Fishing cat Prionailurus viverrinus distribution and habitat suitability in Nepal

The fishing cat Prionailurus viverrinus is a wetland specialist species endemic to South and Southeast Asia. Nepal represents the northern limit of its biogeographic range, but comprehensive information on fishing cat distribution in Nepal is lacking. To assess their distribution, we compiled fishing cat occurrence records (n = 154) from Nepal, available in published literature and unpublished data (2009–2020). Bioclimatic and environmental variables associated with their occurrence were used to predict the fishing cat habitat suitability using MaxEnt modeling. Fishing cat habitat suitability was associated with elevation (152–302 m), precipitation of the warmest quarter, i.e., April–June (668–1014 mm), precipitation of the driest month (4–7 mm), and land cover (forest/grassland and wetland). The model predicted an area of 4.4% (6679 km²) of Nepal as potential habitat for the fishing cat. About two‐thirds of the predicted potentially suitable habitat lies outside protected areas; however, a large part of the highly suitable habitat (67%) falls within protected areas. The predicted habitat suitability map serves as a reference for future investigation into fishing cat distribution as well as formulating and implementing effective conservation programs in Nepal. Fishing cat conservation initiatives should include habitats inside and outside the protected areas to ensure long‐term survival. We recommend conservation of wetland sites, surveys of fishing cats in the identified potential habitats, and studying their genetic connectivity and population status.     

Spawning Site Selection and Contingent Behavior in Common Snook,Centropomus undecimalis

Reproductive behavior affects spatial population structure and our ability to manage for sustainability in marine and diadromous fishes. In this study, we used fishery independent capture-based sampling to evaluate where Common Snook occurred in Tampa Bay and if it changed with spawning season, and passive acoustic telemetry to assess fine scale behavior at an inlet spawning site (2007–2009). Snook concentrated in three areas during the spawning season only one of which fell within the expected spawning habitat. Although in lower numbers, they remained in these areas throughout the winter months. Acoustically-tagged snook (n = 31) showed two seasonal patterns at the spawning site: Most fish occurred during the spawning season but several fish displayed more extended residency, supporting the capture-based findings that Common Snook exhibit facultative catadromy. Spawning site selection for iteroparous, multiple-batch spawning fishes occurs at the lifetime, annual, or intra-annual temporal scales. In this study we show colonization of a new spawning site, indicating that lifetime spawning site fidelity of Common Snook is not fixed at this fine spatial scale. However, individuals did exhibit annual and intra-seasonal spawning site fidelity to this new site over the three years studied. The number of fish at the spawning site increased in June and July (peak spawning months) and on new and full lunar phases indicating within population variability in spawning and movement patterns. Intra-seasonal patterns of detection also differed significantly with sex. Common Snook exhibited divergent migration tactics and habitat use at the annual and estuarine scales, with contingents using different overwintering habitat. Migration tactics also varied at the spawning site at the intra-seasonal scale and with sex. These results have important implications for understanding how reproductive behavior affects spatio-temporal patterns of fish abundance and their resilience to disturbance events and fishing pressure.     

Climate change and condition of herring (Clupea harengus) explain long-term trends in extent of skipped reproduction

It is commonly assumed that iteroparous fish, once mature, normally reproduce in all consecutive seasons. Recent work has suggested, however, that in Norwegian spring-spawning herring—a population that undertakes extensive spawning migrations—almost one in two adults may skip their second spawning migration. Why should herring not return to spawn the year after first spawning, but instead wait an extra year? For herring, participation in distant, energetically costly, and risky spawning migrations will only pay off in terms of fitness if individuals are sufficiently large, and in sufficient condition, to both successfully migrate and spawn. Changes in the environment and individual condition should therefore affect the likelihood of skipped spawning. This paper describes long-term changes in the extent to which the second reproductive season is skipped in this herring population. These are shown to be linked to the size and condition of herring as first-time spawners, and to climatic factors possibly related to food availability. The findings corroborate the hypothesis that skipped reproduction results from trade-offs between current and future reproduction, growth and survival.     

