ABSTRACT
Based on samples collected by bottom trawl in May, August, November and December 2016 in the Minjiang Estuary, species richness and functional diversity of fishes, as well as their spatial-temporal variations, were quantified by a trait-based approach. The functional diversity varied with the changes of species richness. The species richness averaged across all stations were (17.8±5.1) species in spring, (22.4±5.6) in summer, (17.7±6.3) in autumn, and (12.1±2.3) in winter. Functional diversity also showed seasonal variation, with the highest in summer as (33.94±28.70), followed by (9.93±8.83) in winter, (11.30±7.55) in spring and (19.05±19.32) in autumn. The key functional species varied seasonally, as Setipinna taty contributing to 26% of the total functional value in spring, Polydactylus sextarius at 26% in summer, Harpadon nehereus climbing to 69% in autumn, and Collichthys lucidus at 38% in winter. The seasonal variations of fish species function were determined by life history and its interaction with other species.
Subject(s)
Estuaries , Perciformes , Animals , China , Fishes , SeasonsABSTRACT
Based on the seasonal bottom trawl surveys in the Minjiang River Estuary in 2015, the breadth and overlap of ecological niche of major fish species were analyzed. Those fish species were identified based on the index of relative importance (IRI). A total of 137 species belonging to 37 families and 16 orders were collected. Fifteen major fish species were determined by the IRI, including six dominant species Polydactylus sextarius, Harpadon nehereus, Pennahia argentata, Secutor ruconius, Cynoglossus abbreviates, Coilia mystus, and nine important species Collichthys lucidus, Amblychaeturichthys hexanema, Upeneus japonicas, Lagocephalus spadiceus, Pampus argenteus, Larimichthys crocea, Thryssa kammalensis, Takifugu oblongus, Lepturacanthus savala. Seven species whose spatio-temporal niche breadth was higher than 1 in a declining order were C. abbreviates, C. lucidus, S. ruconius, A. hexanema, T. kammalensis, C. mystus, H. nehereus. The ecological niche of major fish species in the Minjiang River Estuary showed obvious seasonal dynamics. The percentage of species pairs with spatio-temporal niche overlap at the meaningful level was as high as 81.9%. Six species pairs reached significant ecological niche overlap, indicating that major fish species had similar distribution at the spatial and temporal scales and the existence of resource utilization competition. The species pairs of U. japonicus-L. savalawas had the highest spatio-temporal niche overlap value, whereas U. japonicus-C. lucidus had the lowest niche overlap value. The spatio-temporal niche overlap of major fish species in the Minjiang River Estuary had substantial seasonal variation.
Subject(s)
Estuaries , Fishes/physiology , Rivers , Animals , China , EcosystemABSTRACT
To study the trophic structure of fish community in Minjiang Estuary, we measured the carbon and nitrogen stable isotope ratios (δ13C and δ15N) of common fish species sampled in winter (January), spring (May), summer (August) and autumn (November) of 2015 by trawling, as well as seven quantitative metrics (ratios range of δ15N, NR; ratios range of δ13C, CR; total area, TA; standard ellipse area, SEAc; average distance of centroid, CD; mean nearest neighbor distance, MNND; standard deviation of nearest neighbor distance, SDNND). The results showed significant differences of δ13C values among all the seasons except between summer and autumn. There were significant differences of δ15N values between spring and other three seasons but no significant difference among summer, autumn, and winter. According to the results of the seven quantitative metrics, trophic structure of common fish community remarkably varied among the four seasons, as TA, SEAc, CR, NR, CD and MNND increased in succession from summer, autumn, winter to spring. Our results indicated that seasonal differences in trophic structure of common fish community were related to the fish spawning migration and the diversity of food source.
