Functional response in coccinellid beetles (Coleoptera: Coccinellidae) is modified by prey-density experience

In the present study, we assessed functional response curves of two generalist coccinellid beetles (Coleoptera: Coccinellidae), specifically Menochilus sexmaculatus and Propylea dissecta, using fluctuating densities of aphid prey as a stimulus. In what may be the first such study, we investigated how the prey density experienced during the early larval development of these two predatory beetle species shaped the functional response curves of the late instar–larval and adult stages. The predators were switched from their rearing prey-density environments of scarce, optimal, or abundant prey to five testing density environments of extremely scarce, scarce, suboptimal, optimal, or abundant prey. The individuals of M. sexmaculatus that were reared on either scarce- and optimal- or abundant-prey densities exhibited type II functional response curves as both larvae and adults. However, individuals of P. dissecta that were reared on scarce- and abundant-prey densities displayed modified type II functional response curves as larvae and type II functional response curves as adults. In contrast, individuals of P. dissecta reared on the optimal-prey density displayed type II functional response curves as larvae and modified type II functional response curves as adults. The fourth-instar larvae and adult females of M. sexmaculatus and P. dissecta also exhibited highest prey consumption (T/Th) and shortest prey-handling time (Th) on the scarce-prey rearing density. Thus, under fluctuating-prey conditions, M. sexmaculatus is a better biological control agent of aphids than P. dissecta is.

Integrated rearing system proposal for Cantareus aspersus in experimental orchards: Growth models

An integrated rearing system for Cantareus aspersus under environmental conditions in an experimental orchard is proposed. In this study, the natural behaviour, circadian rhythms and suitable rearing conditions of the edible snail were optimised to produce homogeneous growth and low variability. The growth was standardised, and growth pattern fit was assessed with various models. One thousand fry were cultured in the orchard, and a random sample of 100 snails were measured weekly for 23 weeks. The rearing system had the following characteristics: snails and earthworms were included in the experimental rearing orchard; a homogeneous group of juvenile snails of the same age and size and high rearing density (500 snails/m2) was used; snails were fed with layers mash ad libitum; and mixed and fringes vegetation was planted in the orchard. A commercial size of 60% of snails was achieved in 21 weeks and 95% in 23 weeks. The different models showed a good fit, and the quadratic model obtained the best fit. This experimental snail orchard proposal can be extended to other areas, although it must be corrected according to different environmental conditions and fit to other species of interest. This experimental model could constitute a viable alternative to traditional models of animal experimentation with mammals, and given its high adaptability, it could be applied in different fields of science.

Participatory Qualitative Modeling to Assess the Sustainability of a Coastal Socio-Ecological System

Assessing the sustainability of socio-ecological systems requires understanding the interactions between numerous ecological, economic and social components. Models are often used to investigate how interactions shape system feedbacks and drive the complex dynamics at play in such systems. However, building these models is a non-trivial exercise, which often neglects stakeholder knowledge and perceptions. We adopted a participatory approach that relies on conducting workshops to engage stakeholders into the development of qualitative models of system feedback. This type of participatory qualitative modeling is well suited to address the complexity of socio-ecological systems in a holistic manner, identify key stakes and feedbacks, and predict responses to perturbations. We use this approach to investigate the factors that condition sustainability of the socio-ecological system associated with shellfish aquaculture in the Normand-Breton Gulf in France. Six region-specific workshops were organized with shellfish producers, managers and other stakeholders to identify and describe key components, interactions and pressures that contribute to overall socio-ecological dynamics. Differences and commonalities in system perceptions were identified across the different regions and focus groups. We reconciled stakeholder-specific discrepancies in model structure into a synthetic representation that conciliates alternative views of the system. Next, we predicted how the system might respond to alternative scenarios of change. Overall, our participatory qualitative modeling exercise identified key drivers of the system under study that constitute effective management levers to maintain system sustainability. For instance, low social acceptability of the aquaculture industry generally appears to be a major constraint on the sustainability of shellfish aquaculture in the Normand-Breton Gulf, while reducing rearing density appears to be a key driver of sustainability.