Effects of Salinity on Acetylene Reduction (Nitrogen Fixation) and Respiration in a Marine Azotobacter

An acetylene-reducing (nitrogen-fixing) bacterium, identified as Azotobacter sp., was isolated from a site in the Canary Creek Marsh, Del. Acetylene reduction activity of the isolate was maximal at 15 to 25‰ NaCl, with no activity observed at 0 or 60‰. Respiration studies showed similar results, with maximal activity occurring at a slightly lower salinity (10 to 20‰ NaCl). The salinities over which peak activity occurred fell within the normal range of in situ salinity (20 to 28‰ total salinity).     

Pheromone-Induced Spawning of Pacific Herring

A spawning pheromone in the milt (semen) and testes of the Pacific herring,Clupea harengus pallasi,is thought to facilitate school spawning of this species. We found that responsiveness to the spawning pheromone was variable among ripe fish (milt-producing or ovulated). Measurement of five principle reproductive steroids in the free form and five steroids in conjugated forms in the plasma of male fish early in the spawning season (newly ripe fish) showed that elevated plasma levels of 3α,17α-dihydroxy-5β-pregnan-20-one and 17α-hydroxyprogesterone coincided with responsiveness to the spawning pheromone in these fish; levels of other steroids did not differ. In contrast, responsiveness to the pheromone by female fish later in the spawning season (ripe-and-holding fish) coincided with lower levels of glucuronated 17α,20β-dihydroxyprogesterone and a lower gonadosomatic index. We suggest that these differences indicate a more advanced mature reproductive state in the responsive individuals among both the newly ripe male and the ripe-and-holding female fish. We found no differences in the level of cortisol in the blood of the herring that could be correlated with differences in pheromonal responsiveness. We conclude that differences in responsiveness to the spawning pheromone coincide to some extent with levels of reproductive maturation but probably not with recent stress.     

Ovarian dynamics and fecundity regulation in blueback herring,Alosa aestivalis,from the Connecticut River,US

We analyzed ovarian dynamics of anadromous blueback herring, Alosa aestivalis, in Connecticut River with the principal aim of exploring oocyte recruitment and how it shapes the fecundity pattern. We examined the oocyte release strategy and analyzed spawning cyclicity by linking oocyte growth to the degeneration of postovulatory follicles. Females were accordingly classified as pre-spawners, early and late active spawners, and oocyte recruitment intensity was compared among the different spawning phases. Oocyte recruitment occurred continuously and in parallel with spawning activity, a pattern which is diagnostic of indeterminate fecundity. However, both fecundity and oocyte recruitment intensity progressively decreased (tapered) throughout spawning, until the ovary was depleted of vitellogenic oocytes. There was no massive atresia of vitellogenic oocytes at the end of the spawning season, which is atypical of indeterminate spawners. We propose that tapering in oocyte recruitment and fecundity is an adaptation to the high energetic expenditure of the upstream spawning migration.     

Timing and sites of parturition of the viviparous scorpionfish, Sebastiscus marmoratus

Timing and sites of parturition of the viviparous scorpionfish Sebastiscus marmoratus were investigated both in aquaria and natural habitats of a rocky coast in southern Japan. Females released 4 mm TL larvae during the early night in winter. Night spawning may be advantageous in avoiding predators of both larvae and spawners, because most such predators are inactive during the night. Females inhabiting shallow areas (< 6 m depth) moved to deeper sites for parturition, but ones inhabiting deeper areas (6–8 m depth) gave birth within their usual habitats. This migration may be advantageous in effective larval dispersal.     

