Fish Spawning Research Articles

Optimizing reservoir operation incorporating ecological demand and stability requirement

AbstractThe construction and operation of large‐scale reservoirs alter the natural river flow regimes and destroy the original suitable reproduction and living conditions of aquatic organisms. Especially during the spawning season, the fluctuating water flow process is particularly important for fish reproduction. A bi‐objective optimization model considering both the environmental flow demand for fish spawning and the stability of hydropower output is established in this study and solved by one of the most widely used algorithms for multi‐objective problems, the Non‐Dominated Sorted Genetic Algorithm‐II. The derived Pareto Front can be used to guide reservoir operation during fish spawning seasons. The model proposed in this paper is applied to the Yangqu Reservoir, currently under construction on the upper Yellow River in China. The results show that the stability of hydropower output can still be improved by 4.80% to 10.56%, even if the environmental flow demand is taken into account. Even for the scheme preferring ecological recovery, the stability of hydropower output can be increased by more than 0.85%.

The fishway of the Nikolaev waterworks on the Don river

The relevance of the study is determined by the reduction in stocks of populations of passable, semi-passable and aquatic fish species in the Azov-Don fishery basin. One of the reasons for this is a decrease (for various reasons and circumstances) in the efficiency of the functioning of fish-passing facilities located at the Don river waterworks, providing passage of fish to their spawning sites and, in particular, the Nikolaev fishway. The purpose of this study is to assess the current state and form proposals for the reconstruction of the canal. The methodology of the work provided for the analysis of the design solution, conducting a survey of the condition of the fishway of the Nikolaev waterwork and hydrometric changes in its flow-rate parameters. The empirical basis for the analysis and subsequent development of recommendations was made up of design materials and author’s data on fixing the hydrometric parameters of the channel. According to the results of the research, the main characteristics of the fishway, information on its layout and design solution are established, data on the flow-rate and geometric dimensions of the channel tract and the flow-regulating equipment are given, information on the established deformations of the channel bed in its various sections. The disadvantages of the layout and design solution of the device and the state of the channel have been established in terms of the lack of an engineering-equipped inlet (for fish) head, the adopted design of the head controller and the output section, as well as the selected hydrometric parameters of its tract. In order to eliminate a number of identified shortcomings that reduce the quality of hydrometric conditions for the passage and spawning of fish, it is proposed to reconstruct the structure. As a result of the formation of appropriate proposals (taking into account modern requirements and accumulated experience of their creation), recommended design solutions of the main elements of the channel have been developed, allowing to significantly increase the efficiency of its functioning in terms of attracting fish to its entrance, entry, spawning in its waters and passage through the fish channel to the abovelocated spawning grounds.

Phenology

Flowers blooming, fungi fruiting, insects biting, fish spawning, geese migrating, deer calving; our consciousness is steeped in a seasonal calendar of nature's events. Phenology is the study of these recurring, seasonal life-history events, though nowadays this term is widely applied to the events themselves. From Shakespeare's sonnet 98, "From you I have been absent in the spring", to the appearance of seasonal events and migratory species in the oral traditions of Native Americans, interest in phenology is long-standing and transcends cultures. In this primer we introduce the study of phenology, trace the development of the field, and examine the prominent role phenology has played in evidencing the widespread impacts of anthropogenic climate change on life on Earth. We will consider the potential implications of climatic change for the ability of populations to persist and the stability of species interactions.

Enhancing Reproductive Performance of Nilem Fish (Osteochilus hasselti) through Artificial Spawning

This study aims to evaluate the reproductive performance of Nilem fish (Osteochilus hasselti) through artificial spawning methods. Spawning was conducted in glass aquaria using the sGnRH-a hormone on both male and female broodstocks. Egg production, fertilization rate (FR), hatching rate (HR), and survival rate (SR) were the main observed parameters. The research results revealed that the average egg production per female broodstock reached 25,350, indicating a high level of fecundity. The fertilization rate reached 97.70%, indicating an effective egg fertilization process. The hatching rate (HR) value of 92.20% indicates success in the egg-hatching process. Larval survival rate (SR) during the 4-day rearing period reached 84.70%. Maintaining optimal water quality also contributed to the success of artificial spawning. In conclusion, artificial spawning in Nilem fish could achieve high levels of success by optimizing reproductive parameters and considering environmental factors. This study provides valuable insights into the sustainable development of Nilem fish cultivation.

