is determined by geological, climatic and orographic conditions. The draining capacity of a hydrographic network depends not only on its density, but also on the speed of water flowing down it. The latter is determined by the area of the living section, slope, roughness of the riverbed. The article shows that the river ice of the Northern rivers, as a seasonal hydraulic resistance, can also have a significant impact on the drainage capacity of the hydrographic network. On the example of river flow in warm and cold winters, it is shown that the ice cover regulates the participation of groundwater at different levels of drainage in the formation of river flow. As the climate warms, the regulatory role of the ice cover decreases. The rate of underground water treatment in the upper sections of river basins increases, accompanied by an increase in water content in the lower parts of the hydrographic network. Over the past 30-40 years, the contribution of groundwater in the watershed of the river basins to the supply of rivers in the forest zone in mezhen decreased by 20% compared to the previous quasi-stationary climate period. There is a drying of the upper reaches of river basins, despite the growth of annual precipitation. In the future, if the current trends of climate change continue, it is possible to further reduce the underground supply of rivers, as the drainage role of the hydrographic network will increase. The reduction of groundwater reserves in river basins will reduce their regulatory role in river flow and may increase the frequency of occurrence of extremely low water content. This should be taken into account when developing adaptive water management measures to climate change.

Does a sum of toxic units exceeding 1 imply adverse impacts on macroinvertebrate assemblages? A field study in a northern Japanese river receiving treated mine discharge.

In ecological risk assessment, sum-of-toxic-unit approaches based on measured water quality factors such as trace metals are used to infer ecological impacts in the environment. However, it is uncertain whether the use of such approaches yields accurate risk predictions. To address this issue, we investigated and compared (1) water quality, including trace metals, and (2) benthic macroinvertebrate communities in a northern Japanese river receiving treated discharge from an abandoned mine and in a nearby reference river. As a sum-of-toxic-unit approach, we employed a cumulative criterion unit (CCU), namely, the sum of the ratios of the dissolved concentrations of a metal (Cu, Zn, Cd, or Pb) divided by the US Environmental Protection Agency hardness-adjusted environmental water quality criterion for that metal. Compared with the reference sites, at the metal-contaminated sites, the richness, abundance, and structure of macroinvertebrate communities were little affected, with CCUs of 1.7 to 7.4, suggesting that CCU values exceeding 1 do not always indicate marked adverse impacts on these metrics. Further study is still required to derive a more compelling conclusion on the generally applicable relationships between CCUs and ecological impacts on river invertebrates. This would lead to better ecological risk assessments based on sum-of-toxic-unit approaches.

Genetic patterns reveal northward range expansion and cryptic diversity in Nalbant’s spined loach, Cobitis nalbanti sensu lato (Teleostei: Cypriniformes: Cobitidae)

The morphologically similar populations of the Korean freshwater spined loach recently described as a new species Cobitis nalbanti (Actinopterygii: Cypriniformes: Cobitidae) inhabit the rivers and streams on the Korean Peninsula that flow into the Yellow Sea and the Korea Strait. These shallow sea areas have experienced recurrent sea-level rises and falls. In this study, we investigate the impact of repeated disconnection and reconnection of rivers on the population genetics and morphological variation of C. nalbanti. A total of 264 individuals of C. nalbanti were collected from 17 localities covering the entire distribution range of this species in South Korea. We examined multi-locus genetic data including a mitochondrial gene, seven nuclear genes and eight microsatellite loci, and scrutinized 31 morphological variables based on 26 morphometric and 3 meristic characters. We uncovered a population genetic structure and noticeable morphological variation among populations approximately corresponding to the geography of river basins along the Yellow Sea. Overall genetic diversity was significantly reduced in the more northern populations, suggesting range expansion from ancestral southern populations into northern rivers via the paleo-Yellow River system in the Yellow Sea during glacial periods of lowered sea levels. A northward range expansion hypothesis was strongly supported by the reconstruction of geographic ranges of ancestral species and/or populations based on phylogenetic analyses. Both mitochondrial and nuclear phylogenetic trees revealed a relatively highly divergent lineage of C. nalbanti in the southernmost populations (Tamjin lineage). Noticeable differences in morphological variables between the Tamjin lineage and other lineages of C. nalbanti also suggest potential separate specific status of the former. The close phylogenetic relationships between the Tamjin lineage and the Japanese species of Cobitis signify interaction or exchange between the Korean and Japanese cobitids and imply that there was historically at least one freshwater passage on the terrestrial bridge between the Korean Peninsula and the southwestern part of the Japanese archipelago.

