scholarly journals Spatiotemporal Changes of the Environmental DNA Concentrations of Amphidromous Fish Plecoglossus altivelis altivelis in the Spawning Grounds in the Takatsu River, Western Japan

2021 ◽  
Vol 9 ◽  
Author(s):  
Ryutei Inui ◽  
Yoshihisa Akamatsu ◽  
Takanori Kono ◽  
Minoru Saito ◽  
Seiji Miyazono ◽  
...  
Keyword(s):  
Economic Value ◽  
Environmental Dna ◽  
Spawning Season ◽  
Spawning Ground ◽  
Plecoglossus Altivelis ◽  
Spawning Grounds ◽  
Real Time Quantitative Pcr ◽  
Frequency Of Use ◽  
Western Japan ◽  
Japanese Rivers

The Ayu Plecoglossus altivelis altivelis is an amphidromous fish that is not only the most important commercial fishery species in Japanese rivers but also has a high economic value in recreational fishing. However, the degradation of its spawning grounds has caused a decrease in its abundance. In this study, we used environmental DNA (eDNA) to monitor the Ayu in the Takatsu River in Japan to (1) identify the spawning season in three known spawning grounds, (2) clarify changes in the main spawning grounds during the spawning season, and (3) discover unknown spawning grounds. We collected 1 L of the surface river water at three known spawning grounds nine times in 2018 and seven times in 2019 in the lower reaches of the Takatsu River. We also collected samples from seven unknown sites in 2018. The water samples were filtered through glass fiber filters. Total eDNA was extracted from each filtered sample and a Real-time quantitative PCR was performed with the specific primers and probe for Ayu. The results of the eDNA analyses showed that (1) the spawning season was in November in 2018 and in September in 2019. (2) One site was used as a spawning ground in both the early and the late spawning season, depending on the year. At the second site, the frequency of use changed year by year. The third site was the main spawning ground in the middle to late spawning season every year. From these results, we elucidated that some spawning grounds are used regularly every year, while the use of others varies year by year. (3) In five of the seven unknown sites, the nighttime eDNA concentrations were high at least once during the four surveys, suggesting that these sites may have functioned as spawning grounds. In particular, one site could be an important new spawning ground.

scholarly journals Does construction in the spawning ground improve the riverbed conditions making it suitable for spawning of the Ryukyu-ayu Plecoglossus altivelis ryukyuensis?

2020 ◽  
Vol 67 (4) ◽  
pp. 493-501
Author(s):  
Satoshi Awata ◽  
Tetsuya Tsuruta ◽  
Shin-ichiro Abe ◽  
Toshihiko Yonezawa ◽  
Kei’ichiro Iguchi
Keyword(s):  
Spawning Ground ◽  
Plecoglossus Altivelis ◽  
Plecoglossus Altivelis Ryukyuensis

ASSESSMENT ON THE SEASONAL BIOMASS VARIATIONS OF RIVERINE ORGANISMS USING ENVIRONMENTAL DNA ANALYSIS IN THE TAKATSU RIVER, WESTERN JAPAN

2020 ◽  
Vol 76 (2) ◽  
pp. I_1303-I_1308
Author(s):  
Kanta KOBAYASHI ◽  
Minoru SAITO ◽  
Yoshihisa AKAMATSU ◽  
Ryutei INUI ◽  
Takanori KONO ◽  
...  
Keyword(s):  
Dna Analysis ◽  
Environmental Dna ◽  
Western Japan

scholarly journals Response to Environmental Factors of Spawning Ground in the Pearl River Estuary, China

2021 ◽  
Vol 9 (7) ◽  
pp. 763
Author(s):  
Dongliang Wang ◽  
Lijun Yao ◽  
Jing Yu ◽  
Pimao Chen ◽  
Ruirui Hu
Keyword(s):  
River Estuary ◽  
Pearl River Estuary ◽  
Sea Surface ◽  
Spatiotemporal Variability ◽  
Pearl River ◽  
Spawning Ground ◽  
Spawning Grounds ◽  
Chl A ◽  
The Pearl River Estuary ◽  
The Pearl River

Spawning grounds are important areas for fish survival and reproduction, and play a key role in the supplement of fishery resources. This study investigated environmental effects on the spatiotemporal variability of spawning ground in the Pearl River Estuary (PRE), China, using the generalized additive model (GAM), based on satellite remote sensing (sea surface temperature (SST), chlorophyll-a concentration (Chl-a), sea surface salinity (SSS), depth), and in situ observations. Results showed that 39.8% of the total variation in fish egg density was explained by these factors. Among them, the most important factor was SST, accounting for 14.3%, followed by Depth, SSS, and Chl-a, with contributions of 9.7%, 8.5%, and 7.3%, respectively. Spawning grounds in the PRE were mainly distributed in the waters with SST of 22 °C, depth of 30–50 m, SSS of 16–35 ‰, and Chl-a of 6–15 mg/m3. From spring to summer, the spawning ground moved from the outlet of the PRE to the east. The distribution of the spawning ground in the PRE was mainly affected by the Pearl River Plume (PRP), Guangdong Coastal Current (GCC), and monsoons in this area.