Ichthyoplankton in the northern part of the Black Sea under prolongation of summer hydrological season in 2020

The species diversity and spatial distribution of ichthyoplankton in the shelf and deep-sea waters of the northern half of the Black Sea near the Crimean Peninsula and the shores of the Caucasus under the conditions of prolongation of the summer hydrological season 2020 for September–October are presented. The high temperatures of the upper layer of the sea, peculiar of the summer spawning season, caused a continuation of productive spawning of warm-water fish. Eggs and larvae of 19 species from 12 families were identified in the ichthyoplankton. The maximum number of eggs was 302 ind./m2, and larvae — 58 ind./m2. Eggs and larvae of the mass commercial species Engraulis encrasicolus (L., 1758) dominated, whose share in the total population was 92.9 and 84.2% respectively. The highest abundance of ichthyoplankton corresponded to areas with minimal dynamic activity and maximum warming within the limits of coastal-shelf quasi-stationary anticyclonic vortices characteristic of the summer hydrological season.

New insights into the role of myostatin in fish fertility based on the findings in mstnb-deficient Nile tilapia (Oreochromis niloticus)

Myostatin (Mstn) was reported to be involved in multiple biological processes including the regulation of skeletal muscle growth, lipid metabolism and reproduction in vertebrates, therefore, it might play an essential role in the fine balance between growth and reproduction. In order to clarify the roles of Mstn in fish reproduction, we systematically investigated the gonadal development and fertility of mstnb mutants in Nile tilapia (Orochromis niloticus). In the present study, mstnb was found to be expressed in the different cell types of gonads by fluorescence in situ hybridization (FISH). Mutation of mstnb resulted in excessive proliferation of phase II follicles in the ovaries while the numbers of phase III follicles were significantly reduced at 210 days after hatching (dah). Interestingly, significant decline of cyp19a1a gene expression, the serum 17β-estradiol (E2), vitellogenin (VTG) were detected at 210 dah. At 360 dah, the ovarian development of mstnb-/- XX tilapia was partially recovered and female fish spawn regularly, however, they were subfertile and produced the poor-quality eggs with significantly lower offspring survival rate. The dramatic up-regulation of cyp19a1a gene expression and serum E2 level at 360 dah might account for the recovery of ovarian development. In mstnb-/- males, excessive proliferation of spermatogonia and retardation of testicular differentiation were found throughout the whole development stages. In mstnb-/- males, evident declines of gonadosomatic index (GSI), cyp11b2 gene expression, and 11-Ketotestosterone (11-KT) were detected at 210 dah, while the mRNA level of cyp11b2 and serum 11-KT level were significantly upregulated at 360 dah. However, mstnb-/- males were infertile since mutation of mstnb gene led to excessive increase of apoptosis of testicular cells and spermiation obstacle. Taken together, these results indicated that Mstn might be an essential regulator for the maintenance of fish fertility.

Creating wetland islands to enhance shoreline habitat for fish recruitment in a modified shallow lake

Abstract Soft shoreline engineering is increasingly used to combine shoreline fortification with the enhancement of biodiversity and biological production of land–water transitions. From 2016 to 2021, the large‐scale ecosystem restoration project Marker Wadden has created new multiple wetland islands from local sediments in the highly modified Lake Markermeer, the Netherlands. Instead of replacing steep rip‐rap shorelines with soft shorelines, new islands with soft land–water transitions were engineered to offset the marked declines in bird and fish populations in this Natura 2000 area, protected under the European Union Birds and Habitats Directives. This new approach was evaluated by assessing the added value of the newly created wetland islands with soft shorelines to the existing steep rip‐rap fortified shores of the lake, for the enhancement of fish spawning and nursery habitat. Young‐of‐the‐year fish densities at the Marker Wadden islands were highest in sheltered bays and wetlands with nutrient‐rich silt sediments, and lowest at wind‐exposed sandy beaches. Both newly engineered soft shorelines and existing rip‐rap shorelines contributed to habitat diversity, although fish densities declined considerably with increasing exposure to wind‐induced wave power. Building soft shorelines as a new archipelago instead of replacing existing shoreline habitats increased the total length of the land–water transitions in the lake. The 800 ha Marker Wadden archipelago covers only 1% of the 70,000 ha lake surface area, but provides a 16% increase in shoreline habitat and a fivefold increase in soft shoreline for the lake. We conclude that designing wetland islands as a means of lake restoration can contribute effectively to sheltered habitat enhancement for fish spawning and nurseries, and thereby to the potential conservation of fish communities. The approach of building islands achieves this without compromising the complementary functionality of the original, more mature, shorelines of the lake.