Sea catfishes (Ariidae) feeding on freshwater floodplains of northern Australia

Flooding of the terminal floodplains of northern Australian rivers provides a greatly expanded, productive habitat accessed by both freshwater and estuarine fishes. This study aimed to determine the extent to which sea catfishes (Ariidae) make use of floodplains and the reasons for doing so (i.e. spawning, feeding). Nine species were collected from floodplains and adjacent distributaries of the Mitchell and Flinders rivers; floodplain use was largely restricted to freshwater species. Evidence of prior wet season spawning was recorded for some species, and mesenteric lipid deposits indicated that fish were in good condition. However, little evidence of spawning on floodplains was found. Stomach content analysis and stable isotope analysis indicated dietary partitioning, particularly between freshwater and estuarine species, but also within freshwater species, and indicated that some species were responsive to variations in food availability. Isotope analyses suggest extensive movement between freshwater, estuarine and marine habitats at different life history stages for the catfish assemblage studied. Terminal floodplains of northern Australian rivers provide important temporary habitat for adult sea catfishes to feed upon, but do not appear to be used as spawning grounds.

Benthic macroinvertebrate communities in sites with native forest presence and absence in north Patagonia

ABSTRACT The benthic fauna in northern Patagonian streams is characterized by presence of water quality indicator species. The aim of the present study was characterized the benthic communities in streams associated to sites with presence of Nothofagus forests and with human intervention without Nothofagus forests using null models in ecology, unified neutral theory of biodiversity (UNTB) and unweighted pair group method with arithmetic mean (UPGMA). The results of species co-occurrence null model revealed that species associations are random, whereas the results of niche overlap null models revealed the presence of niche overlap. The UNTB results revealed low species number. The results of UPGMA revealed that species composition is specific for each site existing marked differences. The exposed results agree with results observed for central and northern Patagonian Chilean rivers, where the species composition is variable in according to surrounding basin properties and seasonal conditions.

Size, growth and mortality of riverine golden perch (Macquaria ambigua) across a latitudinal gradient

Effective fisheries management requires fish size, growth and mortality information representative of the population and location of interest. Golden perch Macquaria ambigua is long lived, potamodromous and widespread in the Murray–Darling Basin (MDB), Australia. Using a sample spanning 13 river systems and 10° of latitude, we examined whether the maximum size of golden perch differed by latitude and whether growth and mortality varied between northern and southern MDB regions. The length, weight and age ranges of golden perch sampled (n=873) were 52–559mm, 2–3201g and 0+ to 26+ years respectively, and maximum length and weight were unaffected by latitude. Length and age–length distributions represented by age–length keys varied by region, with greater variability in age-at-length and a larger proportion of smaller individuals in northern MDB rivers, which generally exhibit greater variability in discharge. Growth and mortality rates were similar between regions, and an MDB-wide von Bertalanffy growth model (L∞=447, k=0.32 and t0=–0.51) and instantaneous mortality rate (Z=0.20) best described the data. An MDB-wide length–weight equation also provided the best fit (W=6.76×10–6 L3.12). Our data suggest that the MDB can be treated as one management unit in terms of golden perch maximum size, growth and mortality parameters.

Северное речное пароходство в годы Великой Отечественной войны (1941–1945 гг.)

Северное речное пароходство в годы Великой Отечественной войны (1941–1945 гг.)

