scholarly journals Environmental Variables and Ecological Distribution of Ichthyofauna Assemblages in the Calabar River, Nigeria: Present and Future Prospects

2016 ◽  
Vol 74 (4) ◽  
pp. 159-171
Author(s):  
Andem Bassey Andem ◽  
Sunday Ben Ekanem ◽  
Esien Ene Oku
Keyword(s):  
Surface Water ◽  
Water Temperature ◽  
Environmental Variables ◽  
Fish Fauna ◽  
Dry Season ◽  
Fish Diversity ◽  
Surface Water Temperature ◽  
Future Prospects ◽  
Ecological Distribution ◽  
Wet Season

Abstract Studies on environmental variables and ecological distribution of ichthyofauna assemblages were conducted in the Calabar River. Surface water and ichthyofauna were sampled in order to provide baseline or reference data on the Calabar River at present as regard its future prospects. Seasonal variation shows significant differences in surface water temperature, pH, DO, BOD, conductivity, TDS and TSS between sampling stations and insignificant differences in heavy metals such as cadmium, chromium, iron and copper between sampling stations. Twenty six species of fish fauna were identified belonging to twenty two families. Mugilidae, Clariidae, Cichlidae, Gobiidae and Sciaenidae were the most abundant for both wet and dry season, while Clupeidae, Bathyclupeidae, Carangidae and Sphyraenidae were low in the wet season but high in the dry season. Chromium, copper, surface water temperature, DO correlate significantly with the presence of E. fimbriata, B. soporator, M. sebae, C. gariepinus, M. loennbergii, C. guentheri and P. babarus. The overall values of biotic diversity indices ranged from 0.0504-0.0745 for Simpson’s Index, 2.770-3.095 for Shannon Index, 2.821-3.105 for Margalef’s Index and 0.8606-0.9498 for equitability. However, the presence of certain fish fauna in polluted and non-polluted parts of the river indicates that they could be used as potential bioindicators in assessment and biomonitoring of the river. The methods used in identifying fish diversity proved their applicability for future studies.

scholarly journals Annual Pattern on Abundance and Sex Ratio Distribution of Selected Fish Fauna of Ikere Gorge Reservoir, Oyo State, Nigeria

2019 ◽  
Vol 9 (1) ◽  
pp. 1-13
Author(s):  
Festus Idowu Adeosun
Keyword(s):  
Sex Ratio ◽  
Fish Fauna ◽  
Diversity Indices ◽  
Fish Population ◽  
Dry Season ◽  
Fish Diversity ◽  
Wet Season ◽  
Ratio Distribution ◽  
Significant Difference ◽  
Catch Composition

Sex ratio affects the growth of wild population, thus, with the declining wild fish population, the study was designed to determine the effect of seasons on the sex ratio of fish population from Ikere Gorge, Nigeria for 18 months. Fish composition, diversity, distribution and abundance were determined according to standard methods. Sexes were determined and sex ratio was calculated using a standard method. A total of 5,823 fish specimens were caught during the period. The captured fish species were identified and classified into 34 species belonging to 13 families. The species richness was higher in the dry months than in the wet months. Fish diversity indices and evenness revealed a better diverse and even ecosystem in the wet season than the dry season. A marked significant difference (p < 0.05) was observed between the species in the dry months than the wet season. Chrysichthyes nigrodigitatus (35.07±7.59a) was significantly (p < 0.05) more abundant than the other species in the dry season. The sex ratio was skewed in favour of the female populations for C. nigrodigitatus, Tilapia melanopleura and Sarotherodon galilaeus but the reverse was the case for L. niloticus population. No monthly variation was observed in sex ratio of the species. The fish fauna from Ikere Gorge showed marked variations in the catch composition between the dry and wet months. C. nigrodigitatus and the Cichlids (Hemichromis fasciatus, S. galilaeus, Tilapia macrocephla and T. melanopleura) were present all year.