Scale analysis suggests frequent skipping of the second reproductive season in Atlantic herring

A common assumption in fish studies is that iteroparous fishes, once mature, normally reproduce in all consecutive seasons. An analysis of scales from Norwegian spring-spawning herring collected between 1935 and 1973 revealed a strong under-representation (47% of expected) of second-time spawners on the spawning grounds. This reduction is not satisfactorily explained by errors in scale-reading, suggesting that the second reproductive season is frequently skipped. Skipping a season may relate to trade-offs between growth, current and future reproduction, and survival, which are likely to be particularly strong for young adult herring.     

Spawning migrations of the endemic Labeobarbus (Cyprinidae, Teleostei) species of Lake Tana, Ethiopia: status and threats

The reproductive biology of the only known intact species flock of large cyprinids, the 16 Labeobarbus species of Lake Tana (Ethiopia), has been extensively studied for the past two decades. Seven species of Labeobarbus are known to migrate >50 km upstream into tributary rivers for spawning during the rainy season (July to October), whereas eight other species are absent from these rivers and probably developed a new strategy of lacustrine spawning (macro-spatial segregation). One species (L. intermedius) probably spawns in the lake as well as in the rivers. Between the early 1990s and 2000s, the riverine spawners showed a decline of 75% in both biomass and number in both fishery independent surveys and in commercial catches. Reproductive migration makes fishes vulnerable to fisheries and other threats like habitat modifications. Lacustrine spawners are probably more resilient as they are not known to form spawning aggregations that can easily be exploited by fishermen. In addition, upstream rivers and catchments around Lake Tana are highly degraded by erosion and recently subjected to intensive habitat modification for irrigation and hydroelectric power generation. This article reviews results of field studies on the Labeobarbus spawning migration from Lake Tana to spawning rivers, giving emphasis on segregation and homing. It also summarizes existing and emerging threats which form potential causes for the decline of the migratory Labeobarbus species. Knowledge gaps on the reproductive biology are identified for further investigation.     

Recruitment prediction for Pacific herring (Clupea pallasi) on the west coast of Vancouver Island, Canada

The accurate prediction of recruitment to the fishery is a very important tool within the management structure of any fish stock being exploited. In the case of the Pacific herring, Clupea pallasi, fishery in Canada, a forecast of the abundance of each herring stock is particularly important for formulating an annual catch quota. The sustainable management of the fishery and the resource is based in part on accurate recruitment forecasting because Pacific herring are short-lived and so the recruitment contributes a significant part of the total spawning run targeted by the fishery each year. Several factors are believed be important in determining the success of recruitment besides spawners biomass. Since herrings are “r” strategists, conditions related to the egg, the planktonic, or even the juvenile stage might determine the future level of recruitment. Recently a formula that defines conditions for a semi-quantitative level of recruitment forecast was elaborated using genetic algorithms and current study attempts to improve on this model. Using salinity in two quarterly periods during the planktonic and pre-recruit stages, temperature and spawning biomass for the west coast of Vancouver Island stock, classification rules that define recruitment in 3 different levels (low, medium and high) were developed with a genetic algorithm, setting low and high boundaries for each condition. A 75% success in classifying recruitment was obtained. The model was shown to be particularly effective at predicting when the recruitment would be low, which could be important from the perspective of the Precautionary Approach and the sustainable management of this stock.     

Spawning frequency, fecundity, egg weight and spawning type of silver pomfret, Pampus argenteus (Euphrasen) (Stromateidae), in Kuwait waters