On the myths in hydrology and in other earth sciences

Following scientific myths, which are widely spread in hydrology and in other earth sciences, are discussed. (1) The total water mass on land surface statistically significantly diminishes during last century. (2) Many time series of annual river runoff demonstrate nonstationary character. (3) The first-order Markov chain is a dominating model in the stochastic description of the long time series of annual runoff. (4) Because of the global heating, annual discharges of the northern rivers will inevitably grow during the 21st century. (5) The main contribution to uncertainty of the forecast of the runoff through the end of the 21st century is made by uncertainty in scenarios of emission of greenhouse gases and divergences in results of modeling of the climatic system by GCMs. (6) The most shocking myth: the idea of the deterministic positive trend within the mean global temperature during last 100 years.

Evaluating climate and water regime transformation in the European part of Russia using observation and reanalysis data for the 1945–2015 period

ABSTRACT The river runoff regime significantly changed worldwide in the end of twentieth – the beginning of twenty-first century. In the European part of Russia the current changes are manifested in different ways in various regions. The main trend that is observed for most river basins is the ‘levelling’ of annual hydrographs. The interception of melt water during occasional thaw floods has resulted in a decrease in river runoff during the spring months. Simultaneously an increase in the low water period during winter and summer occurred. Reducing in the depth of soil freezing, caused by warm winters, lead to higher groundwater replenishment. At the same time, the loss of melt water to surface retention as well as evaporation has increased. Almost in all seasons of the year the number of occasional flood peaks increases. Occasional floods are superimposed both on the rise and the decline of seasonal snowmelt flood wave, making it difficult to separate it as an independent phase of the water regime. Changes in seasonal characteristics of river runoff are the most evident in the Don and Oka basins. A significant transformation of the water regime is observed in the north-west of European Russia as well. To a lesser extent, the described patterns are typical for the northern rivers and the eastern part of the European Russia – the Kama and the Ural Basin.

Long-Term Changes in the Course of Ice Phenomena on the Oder River along the Polish–German Border

Ice phenomena are a major component of the hydrological regime of east-central and northern European rivers. However, their occurrence disturbs inland water transportation, particularly affecting the major rivers of the Central European Plain that are part of Europe’s international waterways. The Oder is one of these rivers, and is located on the boundary between the much warmer and the much colder part of the temperate climatic zone. This makes the course of ice phenomena on the river difficult to predict. The main purpose of this work is to document and analyse the dynamic of changes occurring for over 60 years (1956–2015) in the ice phenomena of a river that demonstrates a transitional ice regime. It was found that the duration of all ice phenomena decreased (by up to 0.58 days·year−1) and so did the duration of ice cover (by up to 0.46 days·year−1). The rates and trends of the two parameters were, however, different in different parts of the lower stretch of the river. This fact is especially important in the context of climate changes whose characteristics include an increased incidence of extreme weather situations, both meteorological and hydrological. There was also found to be a strong correlation (R2 from 0.69 to 0.81) between the duration of ice phenomena and the mean air temperature in winter (December to February) and a much weaker correlation between the duration of ice phenomena and the NAO index (R2 from 0.42 to 0.48). Such a little correlation of ice phenomena with NAO is likely to result from the pollution of the Oder River (in particular in the second half of the twentieth century) and icebreaking operations on the river.

Optimization of techniques and procedures for the production and management of live feed used in the larval culture of the freshwater shrimp Cryphiops caementarius (Decapoda: Palaemonidae)

The variation in saline requirements during larval development of Cryphiops caementarius establishes a particular coexistence in the culture systems between the shrimp larvae, the microalgae and Artemia nauplii. Although the technology for the mass production of freshwater prawn juveniles has advanced positively, the non-commercial availability of an exclusive live feed for amphidromous crustaceans, such as C. caementarius , has created the need to optimize the management of organisms commonly used as feed in the larval culture of marine crustaceans. We investigated the effect of salinity on embryonic development dynamics and the hatching rate of commercial Artemia sp. cysts, including the effect of cooling decapsulated cysts on the hatching rate, and the effect of salinity on the behavior of marine microalgae used as live feed in the larviculture of C. caementarius . The results encourage a sustained and stable production of Artemia nauplii at different salinities, and at the same time, reduce by 80% the daily time used in feeding activities. Also, the information generated in this study adds critical information about activities and procedures for the larviculture of the northern river shrimp, which could be used to improve larval feeding strategies either in C. caementarius or in other amphidromous crustacean species.