A unified framework and terminology for reproductive traits integral to understanding fish population productivity

AbstractObjectiveThis paper highlights the complexity of marine fish spawner–recruit systems and how they vary across species and ecosystems while providing a universal terminology and framework to evaluate fish reproduction. We emphasize the gonadal development important to assess maturity, fecundity, where and when fish spawn, and transition and sex assignment in protogynous species.MethodsWe review and compare reproductive traits in warmwater and coldwater fishes. Reproductive phases for both sexes and protogynous species are defined and histological micrographs presented. New methods are developed to assess maturity; spawning seasonality; peak spawning; and, for protogynous species, sex assignment.ResultProtogyny, extended spawning seasons, and indeterminate fecundity are more common in warmwater than coldwater systems. The following reproductive phases are defined as immature, transitional (sex change), early developing (the first stage of entrainment in the reproductive cycle), late developing (stages needed to complete maturational competence), spawning, regressing (spawning season termination), and regenerating (fish that are mature but outside of the spawning season). A method to assess the certainty of maturity assignment based on reproductive phase and the age and size range sampled is presented, as are best practices to estimate size and age at maturity. To remove the subjectivity from current methods to estimate spawning seasonality, we present a new quantitative method to identify the core spawning season and peak spawning months.ConclusionA species’ ability to adapt to fishing and climate change varies with their reproductive strategy. Improving our understanding of fish reproduction necessitates standardizing methodology and terminology.

Perkembangan gonad, fekunditas dan diameter telur Hemisilurus heterorhynchus, Bleeker 1854 di sungai paparan banjir, Desa Mentulik, Kampar Kiri, Riau

Floodplain river is one of the freshwatercharacteristics of Riau Province. Selais humped fish (Hemisilurus heterorhynchus) is a demersal freshwater fish. and usually lives in tropical areas with rivers that are flood-prone. H. heterorhynchus is often caught regardless of size so that fish that are immature or have immature gonads are also caught. If this condition continues, it is likely that H. heterorhynchus will experience a population decline. Therefore it is necessary to conduct research on the reproductive biology of H. heterorhynchus to find out, gonadal development, gonado somaticindex (GSI), egg diameter, fecundity, the relationship between fecundity and body length and weight, spawning season and fish spawning patterns so that it can be used as a basis for conservation and cultivation of H. heterorhynchus. This research was conducted from October to March on the Kampar Kiri river. Gonad mature male and female fish were mostly found at the beginning of the rainy season in October and November. The highest male GSI was obtained in October (0.24%) and female in November (2.80%). Fecundity of H. heterorhynchus ranged from 6444-20654 eggs. The spawning pattern of H. heterorhynchus fish is once a year (total spawner).

Artificial reproduction of the sterlet (Acipenser ruthenus L., 1758) in Vologda region

The paper examines the preliminary results of measures taken for artificial reproduction of sterlet Acipenser ruthenus L., 1758 in Vologda region water reservoirs, carried out in 2014–2023. The authors calculate that for the formation of a significant commercial replenishment, it is necessary to annually release 170 thousand specimens into the Sukhona, Yug, Mologa rivers and the river part of the Sheksninsky Reservoir, and 50 thousand specimens of sterlet fingerlings with an average weight of 5 grams — into the Vaga River. The total release volumes over the ten-year period amounted to more than 2.7 million specimens, including 1.3 million into the Sukhona River, 534 thousand — into the Yug River, 455 thousand — into the Mologa River, 326 thousand — into the Sheksna Reservoir, and 89 thousand specimens — into the Vaga River. In research fishing with fixed nets in the Mologa River in 2018–2022, sterlet accounted for 42% of the total number and almost 50% of the biomass, in the Sukhona River in 2021–2022 — 18% and 25%, respectively, and in the river part of the Sheksninsky reservoir in 2020–2022 — 18% and 10%. The body length of the fish caught in the Mologa River varied between 20–51 cm, in the Sukhona River — 29–52 cm, in the Sheksninsky Reservoir — 16–37 cm, its weight was, respectively, 44–958 grams, 176–1278 grams and 22–336 grams. In the Mologa River and the Sheksninsky Reservoir, replenishment of populations is carried out only through artificial reproduction, and in the Sukhona River, natural spawning of fish has apparently also been preserved.