Silver pomfret, Pampus argenteus, were collected by fishing with drift gillnets on one spawning ground in Kuwait waters during 1998–2000. Fish size frequency, sex ratio, maturation cycle, spawning frequency, fecundity and egg weight were assessed. The length–weight relationship differed between sexes whereby females were significantly bigger than males. Spawning started in mid‐May and continued until early October. During this time the water temperature ranged from 26.0 to 32.8°C, salinity was ? 39.0‰ and water depth ranged between 5 and 12 m. Large females spawned earlier than young spawners and the overall percentage of males during the spawning period was 70.3%. Spawning occurred after 13.00 h, with peak spawning between 15.00 and 18.00 hours during outgoing tide. Mean daily spawning frequency amounted to 63.2%. Spawning activity was found to be associated with the lunar cycle and spawnings were concentrated during the first and third quarters of the moon period, indicating a semilunar reproduction cycle. It was concluded that a female would spawn at least six times during the season. No change was observed in relative fecundity during the peak spawning season (June–August). Average relative batch fecundity was 176.3 eggs g^?1 somatic weight (SW), corresponding to a relative total fecundity of 1058 eggs g^?1 SW, which is 1.5 times higher than estimates obtained from counting the standing stock of oocytes. Bigger fish produced heavier eggs and the egg weight decreased as the spawning season progressed. Based on gonadal cycles, oocyte size frequency distribution and total fecundity, we concluded that silver pomfret is a multiple batch spawner with indeterminate fecundity.     

Spawning ecology of Japanese surf smelt, Hypomesus pretiosus japonicus (Osmeridae), in Otsuchi Bay, northeastern Japan

The spawning habits of Japanese surf smelt, Hypomesus pretiosus japonicus (Japanese name chika), were studied from 1992 to 1995 at Akaiso Beach in Otsuchi Bay off the Pacific coast of northern Honshu. Investigations were conducted in relation to time, tidal rhythm, sand grain size on the spawning ground, and sex and age of spawners. Spawning occurred from late March to early May with its peak at the spring tide period during full moon in April. Before dark, fish gathered to school from 1–3 m depth, and 10–20 m off the shoreline of the spawning beach. Just before dark, they repeatedly approached the shoreline and stayed near the shoreline to spawn just after dark. In the spawning process, three intervals, i.e. aggregation, approach, and spawning, were recognized and these intervals are thought to be functionally connected. Mating occurred in a unit or group formed by one female and several males. During 1992–1995, except for 1994, spawning took place in a restricted region of the beach where backwash was stronger than other areas, and most sand grains were more than 1 mm in diameter and coarser than those of other areas. Although spawning was observed near the shoreline (34 to 120 cm tide level), most of the eggs were dispersed by backwash and each became attached to a few sand grains close to a step formed at 1–2 m depth off the spawning site. Spawners were composed mainly of age 0+ fish and some 1+ fish. Males usually outnumbered females on the spawning ground. Their spawning styles are discussed in relation to their ecology and habitat.     

Not a cakewalk: Insights into movement of large carnivores in human‐dominated landscapes in India

Large carnivores play an important role in the functioning of ecosystems, yet their conservation remains a massive challenge across the world. Owing to wide‐ranging habits, they encounter various anthropogenic pressures, affecting their movement in different landscape. Therefore, studying how large carnivores adapt their movement to dynamic landscape conditions is vital for management and conservation policy.A total of 26 individuals across 4 species of large carnivores of different sex and age classes (14 Panthera tigris, 3 Panthera pardus, 5 Cuon alpinus, and 4 Canis lupus pallipes) were GPS collared and monitored from 2014–19. We quantified movement parameters (step length and net squared displacement) of four large carnivores in and outside protected areas in India. We tested the effects of human pressures such as human density, road network, and landuse types on the movement of the species. We also examined the configuration of core areas as a strategy to subsist in a human‐dominated landscape using BBMM.Mean displacement of large carnivores varied from 99.35 m/hr for leopards to 637.7 m/hr for wolves. Tigers outside PAs exhibited higher displacement than tigers inside PAs. Moreover, displacement during day–night was significantly different for tigers inside and outside PAs. Similarly, wolf also showed significant difference between day‐night movement. However, no difference in day–night movement was found for leopard and dholes. Anthropogenic factors such as road length and proportion of agriculture within the home range of tigers outside PAs were found to be significantly different. All the habitat variables in the home range showed significant difference between the social canids. The core area size for tiger outside PA and wolf was found greater than PAs.The study on movement of large carnivore species across landscapes is crucial for conservation planning. Our findings can be a starting point for interlinking animal movement and landscape management of large carnivore conservation in the current Anthropocene.     