Effects of food and rearing density of hybrid grouper (♂ \(\textit{E. lanceolatus}\) x ♀ \(\textit{E. fuscoguttatus}\)) from fry stage to fingerling

The study on the effects of food and rearing density of hybrid grouper (♂ E. lanceolatus × ♀ E. fuscoguttatus) from fry stage to fingerling was conducted at Nha Trang Mariculture Research and Development Center (Research Institute for Aquaculture No. 3) from March to May 2018 to assess the effects of live food and fish rearing density on the survival rate, the growth in length, the level of coefficient CVL and deformative rate. The study showed that feeding rotifers were better than the oyster larvae food, or the combination of rotifers and oyster larvae when used as food for the hybrid grouper at the fry stage to fingerlings with the survival rate at 5.4 ± 0.3%, specific growth rate at 7,90 ± 0,05% body length/day and the deformative ratio at 0.9 ± 0.3% (p < 0.05). Meanwhile, the rearing density of 8 fish/L to 12 fish/L of rearing water was recorded to be better than the density of 16 fish/L (p < 0.05).

Improvement of water quality for mass anopheline rearing: evaluation of the impact of ammonia-capturing zeolite on larval development and adult phenotypic quality

Background Malaria vector control approaches that rely on mosquito releases such as the sterile insect technique (SIT) and suppression or replacement strategies relying on genetically modified mosquitoes (GMM) depend on effective mass production of Anopheles mosquitoes. Anophelines typically require relatively clean larval rearing water, and water management techniques that minimise toxic ammonia are key to achieving optimal rearing conditions in small and large rearing facilities. Zeolites are extensively used in closed-system fish aquaculture to improve water quality and reduce water consumption, thanks to their selective adsorption of ammonia and toxic heavy metals. The many advantages of zeolites include low cost, abundance in many parts of the world and environmental friendliness. However, so far, their potential benefit for mosquito rearing has not been evaluated. Methods This study evaluated the independent effects of zeolite and daily water changes (to simulate a continuous flow system) on the rearing of An. coluzzii under two feed regimes (powder and slurry feed) and larval densities (200 and 400 larvae per tray). The duration of larval development, adult emergence success and phenotypic quality (body size) were recorded to assess the impact of water treatments on mosquito numbers, phenotypic quality and identification of optimal feeding regimes and larval density for the use of zeolite. Results Overall, mosquito emergence, duration of development and adult phenotypic quality were significantly better in treatments with daily water changes. In treatments without daily water changes, zeolite significantly improved water quality at the lower larval rearing density, resulting in higher mosquito emergence and shorter development time. At the lower larval rearing density, the adult phenotypic quality did not significantly differ between zeolite treatment without water changes and those with daily changes. Conclusions These results suggest that treating rearing water with zeolite can improve mosquito production in smaller facilities. Zeolite could also offer cost-effective and environmentally friendly solutions for water recycling management systems in larger production facilities. Further studies are needed to optimise and assess the costs and benefits of such applications to Anopheles gambiae (s.l.) mosquito-rearing programmes. Graphic abstract

REARING DENSITY IN THE PERFORMANCE AND PROFITABILITY OF ROSS 308 BROILERS

The objective was to evaluate the effect of stocking density on productive performance, carcass characteristics, productivity, bone development, and profitability of Ross 308 broilers. A completely randomized experimental design with four stocking densities (10, 12, 14, and 16 birds m-2) and four replicates, and the subplots the bone collection ages (7, 14, 21, 28, 35, and 42 days old). The variables analyzed were live weight at 21 and 42 days, weight gain, feed intake, and conversion in the accumulated periods from 1 to 21 and 1 to 42 days. Weights of carcasses, commercial cuts, edible viscera, abdominal fat, productivity, production efficiency index, viability, and profitability were evaluated. The length, thickness, weight, and Seedor index of long bones (tibiotarsus and femur) were also evaluated. The yield was higher for densities of 14 and 16 birds m-2. The thickness of the tibiotarsus was lower in the density of 12 birds m-2. The increase in the stocking density of 10 or 12 birds m-2, to 14 birds m-2 allows greater productivity per area, without compromising the productive performance, such as carcass characteristics and the animal's bone development, besides being the breeding density with the highest profitability, considering the welfare of Ross 308 broilers.