Optimization of selective withdrawal strategy in a warm monomictic reservoir based on thermal stratification

Selective withdrawal from reservoirs is an effective strategy for balancing economic goals and environmental demands. Multilevel intake operation (MIO) is one of the main options for improving the thermal regime of deep reservoirs. In this study, a combination of measured data and a two-dimensional hydrodynamic model (CE-QUAL-W2) was utilized to analyze the impact of MIO processes on the thermal stability of a reservoir and the improvement effect of the withdrawal water temperature (WWT). The purpose of this study was to identify an optimal selective withdrawal strategy to meet the water temperature needs of fish downstream during their spawning and breeding activities. The results showed that the MIOs raised the withdrawal water intake position (8.3–11.2 m) for the WWT. Meanwhile, MIOs resulted in statistically significant changes in the water temperature structure of the reservoir (p < 0.01). The stratification stability of the water column weakened (6.8 %-34.5 %), and there were interannual differences. The WWT increased by 0.0 °C∼1.9 °C every ten days, and the time to reach the optimum temperature (18 °C) for fish spawning was 7 to 17 days earlier. There was a statistically significant positive correlation between the WWT improvement and the stability index (SI) (R = 0.7817, p < 0.01). The threshold values of the SI (above the water intake) for average WWT improvements of 0.5 and 1.0 °C were 90.3 and 221.9 kg/m2, respectively, and the recommended operating period was from early-April to May. Under MIOs, the weakening stratification and the increasing WWT during the warming period reduced risks to the water quality and ecological health in the reservoir and downstream rivers. This study provides a helpful reference for the implementation of selective withdrawal operations and the optimization of water quality management strategies in similar large, deep reservoirs.

Changes in flow and sediment transport caused by cascade hydropower in the upper reaches of Yangtze River and their influence on spawning of Coreius heterodon

The upper reaches of the Yangtze River (YR) constitute the largest group of hydropower cascade projects in the world. The construction of cascade hydropower systems has a significant impact on the flow regimes and sediment transport in rivers, ultimately affecting fish spawning. Previous studies have examined the effects of fluctuating flow and water temperature on spawning; however, insufficient attention has been paid to their effects on sediment transport. This study analysed changes in runoff and sediment load (SL) at the Xiangjiaba hydrologic station (XJB) and Zhutuo hydrologic station (ZT) in the upper reaches of the YR over the past 60 years. Based on the indicators of hydrological regimes and sediment transport, we used the generalized additive models (GAM) to investigate the effects of cascade hydropower operations from 2009 to 2018 on the spawning abundance of Coreius heterodon (C. H) in the upper YR Fish Reserve. Following the operation of cascade hydropower, the SL and sediment concentration decreased by 56.8% and 56.6%, respectively, while the median size of the bed-material load demonstrated an initial thinning trend followed by subsequent coarsening. In addition, the frequency of the high-flow pulse increased by 32.1%, whereas the peak flow and duration of the high-flow pulse decreased by 41.2% and 62.6%, respectively. However, no significant changes were noted in the indicators of the flooding process. The decrease in sediment transport and changes in the flow regime led to a reduction in the spawning abundance of C. H. Reductions in sediment transport and changes in high-flow pulses caused by cascade hydropower can negatively affect C. H spawning, and SL is the most important indicator of impacts on spawning abundance (contribution of 77.7%). These findings are critical for evaluating the long-term impacts of cascade hydropower on fish habitats.

¿Where do migratory fish spawn in a neotropical Andean basin regulated by dams?