Comparison of fatty acid profiles of spawning and non-spawning Pacific herring, Clupea harengus pallasi

Crude lipid and fatty acid composition from liver, intestine, roe, milt and flesh of spawning and non-spawning Pacific herring (Clupea harengus pallasi) were examined to determine the relative effects of spawning on the nutritional value of herring. Depletion of lipid due to spawning condition was significant (P < 0.01) in all organ tissues and flesh of spawning herring. The lipid content ranged from an average of 1.9 to 3.4% (wet weight basis) in different organ tissues of spawning herring, to 10.5 to 16% in non-spawning fish. The fatty acid profile exhibited many differences in the relative distribution of individual fatty acids among organ tissues and between the two fish groups. Oleic acid (C18:1n-9), a major monounsaturated fatty acid (MUFA) found in all tissue lipids, decreased significantly (P < 0.01) in spawning fish. The two monoenes, C20:1n-9 and C22:1n-11, occurred at high concentrations in the flesh but at only minor proportion in the digestive organs and gonads. Spawning herring also had significantly (P < 0.01) higher polyunsaturated fatty acids (PUFA) content in the organ tissues, particularly in the milt and ovary, with docosahexaenoic acid (C22:6n-3, DHA) having the greatest proportion. Among the n-6 fatty acids, only C18:2n-6 and C20:4n-6 occurred at notable amounts and were present in higher proportions in spawning fish. We concluded that although relatively higher n-3 fatty acid content was found in the organ lipids of spawning herring, they are not an energy-dense prey food source due to the fact that both flesh and gonads contain a very low amount of lipid.     

Biogeochemical Signals from Deep Microbial Life in Terrestrial Crust

In contrast to the deep subseafloor biosphere, a volumetrically vast and stable habitat for microbial life in the terrestrial crust remains poorly explored. For the long-term sustainability of a crustal biome, high-energy fluxes derived from hydrothermal circulation and water radiolysis in uranium-enriched rocks are seemingly essential. However, the crustal habitability depending on a low supply of energy is unknown. We present multi-isotopic evidence of microbially mediated sulfate reduction in a granitic aquifer, a representative of the terrestrial crust habitat. Deep meteoric groundwater was collected from underground boreholes drilled into Cretaceous Toki granite (central Japan). A large sulfur isotopic fractionation of 20–60‰ diagnostic to microbial sulfate reduction is associated with the investigated groundwater containing sulfate below 0.2 mM. In contrast, a small carbon isotopic fractionation (<30‰) is not indicative of methanogenesis. Except for 2011, the concentrations of H₂ ranged mostly from 1 to 5 nM, which is also consistent with an aquifer where a terminal electron accepting process is dominantly controlled by ongoing sulfate reduction. High isotopic ratios of mantle-derived ³He relative to radiogenic ⁴He in groundwater and the flux of H₂ along adjacent faults suggest that, in addition to low concentrations of organic matter (<70 µM), H₂ from deeper sources might partly fuel metabolic activities. Our results demonstrate that the deep biosphere in the terrestrial crust is metabolically active and playing a crucial role in the formation of reducing groundwater even under low-energy fluxes.     

Comparative study of sexual cycles, oogenesis and spawning of two Soleidae, Solea lascaris (Risso, 1810) and Solea impar (Bennet, 1831), on the western coast of Brittany

Two sand sole species, Solea lascaris and Solea impar , are common on the western coast of Brittany, France. Their reproduction (oogenesis and spawning) has been studied by following the gonadosomatic index, histological changes in ovary development, and oocyte diameter distribution. Both species have a prolonged spawning season, from spring to late summer. Each mature female breeds twice during the spawning season: in May and July for 5. lascaris , and in early June and July for 5. impar. Throughout the spawning season, several oocyte batches undergo vitellogenesis and there is a continuous recruitment of immature or primary oocytes into vitellogenesis. The two species are thus serial synchronous spawners. This, together with oocyte atresia late in the season (especially noticeable in S. impar ) makes fecundity estimation difficult.     