scholarly journals Surface Water Temperature Predictions at a Mid-Latitude Reservoir under Long-Term Climate Change Impacts Using a Deep Neural Network Coupled with a Transfer Learning Approach

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1109
Author(s):  
Nobuaki Kimura ◽  
Kei Ishida ◽  
Daichi Baba
Keyword(s):  
Climate Change ◽  
Surface Water ◽  
Water Temperature ◽  
Transfer Learning ◽  
Air Temperature ◽  
Climate Models ◽  
Temporal Variations ◽  
Training Data ◽  
Surface Water Temperature

Long-term climate change may strongly affect the aquatic environment in mid-latitude water resources. In particular, it can be demonstrated that temporal variations in surface water temperature in a reservoir have strong responses to air temperature. We adopted deep neural networks (DNNs) to understand the long-term relationships between air temperature and surface water temperature, because DNNs can easily deal with nonlinear data, including uncertainties, that are obtained in complicated climate and aquatic systems. In general, DNNs cannot appropriately predict unexperienced data (i.e., out-of-range training data), such as future water temperature. To improve this limitation, our idea is to introduce a transfer learning (TL) approach. The observed data were used to train a DNN-based model. Continuous data (i.e., air temperature) ranging over 150 years to pre-training to climate change, which were obtained from climate models and include a downscaling model, were used to predict past and future surface water temperatures in the reservoir. The results showed that the DNN-based model with the TL approach was able to approximately predict based on the difference between past and future air temperatures. The model suggested that the occurrences in the highest water temperature increased, and the occurrences in the lowest water temperature decreased in the future predictions.

Impact of climate warming on the surface water temperature of plateau lake

2021 ◽  
Author(s):  
Zongqi Peng ◽  
Jiaying Yang ◽  
Yi Luo ◽  
Kun Yang ◽  
Chunxue Shang
Keyword(s):  
Surface Water ◽  
Water Temperature ◽  
Climate Warming ◽  
Surface Water Temperature ◽  
Plateau Lake

scholarly journals Absence of Surface Water Temperature Trends in Lake Kinneret despite Present Atmospheric Warming: Comparisons with Dead Sea Trends

2021 ◽  
Vol 13 (17) ◽  
pp. 3461
Author(s):  
Pavel Kishcha ◽  
Boris Starobinets ◽  
Yury Lechinsky ◽  
Pinhas Alpert
Keyword(s):  
Surface Water ◽  
Water Temperature ◽  
Dead Sea ◽  
Lake Kinneret ◽  
Surface Water Temperature ◽  
Water Lake ◽  
Increasing Trend ◽  
Atmospheric Warming ◽  
Fresh Water Lake

This study was carried out using Moderate Resolution Imaging Spectroradiometer (MODIS) 1 km × 1 km resolution records on board Terra and Aqua satellites and in-situ measurements during the period (2003–2019). In spite of the presence of increasing atmospheric warming, in summer when evaporation is maximal, in fresh-water Lake Kinneret, satellite data revealed the absence of surface water temperature (SWT) trends. The absence of SWT trends in the presence of increasing atmospheric warming is an indication of the influence of increasing evaporation on SWT trends. The increasing water cooling, due to the above-mentioned increasing evaporation, compensated for increasing heating of surface water by regional atmospheric warming, resulting in the absence of SWT trends. In contrast to fresh-water Lake Kinneret, in the hypersaline Dead Sea, located ~100 km apart, MODIS records showed an increasing trend of 0.8 °C decade−1 in summer SWT during the same study period. The presence of increasing SWT trends in the presence of increasing atmospheric warming is an indication of the absence of steadily increasing evaporation in the Dead Sea. This is supported by a constant drop in Dead Sea water level at the rate of ~1 m/year from year to year during the last 25-year period (1995–2020). In summer, in contrast to satellite measurements, in-situ measurements of near-surface water temperature in Lake Kinneret showed an increasing trend of 0.7 °C  decade−1.

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