Spawning sites play a key role in the reproduction of fish allowing populations to endure over time. The Nechí River is an important spawning area for potamodromous fish species where one of the threats is dam construction. In order to determine the importance of the Nechí River as a spawning site in the Magdalena River basin, sampling was conducted during the low-water-to-high-water season transition period between 2018 and 2019 at seven sampling sites. The average density of ichthyoplankton was 42.4 ind.10m-3 (SD = 7.1). Of the individuals in the post-larval stage, seven migratory species were identified, and two additional taxa were identified to genus; Prochilodus magdalenae, Megaleporinus muyscorum, and Pseudoplatystoma magdaleniatum presented the greatest density. At the temporal level, the greatest density of larvae of potamodromous species was observed in the first high-water season of 2019 with a total of 5.7 ind.10m-3(SD = 1.044), of which the most representative at the seasonal level were the Cauca River, Magdalena River, and Nechí River before it flows into the Cauca River. There were significant differences in the frequency of embryos and vitelline larvae of the potamodromous species in the interaction of the sampling sites and high-water seasons, as well as with the density of post-larvae. The average drift distance of the spawning areas is roughly 52.1 km. A positive association was found between the volume of turbined water and the presence of ichthyoplankton in the Porce River site, after discharge from the Porce III Hydroelectric Plant. The Nechí River is an important spawning site and there seems to be an association between the increase in ichthyoplankton densities and the distance to the dam (Porce III) as long as there are floodplains along the course of the river.

Морфофизиологические и биохимические исследования каспийской атерины (Atherina boyeri caspia Risso, 1810)

The article highlights physiological and biochemical parameters of atherina (Atherina boyeri caspia Risso, 1810) in the Middle Caspian Sea at various stages of the annual cycle. The state of the fish organism was studied in the period from February to October 2022, which characterized the pre-spawning, spawning and feeding periods. The size-weight and age parameters of atherina were determined. The concentration of the main reserve substances of the fish body - total lipids and water-soluble protein – was analyzed in the muscles of the atherina. In the pre-spawning period and at the beginning of spawning of females, the level of morphological changes in the gonads was studied. There were no found significant differences in the content of total lipids and water-soluble protein in the muscles of males and females. Patterns of changes in the amount of muscle water-soluble proteins and total lipids were recorded in the entire sample of the Caspian atherina during the pre-spawning period and at the beginning of spawning. This is typical for portioned spawning fish, in which the energy expenditure of the body is directed to the formation, maturation of gonads, the removal of sexual products and the maturation of the next portions during the spawning period. In September-October, that is, already at the stage of feeding, a multidirectional character in lipid and protein metabolism was noted in the body of atherina. According to the results of histological examination, the beginning of spawning in atherina was noted in April. Mature oocytes with resorption at an average level of 30-31% were recorded in the ovaries of portioned spawning atherina in February-April, which characterized the adaptive mechanisms of the organism in the conditions of this habitat. In September, there was a significantly positive (p &lt; 0.05) statistical correlation between the concentration of total muscle lipids and the mass of fish (r = +0.47), which characterized a positive energy balance in the body, so necessary for the next stages of life.

Assessing larval fish diversity and conservation needs in the Luzon strait using DNA barcoding

IntroductionAccurate species identification and biodiversity assessment of larval fish are essential for effective management and conservation of fisheries resources, as it allows for the estimation of parent stocks, assessment of future recruitment, and prediction of spawning and nursing grounds. However, traditional morphology-based identification methods have inherent limitations, highlighting the need for accurate and efficient techniques to address these challenges effectively. The Luzon Strait, a crucial channel connecting the South China Sea to Western Pacific Ocean, is renowned for its fish biodiversity. However, our knowledge of the biodiversity status of larval fish species in this region remains insufficient.MethodsHere we employed DNA barcoding to assess larval fish species diversity in the Luzon Strait and adjacent waters. We investigated the species composition, diversity, and geographical distribution of larval fish communities in the region. Moreover, we assessed habitat types, human uses, and IUCN conservation status of each larval fish species.ResultsA total of 385 larval fish individuals were collected from 15 stations, and 354 individuals were successfully barcoded and identified, representing 147 species from 93 genera, 44 families, and 22 orders. The interspecific Kimura 2-parameter (K2P) divergence exhibited a significant increase of approximately 55-fold higher than intraspecific divergence. The phylogenetic neighbor-joining tree confirmed the distinct lineages for each taxonomic level, demonstrating the feasibility of DNA barcoding. We observed notable variations in fish species diversity and community composition among sampling stations. Non-metric multidimensional scaling analysis revealed greater diversity and dissimilarity of larval fish community compositions in the western regions compared to the eastern regions. This pattern corresponded to the grouping based on the path of the Kuroshio current, suggesting its influence on the fish community structure. Additionally, economically valuable species were identified at these stations, highlighting their ecological significance as potential spawning or nursery grounds for larval fish. We also examined the habitat type, human use, and conservation status of each larval fish species, providing comprehensive insights into their ecological significance and conservation needs.DiscussionThe establishment of a local DNA sequences database through DNA barcoding will greatly enhance the accuracy of species identification in environmental DNA (eDNA) metabarcoding applications. Altogether, this study offers valuable information for identifying important spawning and nursing grounds of fish populations, thereby supporting sustainable management and conservation of fisheries resources in this region.