Assessment of the Feasibility of Preventing Reproduction of Lake Charr, Salvelinus Namaycush, in Shallow Areas of Reservoirs Affected by Drawdowns

Lake charr, Salvelinus namaycush, spawn almost exclusively in lakes, in the fall. Spawning sites in inland lakes are generally located close to the shore in areas with coarse-textured substrate, and in depths of less than 2m. Because of the type of water management system applied in reservoirs where water levels are lowered during the winter, eggs deposited during the fall around the shallow shoreline of reservoirs can be exposed. The depth of spawning sites relative to drawdowns may be a limiting factor for lake charr survival in reservoirs. In 1995 and 1996, we evaluated the ability to induce lake charr reproduction in deeper water, below the range of fluctuating water levels by the sequential construction of artificial reefs and limiting access to natural spawning habitat. The creation of artificial deeper water spawning areas, adjacent to natural sites, produced a partial transfer of reproduction. However when natural spawning sites were covered with tarpaulins almost all the eggs were laid in the artificial deeper water spawning areas. Complete or partial transfer of reproduction activities to sites below the depth not affected by water level fluctuations is therefore a potential way of alleviating the effects of hydroelectric reservoir management.     

Salinity Responses of Benthic Microbial Communities in a Solar Saltern (Eilat, Israel)

The salinity responses of cyanobacteria, anoxygenic phototrophs, sulfate reducers, and methanogens from the laminated endoevaporitic community in the solar salterns of Eilat, Israel, were studied in situ with oxygen microelectrodes and in the laboratory in slurries. The optimum salinity for the sulfate reduction rate in sediment slurries was between 100 and 120‰, and sulfate reduction was strongly inhibited at an in situ salinity of 215‰. Nevertheless, sulfate reduction was an important respiratory process in the crust, and reoxidation of formed sulfide accounted for a major part of the oxygen budget. Methanogens were well adapted to the in situ salinity but contributed little to the anaerobic mineralization in the crust. In slurries with a salinity of 180‰ or less, methanogens were inhibited by increased activity of sulfate-reducing bacteria. Unicellular and filamentous cyanobacteria metabolized at near-optimum rates at the in situ salinity, whereas the optimum salinity for anoxygenic phototrophs was between 100 and 120‰.     

High Temperature and Salinity Enhance Soil Nitrogen Mineralization in a Tidal Freshwater Marsh

Soil nitrogen (N) mineralization in wetlands is sensitive to various environmental factors. To compare the effects of salinity and temperature on N mineralization, wetland soils from a tidal freshwater marsh locating in the Yellow River Delta was incubated over a 48-d anaerobic incubation period under four salinity concentrations (0, 10, 20 and 35‰) and four temperature levels (10, 20, 30 and 40°C). The results suggested that accumulated ammonium nitrogen (NH₄ ⁺-N) increased with increasing incubation time under all salinity concentrations. Higher temperatures and salinities significantly enhanced soil N mineralization except for a short-term (≈10 days) inhibiting effect found under 35‰ salinity. The incubation time, temperature, salinity and their interactions exhibited significant effects on N mineralization (P<0.001) except the interactive effect of salinity and temperature (P>0.05), while temperature exhibited the greatest effect (P<0.001). Meanwhile, N mineralization processes were simulated using both an effective accumulated temperature model and a one-pool model. Both models fit well with the simulation of soil N mineralization process in the coastal freshwater wetlands under a range of 30 to 40°C (R² = 0.88–0.99, P<0.01). Our results indicated that an enhanced NH₄ ⁺-N release with increasing temperature and salinity deriving from the projected global warming could have profound effects on nutrient cycling in coastal wetland ecosystems.