基于two-stage GAM的万泉河口爪哇拟虾虎鱼仔鱼对环境因子的响应OA

As a typical tropical estuarine ecosystem,the Wanquan River Estuary provides essential spawning and nursery habitats for various fish species.The complex habitat conditions and hydrological and hydrodynamic environment in this area have significantly influenced the distribution patterns of early fish resources.Among these,the Javanese goby(Pseudogobius javanicus)stands out as the dominant species in the larval fish community of the region.This species is particularly sensitive to environmental changes,making it a crucial bioindicator for assessing habitat quality.To elucidate the key driving factors behind the dynamics of Javanese goby larvae and understand their responses to environmental factors,a year-round monitoring study was conducted from May 2021 to April 2022.The study was conducted at seven sampling sites within the Wanquan River Estuary,which collectively represent four distinct habitat types.During the monitoring period,larval samples of P.javanicus were collected systematically,and nine environmental parameters were measured.The objective of this study was to comprehensively investigate both the temporal and spatial patterns of larval abundance,and to reveal the underlying environmental factors influencing these patterns.A two-stage generalized additive model(GAM)was constructed to accurately model the response of larvae to environmental conditions.This approach is particularly effective for dealing with zero-inflated data common in larval fish surveys,where many observations may record zero abundance due to absence of sampling points or times.The two-stage GAM partitions the modeling process into occurrence probability and conditional abundance stages,allowing for a more nuanced understanding of how environmental factors affect presence and quantity separately.The results of the present study demonstrate that the abundance of Javanese goby larvae exhibits pronounced seasonality and spatial heterogeneity.Specifically,larval abundance was significantly higher during the rainy season(June-August)than during the dry season.Furthermore,the highest larval densities were consistently observed along mangrove fringes and submerged macrophyte zones,indicating that these habitats serve as critical nursery grounds for the species.The spatial preference for these habitats underscores their ecological importance,as they provide essential shelter and feeding opportunities for early life stages.The first component of the two-stage GAM(GAM1),which analyzed the presence versus absence data,identified temperature,ammonia nitrogen concentration,dissolved oxygen levels,and chlorophyll-a concentration as the primary environmental factors influencing the probability of occurrence of Javanese goby larvae.This model explained a cumulative deviance of 77.6％with statistically significant results(P＜0.05),highlighting the strong effect of these variables on larval habitat suitability.High ammonia nitrogen levels and low dissolved oxygen typically indicate poor water quality and were inversely related to the probability of larval presence,whereas optimal temperature ranges and moderate chlorophyll-a concentrations favor its occurrence.The second component(GAM2),focusing on larval abundance conditional on presence,revealed that salinity,pH,temperature,and chlorophyll-a collectively governed the variation in larval density,with a cumulative deviance explanation of 77.3％(P＜0.05).Salinity emerged as a critical factor,with two optimal ranges identified:10-15 and 20-25,suggesting some flexibility in larval tolerance or site-dependent habitat conditions.The pH window of 7.2 to 7.6 further delineated favorable acidic-alkaline conditions for larval growth and survival.The optimal temperature fell within the 26-30 ℃ range,which is consistent with the species' tropical affinity.Chlorophyll-a levels below 10 μg/L corresponded with better larval abundance,likely reflecting balanced primary productivity that supports appropriate food web dynamics without leading to eutrophication stress.Collectively,the two-stage GAM approach effectively overcame the challenges posed by zero-inflated larval count data,enabling accurate and detailed elucidation of the complex relationships between larval fish and their environmental context.Identifying specific"environmental windows"for key factors provides actionable thresholds that can guide management and conservation efforts.Based on these findings,the study recommends prioritizing the protection of mangrove edge zones and submerged vegetation areas within the Wanquan River Estuary,given their role as core nursery habitats for the Javanese goby and potentially other estuarine fish species.Active ecological restoration initiatives and disturbance mitigation measures should be implemented in these sensitive habitats to maintain or enhance their quality.Moreover,heightened monitoring and regulation of ammonia nitrogen and chlorophyll-a concentrations,especially during the rainy season from June to August when larval abundance peaks,should be enforced to prevent deterioration in water quality.Additionally,the establishment of a seasonal fishing moratorium for the rainy season is recommended.Designating no-fishing zones during this critical period can reduce anthropogenic pressure on the early life stages of fish,thereby facilitating recruitment success and long-term population sustainability.