Production performance of white shrimp Litopenaeus vannamei with super-intensive culture on different rearing densities

This research aimed to evaluate the production performance of white shrimp Litopenaeus vannamei with super-intensive culture on different rearing densities. The research was conducted at PT. Dewi Laut Aquaculture, Cikelet, Garut, West Java. As many of 8 ponds were used and divided into 2 groups based on the stock density of shrimp, 550 ind/m2 and 650 ind/m2, and reared for 99 days. The results showed that super-intensive shrimp culture at the density of 550–650 ind/m2 potentially produced shrimp with average body weight ranged from 15.91–19.31 g, survival rate 62.67–87.95%, growth 0.16 to 0.20 g/day, FCR 1.35–1.66, and productivity reach 5.55–9.19 kg/m2. There were no significant differences between the two stocking densities in body weight, growth, and feed conversion performance, while ponds with higher rearing density had better survival and productivity than ponds with lower rearing density. L. vannamei cultured at a density of 650 ind/m2 produces the best performance and most feasible to be applied in super-intensive white shrimp cultivation. Keywords: Litopenaeus vannamei, super-intensive, high-density, production performance ABSTRAK Penelitian ini bertujuan untuk mengevaluasi kinerja produksi udang vaname pada sistem super- intensif dengan padat penebaran berbeda. Penelitian dilaksanakan di tambak PT. Dewi Laut Aquaculture, Cikelet, Garut, Jawa Barat, menggunakan 8 petak tambak. Tambak dibagi menjadi 2 kelompok, masing-masing 4 petak tambak dengan padat tebar udang 550 ekor/m2 dan 4 petak tambak lainnya dengan padat tebar 650 ekor/m2 dengan masa pemeliharaan 99 hari. Hasil penelitian menunjukkan bahwa budidaya udang vaname pada sistem super-intensif dengan padat tebar 550–650 ekor/m2 dapat menghasilkan udang dengan bobot rata-rata berkisar antara 15.91–19.31 g, sintasan 62.67–87.95%, pertumbuhan 0.16–0.20 g/hari, konversi pakan (FCR) 1.35–1.66, dan produktivitas mencapai 5.55–9.19 kg/m2. Tidak ada perbedaan nyata antara kedua padat penebaran pada kinerja bobot, pertumbuhan harian, dan FCR; sementara tambak dengan kepadatan tinggi memiliki nilai sintasan dan produktivitas yang lebih tinggi dari tambak dengan kepadatan rendah. Padat penebaran 650 ekor/m2 menghasilkan kinerja produksi terbaik dan paling layak untuk diaplikasikan dalam budidaya udang vaname super-intensif. Kata kunci : Litopenaeus vannamei, padat tebar tinggi, super-intensif, kinerja produksi

Compensatory growth response of Catla catla (Hamilton, 1822) juveniles, stunted with varied stocking density and photoperiod, in subsequent grow-out phase

Stunted juveniles of Catla catla (Hamilton, 1822) were produced through 150 days of stunting with five combinations of density and photoperiod. These stunted juveniles were subsequently polycultured in grow-out ponds for eight months along with rohu (Labeo rohita) and mrigal (Cirrhinus mrigala). In grow-out trial, the five treatments with different combinations of stocking density and photoperiod comprised, control (20 m-3, 12L/12D), T-1 (30 m-3, 12L/12D), T-2 (40 m-3, 12L/12D), T-3 (20 m-3, 6L/18D) and T-4 (20 m-3, 0L/24D). After eight months of culture, growth curves of stunted catla in all treatments were non-convergent and inferior to control, indicating no compensatory growth response. Although survival (70-73%), average body weight, (ABW; 667-755 g) and weight gain (648-729 g) in grow-out phase were statistically similar in the groups with different stocking density (Control, T-1 and T-2) (p>0.05), the grow-out survival was relatively higher in T-2 (73.3%), indicating its positive correlation with higher stunting density. In contrast, juveniles stunted with reduced photoperiod (T-3 and T-4) showed significantly lower ABW and weight gain (p<0.05). The poor survival in T-3 and T-4 (40-43%) indicated significant effect of stunting with reduced photoperiod on subsequent grow-out survival and yield performance. Based on the results, the study recommend the use of rearing density up to 40 m-3 for juvenile stunting in catla.