Induced breeding of Sahyadria denisonii using different hormonal substances

Research on spawning stimulation of Sahyadria denisonii was carried out from June 2022 to October 2022 at the Research and Development Center for High-Tech Agriculture with three inducing agents, HCG, Ovaprim, and LHRHa + Domperidone. Each concentration of a hormone used in the experiment was applied on 5 pairs of brood fish. A 1 ml syringe was used for injecting to the anterior region of the dorsal fin by using a single-injection method and the injection timing of fish was 18 hours. Results showed that Ovaprim had an effect on inducing ovulation and laying eggs at a dose of 0.4-0.5 ml/kg of female fish. Female fish were exposed to hormones and ovulated after 11 hours 25 minutes to 11 hours 28 minutes from the time of injecting, 80% reproduction rate, actual fecundity from 747.67 to 750.33 eggs/female, 84% fertilisation rate, 84% hatching rate, time of embryo development was 30 hours at a water temperature of 29oC. The average length of new-hatched larvae was 3.2 mm with a large amount of yolk sac, the time to consume the yolk was from 3 to 4 days. HCG and LHRHa + Domperidonedid not have any effect on ovulation and spawning in fish.

Optimizing flow regime for the Four Major Chinese Carps by integrating habitat suitability within reservoir operation

The construction of dams has brought many benefits to human society. However, it has also altered the natural hydrological regime, affected aquatic organisms’ habitat conditions and decreased important fishery resources. In the post-dam construction era, it has become crucial to evaluate the ecological flow requirements for all stages of fish life and ensure the provision of dynamic flow pulsation, particularly during the spawning stage. Here, we proposed a Reservoir Operation Model for Fish Habitat across Life Stages (ROM-FHLS) to reconcile the apparent contradiction between fish habitat preservation and hydropower generation in the Yangtze River Basin. Compared with the conventional outflow conditions, our model demonstrated significant improvements in power generation and suitable habitat area during the migration, spawning and incubation, and juvenile periods. Specifically, we observed average increases of 15.2%, 13.1%, and 6.7% in power generation, and enhancements of 16.5%, 17.3%, and 1.8% in suitable habitat area, respectively. Our approach advocates for the comprehensive protection of fish throughout their entire life cycle while highlighting the feasibility of enhancing fish habitats without compromising power generation. Furthermore, we proposed an outflow scheme that incorporates pulsation patterns into reservoir operations to effectively stimulate fish spawning activities. This study presents a fresh perspective on comprehending the intricate interplay among dam-controlled hydrological processes, river hydrodynamic environment, and fish behavior. The findings have the potential to enhance fish spontaneous reproduction and aid in the recovery of aquatic populations in large dammed rivers.

