Present research suggests that phenotypic variations and consequent potential differences in suitability for commercial culture are more likely to occur among genetically diverse populations. We investigated diversity in traits important to aquaculture and assessed genetic differentiation based on four mitochondrial markers in three European populations of Perca fluviatilis. Using a transplant approach to standardize conditions and minimize environmental effects on phenotype expression, we compared survival, cannibalism, growth rate, growth heterogeneity, and specific growth rate of the populations to assess whether difference in aquaculture performance (i.e. expression of phenotypical traits that facilitate the rearing of fish and impact the productivity of the farming) is more likely between genetically differentiated populations than between genetically similar populations. We found key traits of performance to differ among allopatric populations, suggesting value in considering geographic source of broodstock. The largest aquaculture performance disparities were observed among genetically differentiated populations. Some lesser differences were observed between allopatric genetically similar populations, possibly the consequence of pre-collection environment, or transgenerational effects.

Manuring and supplementary feeding are common practices used to sustain high fish production in temperate semi-intensive carp ponds. How ever, the low use efficiency of added nutrients and organic matter may cause carp ponds to be 'hot spots' of methane (CH 4 ) production and emission. Surface CH 4 concentrations were measured and diffusive CH 4 flux was estimated using a wind-based transboundary layer model in 3 nursery and 3 main carp ponds with different feeding rates and organic loading during 1 growing season. Mean (± SD) concentrations of CH 4 were 1.3 ± 0.9 µM and 0.8 ± 0.8 µM in nursery and main ponds, respectively. All ponds were sources of CH 4 , with diffusive CH 4 fluxes of 9.1 ± 6.8 mg C m −2 d −1 in nursery ponds and 6.4 ± 6.9 mg C m −2 d −1 in main ponds. Lower CH 4 concentration and diffusive flux in the main ponds were probably due to bioturbation caused by the larger carp and consequent oxidation of the sediment. Seasonal dynamics of CH 4 were mainly related to temperature. Methane concentration and diffusive flux levels re corded in this study were within the range of those reported in natural water bodies worldwide. Our results provide information on the role of carp aquaculture in greenhouse gas emission in temperate regions.KEY WORDS: Methane · Greenhouse gas emission · Aquaculture pond · Freshwater · Seasonality · Temperature Emission of diffusive methane from a temperate fishpond and inputs inducing CH 4 production in carp ponds: (A) manuring and (B) feeding.Photo credit: Dr.

Pre-service science and mathematics teachers’ beliefs and attitudes concerning technology integration significantly influence how confident they are to integrate technology into their teaching. This study is a comparative examination of the technological pedagogical content knowledge (TPACK) self-efficacy of 202 pre-service science and mathematics teachers enrolled at two Zambian universities. It also investigated the influence of selected demographic variables on the TPACK self-efficacy of pre-service science and mathematics teachers. The study employed a cross-sectional survey research design to collect data, which was analyzed using the independent samples t-test and one-way ANOVA. The findings reveal that pre-service teachers have moderate TPACK self-efficacy. Furthermore, the results indicate that students’ self-efficacy at the two universities was not statistically different (t[200]=2.11, p=.83); nonetheless, their TPACK self-efficacy was influenced by gender, year of study and subject specialization in some TPACK constructs. The implications of these findings were discussed.

Background: Wild fish populations stock is continuously diminishing in the Indo-Ganges river basin, and the population status of most fishes is unidentified. The identification of the population status and the conservation of commercially important and endemic wild fish populations in this region are crucial for the management. The aim of this paper was to identify the population status of Cirrhinus reba, a promising aquaculture but vulnerable species in the Indo-Ganges river basin in Bangladesh. Methods: C. reba samples were collected from four isolated populations of the Brahmaputra (n = 30), the Padma (33), the Karatoya (31), and the Jamuna Rivers (30) in Bangladesh, and the population status was evaluated using morphometric and landmark comparisons. Data were analyzed with the Kruskal-Wallis test, univariate analysis, discriminant function analysis, and the formation of a dendrogram. Results: Three meristic characters (Pectoral fin rays, caudal fin rays, scale in lateral lines), four morphometric characters (head length, pre-orbital length, post-orbital length, maximum body depth), and truss measurement (4-7) were significantly different among the stocks. The step-wise discriminant function analysis retained 15 variables from morphometric and landmark measurements that significantly differentiated the populations based on the constructed DFI and DFII. Discriminate function analysis also showed that 91.2% of the original groups were classified into their correct samples. The cluster analysis of Euclidean distances placed the Jamuna population in one cluster and the Brahmaputra, the Padma, and the Karatoya populations in the second one. Conclusion : Morphological differences among the stock were probably due to different ancestral origin. This is the first report about population status of C. reba in their natural habitat of the Indian subcontinent. Further genetic studies and the evaluation of environmental impact on C. reba populations in Bangladesh are suggested to support our findings.

Eutrophication and nutrient pollution is a serious problem in many fish aquaculture ponds, whose causes are often not well documented. The efficiency of using inputs for fish production in a hypereutrophic fishpond (Dehtář), was evaluated using organic carbon (OC), nitrogen (N) and phosphorus (P) balances and measurement of ecosystem metabolism rates in 2015. Primary production and feeds were the main inputs of OC and contributed 82% and 13% to the total OC input, respectively. Feeds and manure were the major inputs of nutrients and contributed 73% and 86% of the total inputs of N and P, respectively. Ecosystem respiration, accumulation in water and accumulation in sediment were the main fates of OC, N and P, respectively. They accounted for 79%, 52% and 61% of OC, N and P inputs. The efficiency of using OC, N and P inputs to produce fish biomass was very low and represented 0.9%, 25% and 23% of total OC, N, and P inputs, indicating an excessive phytoplankton production and overdosing of fish feeds and manure. Dehtář pond was slightly autotrophic and phosphorus availability did not limit the phytoplankton growth. The low efficiency of using inputs was attributed to the low digestibility of raw cereals grain used as feed and the inability of planktonic food webs to transfer the primary production to fish due to high predatory pressure of fish stock on zooplankton. The primary production is an important input of OC in semi-intensive fishponds and should be considered in evaluations of fish production efficiency.