Myxozoan biodiversity in mullets (Teleostei, Mugilidae) unravels hyperdiversification of Myxobolus (Cnidaria, Myxosporea).

Mullets are ecologic and commercially important fish species. Their ubiquitous nature allows them to play critical roles in freshwater and marine ecosystems but makes them more vulnerable to diseases and parasitic infection. In this study, a myxozoan survey was performed on three species of mullet captured from a northern Portuguese river. The results disclose a high biodiversity, specifically due to the hyperdiversification of Myxobolus. Thirteen new species of this genus are described based on microscopic and molecular procedures: 7 from the thinlip grey mullet Chelon ramada, 2 from the thicklip grey mullet Chelon labrosus, and 4 from the flathead grey mullet Mugil cephalus. Myxobolus exiguus and Ellipsomyxa mugilis are further registered from their type host C. ramada, as well as six more myxospore morphotypes that possibly represent distinct Myxobolus species. Overall, the results obtained clearly show that the number of host-, site- and tissue-specific Myxobolus spp. is much higher than what would be expected in accordance to available literature. This higher biodiversity is therefore discussed as either being the result of the usage of poor discriminative criteria in previous studies, or as being a direct consequence of the biological and ecological traits of the parasite and of its vertebrate and invertebrate host communities. Bayesian inference, maximum likelihood and maximum parsimony analyses position the new species within a clade comprising all other Myxobolus spp. that infect mugiliform hosts, thus suggesting that this parasitic group has a monophyletic origin. Clustering of species in relation to the host genus is also revealed and strengthens the contention that the evolutionary history of mugiliform-infecting Myxobolus reflects that of its vertebrate hosts. In this view, the hyperdiversification of Myxobolus in mullet hosts is hypothesized to correlate with the processes of speciation that led to the ecological plasticity of mullets.

5334000-53340000Optimal Salinity for Head-Starting Northern River Terrapins (Batagur baska Gray, 1831).

Simple SummaryNorthern river terrapins can adapt physiologically or behaviorally across a salinity gradient, so that they can move between freshwater habitats and brackish water or estuaries. However, there is no available information on the optimal salinity of this species for supporting captive husbandry programs before release to natural habitat. In the current study, the optimal salinity for the terrapins was investigated to serve the well-being of turtles. At the end of the rearing period, various observed parameters related to growth, feed utilization, and health indicated that optimal salinity for rearing the terrapins is about 4 ppt, while rearing in freshwater (0 ppt) or other brackish (8 and 12 ppt) water conditions had negative effects on some key parameters that reflect well-being. A polynomial regression fit to terrapin weight gain as function of salinity predicts the optimal salinity as 4.35 ppt. Findings from the current study could be directly used in ex situ conservation programs of northern river terrapins before release to natural habitat. Additionally, concurrent conservation and restoration of the wild habitats with preferred salinity is essential for flourishing terrapin population.Northern river terrapins (Batagur baska Gray, 1831) are Asia’s largest turtles living in both freshwater and brackish water. In the current study, the optimal salinity for head-starting programs of this critically endangered species was investigated in order to serve the well-being of turtles before release to natural habitat. Forty-eight terrapins (54.64 ± 0.18 g initial body weight) were randomly distributed to four salinity levels (0, 4, 8, and 12 ppt) and reared for eight weeks, using three replicates with four terrapins each. At the end of rearing trial, growth performance and feed utilization parameters were superior in terrapins reared at 4 ppt, followed by 8 ppt in the rank order of treatments. Negative stress responses were observed in terrapins reared at 12 ppt, as the fecal activity of amylase-to-trypsin ratio was changed significantly, but not that of proteolytic enzymes. The fecal thermal transition properties indicated an abundance of nutrients in the post-absorptive phase for terrapins reared at 4 ppt, followed by the 8 ppt treatment group. The preferred 4 ppt salinity had no negative effects on the health status of the terrapins in terms of carapace elemental composition or hematological parameters. Second-order polynomial regression suggests 4.35 ppt as the optimal salinity for maximal weight gain. Findings from the current study could be directly used in ex situ conservation programs of northern river terrapins before release to natural habitat.