Assemblage Structure of Ichthyoplankton and Its Relationship with Environmental Factors in Late Summer-Autumn and Winter in the Beibu Gulf, China

Being a biologically diversed hotspot in the global marine ecosystem, the Beibu Gulf is inhabited by a high diversity of fish and serves as a vital fishing ground in China. Due to continuous overfishing, the fishery resource has drastically declined in the Beibu Gulf. However, information about the ichthyoplankton assemblages in this area is still lacking. In this present study, ichthyoplankton diversity, spatial and temporal distribution patterns, and assemblage structures were examined using the specimens collected in the late summer–autumn and winter of 2022 in the Beibu Gulf, and the relationship between ichthyoplankton assemblage and environmental variables was studied. A total of 117 ichthyoplankton taxa, belonging to 13 orders and 42 families, were recorded. The most abundant families were Gerreidae, Leiognathidae, and Sillaginidae in late summer–autumn, accounting for 38.74%, 27.95%, and 9.94%, respectively. Sparidae, Platycephalidae, and Sillaginidae were the most abundant families in winter, accounting for 34.03%, 17.15%, and 8.20%, respectively. Cluster analysis identified five assemblages in late summer-autumn and four assemblages in winter. The most characteristic species in each cluster were Terapon jarbua, Sillago sihama, Leiognathus brevirostris, Mene maculate, and Scomberoides tol in late summer-autumn and Scomberomorus commerson, Acanthopagrus latus, Sillago sp., and Evynnis cardinalis in winter. The results of the canonical correspondence analysis indicated that pH, chlorophyll-a (Chl-a), depth, dissolved oxygen (DO), sea surface salinity (SSS), total nitrogen (TN), and total phosphorus (TP) were the major environmental variables affecting the ichthyoplankton assemblage structure in the Beibu Gulf. The finding of this study will provide valuable information in conserving fish spawning grounds and developing fishery management practices to protect fishery resources in the Beibu Gulf.

Natural or Reclaimed Coastal Areas? The Role of Environmental Awareness in Supporting Coastal Ecotourism within Fishing Communities

Visiting fishing villages and natural coastal areas offer unique experience for city dwellers. Sadly, many beautiful coastal areas in fast developing cities are witnessed to turn into new concrete jungles or man-made attractions through land reclamation. Land reclamation is the process of creating a new artificial land from the sea (Rosman et al., 2020). The construction of reclaiming lands from sea are known to destroy natural landscapes, damage natural areas for fish spawning and marine nursery habitats, lower the level of oxygen in the water, and significatly reduce the numbers of fish and other marine resources in the affected area (Ding et al., 2020; Xu et al., 2021). Land reclamation also may deprive fishermen and fishing communities of access and ability to utilize coastal and marine resources, thus directly affecting fishermen's income (Fabinyi, 2020). To sustain their livelihood and reduce their dependency on the declining marine resources, fishermen ventured into coastal ecotourism, providing tours and turning their fishing house into tourists accommodation (Stacey et al., 2021). According to Pineda et al. (2023), tourists who participates in ecotourism usually prefer going to natural areas, with the intention to help conserve the area and bring benefits to local communities. However, little is relatively known about how much tourists support fishing communities conducting ecotourism and whether environmental awareness does influece their support. Hence, this study investigates environmental awareness (EA) as a mediatior in influencing the perception of land reclamation negative impacts (LR) and support for coastal ecotourism within fishing communities (CE). Keywords: Coastal Ecotourism, Environmental Awareness, Fishing Community, Land reclamation

Identification, location and characterisation of spawning grounds and nurseries in the littoral zone of Lake Kivu (eastern DR Congo)

AbstractWorldwide biodiversity is on the brink of extinction following the complete disappearance of many forest and freshwater vertebrates. This disappearance is closely linked to the reduction and disturbance of habitats, which should instead benefit from special conservation. In the case of lake ecosystems, fish spawning grounds remain the most vulnerable. This study aims to identify, characterise and locate fish spawning and nursery sites in Lake Kivu for better conservation. Sixteen sampling sites were selected along the shoreline of the Bukavu sub‐basin. Physico‐chemical parameters were measured in situ, and fish were captured using multi‐mesh nets, identified and dissected, gonads observed and sexual maturity stages determined. Twenty‐five fish species were identified, but 17 of these use the selected sampling sites as spawning and/or nursery. Eleven spawning and nine nursery sites were identified and located. Physico‐chemical analyses showed that temperature (F = 2.124, p = 0.011), dissolved oxygen (F = 2.792, p &lt; 0.001), depth (F = 5.915, p &lt; 0.001) and transparency (F = 3.421, p = 0.004) were significantly different, which characterise each site and may be key factors in species distribution between spawning sites. Fish size–weight relationships indicate allometric growths. The results of this research contribute to empirical knowledge of fish spawning grounds.