DECISION PRINCIPLES FOR ASCENT SUPPORTS IN BUILDING CONSTRUCTION

2014 ◽  
Vol 1 (1) ◽  
Author(s):  
Dieter Schlagbauer ◽  
Christian Hofstadler ◽  
Cornelia Ninaus
Keyword(s):  
Empirical Studies ◽  
Economic Value ◽  
Scale Up ◽  
Point Of View ◽  
Construction Sites ◽  
Economic Point ◽  
Current State ◽  
Frequency Of Use ◽  
A Site ◽  
Economic Comparison

Ladders are the ascent system most commonly used to scale up a building, due to the low initial costs compared to other ascent equipment. The insufficiency of this approach is shown in an economic comparison of ladders, stair towers, and scaffoldings with integrated ascent support. Based on empirical studies, cost data and the current state of scientific knowledge, the ascent support with the highest economic value can be determined by considering safety, cost, time, stress, physical stress and strain, and frequency of use. A survey evaluated vertical transport routes, the ascent systems ladders, stair towers, and scaffoldings with integrated ladders. The findings indicate that from an economic point of view, ladders should be used only on construction sites where less than 54 ascents were performed each day. This leads to the assumption that for typical construction sites, with at least 6 ascents per person per day and a site usage for a period longer than one week, the operation of ladders is uneconomical.

Spawning Dynamics of Golf of St. Lawrence Herring (Clupea harengus)

1989 ◽  
Vol 46 (12) ◽  
pp. 2085-2094 ◽  
Author(s):  
Timothy C. Lambert ◽  
Shoukry N. Messieh
Keyword(s):  
Stock Assessment ◽  
Sampling Procedure ◽  
Clupea Harengus ◽  
Spawning Season ◽  
Biological Information ◽  
Age Classes ◽  
Spawning Grounds

Mean day of arrival of spawning herring (Clupea harengus) in the Gulf of St. Lawrence was calculated for different length groups by region and season. During the spawning season of both spring and autumn groups, herring arrived and deposited eggs on spawning grounds in decreasing order of age and length. Spawning bed surveys at two locations confirmed batch depositions of eggs which were correlated with the presence of dominant age-classes within the spawning population. Due to limitations of the port sampling procedure for collection of biological information routinely used in herring stock assessment, some length groups were underrepresented. This could result in the underestimation of the abundance of recruiting year-classes.

scholarly journals Influence of Spawning Ground Dynamics on the Long-Term Abundance of Japanese Flying Squid (Todarodes pacificus) Winter Cohort

2021 ◽  
Vol 8 ◽  
Author(s):  
Yang Liu ◽  
Xinmei Xia ◽  
Yongjun Tian ◽  
Irene D. Alabia ◽  
Shuyang Ma ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Environmental Changes ◽  
Decadal Variability ◽  
Spawning Ground ◽  
Catch Per Unit Effort ◽  
Spawning Grounds ◽  
Species Response ◽  
Todarodes Pacificus ◽  
The Pacific ◽  
Squid Abundance

Japanese flying squid (Todarodes pacificus) is one of the most commercially important resources in the Pacific Ocean and its abundance is largely affected by environmental conditions. We examined the influence of environmental factors in potential spawning grounds of the winter cohort, approximated from Japanese and South Korean catch and catch per unit effort (CPUE) data of Japanese flying squid. Annual spawning ground dynamics were constructed using sea surface temperature (SST), submarine elevation and mean Kuroshio axis data from 1979 to 2018. Based on these information, we generated a suite of spawning ground indices including suitability SST-weighted area of potential spawning ground (SSWA), mean values (January–April) of suitable SST (MVSS), and the meridional position (MP) of SST isolines (18–24°C). Comparable interannual-decadal variability patterns were detected between the squid abundance and spawning ground indices, with abrupt shifts around 1990/1991 and in recent decades. In particular, the Pacific Decadal Oscillation is negatively correlated with spawning ground indices, suggesting its role in regulating the environmental dynamics in the area. Further, the gradient forest model underpinned the importance of SSWA, SSWA_Lag1 and MVSS_Lag1 on squid abundance. The CPUE is also shown to be a better abundance index than the annual catch in modeling the species’ response to environmental variability in its spawning grounds. Our findings suggest that it is imperative to pay more and timely attention to the relationship between the abundance of Japanese flying squid and environmental changes, especially under adverse environmental conditions.

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