Nutritional value of Pavlova spp. (Prymnesiophyceae) for spat of the Cortez oyster Crassostrea corteziensis during late-nursery culturing at the hatchery

Three Pavlova species were evaluated for their nutritional value as diets for growth and survival of the Cortez oyster Crassostrea corteziensis spat during late‐nursery cultivation at a hatchery. Microalgae were provided as monospecific diets (Pavlova salina, P. sp. C50 and P. sp. C53) and in binary combinations of diets 1+2, 1+3 and 2+3 at 80–90 × 10³ cells mL^?1 for 21 days. Juveniles experienced high survival rates and grew well with all dietary treatments, but binary diets yielded greater survival and growth of spat. From the three binary treatments, Diet 6 (P. sp. C50 and P. sp. C53) promoted significantly (P<0.001) fastest growth of juveniles in shell height (0.19 mm day^?1), shell length (0.14 mm day^?1), total wet weight (0.04 g day^?1) and dry weight of meat biomass (0.024 g day^?1). For all shell dimensions, the lowest growth rates occurred with Diets 2 (P. sp. C56 alone) and 3 (P. sp. C50 alone). These results highlight the importance of testing microalgal diets for bivalve spat rather than just relying on published nutritional values.     

Effects of live prey availability on growth and survival in the early stages of cuttlefish Sepia officinalis (Linnaeus, 1758) life cycle

This investigation examined the effects of live prey availability on growth and survival of Sepia officinalis. Two independent experiments, comprising two feed rations each, were performed, using adequate prey size. In the first experiment, cuttlefish hatchlings were fed live mysids, Paramysis nouvelli [(feed ratio I (fr I)], at 15% body weight per day (bw day^?1) (fr I₁₅) and 30% bw day^?1 (fr I₃₀). In the second experiment, juvenile cuttlefish were fed live Atlantic ditch shrimp, Paleomonetes varians (fr II), under the same experimental design. In both experiments, the final mean weight, feeding rate and instantaneous growth rate were higher when animals were fed feed ratio fr II₁₅ and fr II₃₀ (30% bw day^?1). The results indicate that prey availability influenced weight gain, irrespective of the prey used, during the first 2 months of cuttlefish life cycle. This effect seems to be more noticeable when a certain limit of prey is achieved. For cuttlefish fed fr II, the optimal prey density is thought to be under 2.5 g prey L^?1 (i.e. 14 shrimp L^?1). Results indicate that cuttlefish can withstand prey densities up to 120 mysids L^?1 for cuttlefish up to 3 weeks old and 19 shrimps L^?1 for cuttlefish up to 6 weeks old.     

Effects of density on growth and survival of juvenile Red Swamp Crayfish, Procambarus clarkii (Girard), reared under laboratory conditions

The aim of this study was to quantify the importance of population density on the growth and survival of juvenile red swamp crayfish, Procambarus clarkii (Girard), and to understand the effects of density on both the period between moults and the increment per moult at high densities without food limitation. A laboratory experiment was performed to determine growth and survival of juvenile crayfish at five densities (20, 40, 60, 80 and 100 crayfish m^?2). Density clearly affected crayfish growth. The impact of density on final weight was higher than on total length increase, growth rate and final length (FL) (by decreasing order of effect). When comparing minimum and maximum densities, we observed that FL suffered a 34% reduction. Number of moults, mean intermoult period (IP) and survival were not significantly affected by density. Our results indicated that the IP and the percentage of increment per moult are affected by the size of crayfish before moult and we provide equations for these relations. Our findings are relevant both for crayfish aquaculture management and for the management of wild or harvested rice‐field crayfish populations.     

Trawling for cephalopods off the Portuguese coast—Fleet dynamics and landings composition

Fleet dynamics was addressed for three cephalopod taxa of commercial interest, the squid Loligo vulgaris, the octopuses Octopus vulgaris and Eledone cirrhosa, and the cuttlefish Sepia officinalis, for 48 trawlers of the fish trawling fleet. Landing profiles (LP) were identified based on the species composition of the landings using hierarchical cluster analysis. Four out of a total of 12 different LP were related to cephalopods and other species associated with them.The effects on the landing proportions of a number of variables, year, season and vessel, are analysed for each of the species studied using generalized linear models (GLM). The factor “vessel”, including an ensemble of technical characteristics as well as the abilities of individual skippers, explained most of the model deviance, strongly reinforcing the existence of a fleet component dedicated to catch cephalopods. However, time also explains much of the variation found in the data.Seasonal alternation between landings of octopodidae and cuttlefish was observed within a small group of old trawlers operating mainly off the south coast, following the abundance cycles of these species. For a larger group of more modern trawlers, operating off the western coast, inter-annual shift between octopus and squid was found, together with a well marked seasonal pattern between the catches of cephalopods and horse mackerel.Spatial patterns of activity were identified using vessel monitoring system (VMS) data available for trawlers in Portugal, demonstrating the existence of cephalopod targeting strategies in Portuguese fish trawling activities.     

Nutrient Digestibility of Cereal Grain Products and By‐products in Extruded Diets for Nile Tilapia

Apparent digestibility coefficients (ADCs) provide estimates of nutrient availability in feedstuffs and can be used as a tool for selecting ingredients to compound cost‐effective diets for fish. Extrusion process is one factor that could influence ADC values. Thus, a digestibility trial was undertaken to evaluate ADC of protein, energy, and dry matter, and apparent amino acid availability (AAAA) in five cereal grain products/by‐products (corn, wheat middlings, broken rice, rice bran, and sorghum) in compounded diets for Nile tilapia. Chromic oxide was used as an external inert marker. The digestibility values of energy and dry matter in ingredients, in decreasing order, were highest for broken rice (95.34 and 96.45%), sorghum (82.37 and 87.29%), corn (67.34 and 82.21%), rice bran (57.58 and 55.59%), and wheat middlings (48.94 and 45.88%). Protein digestibility value was higher for corn (72.86%) and the lowest value was observed for sorghum (56.77%), while broken rice, wheat middlings, and rice bran presented values ranging from 63.01 to 66.88%. AAAA values were higher for corn (70.05%) and the lowest methionine and cystine availability values were recorded for wheat middlings and broken rice, respectively. Broken rice appears as one of the most indicated ingredient for using in Nile tilapia diets because of its highest values of nutrient digestibility when compared to the other energetic sources. The use of this information should aid more precise and economic diet formulation for Nile tilapia.     

Growth,absorption and assimilation efficiency by mature cuttlefish (<Emphasis Type="Italic">Sepia officinalis</Emphasis>) fed with alternative and artificial diets

The effects of feeding three natural frozen diets, grass shrimp (Palaemonetes sp.), crayfish (Procambarus clarkii) and fish (Sardina pilchardus) and two semi-humid artificial diets (based on fish powder) to mature cuttlefish, Sepia officinalis, were analysed. Growth and feeding rates (GR and FR, % BW day⁻¹), food conversions (FC, %), and total protein and lipid composition of the diets were determined. Digestive gland to body weight ratio and absorption efficiency were calculated for each diet. Cuttlefish fed shrimp and crayfish grew larger (1.5 and 1.1% BW day⁻¹, respectively) compared to the other diets. Shrimp promoted the highest FC, followed by crayfish, and sardine. The highest FR was obtained for cuttlefish fed crayfish (8.4% BW day⁻¹). Although both artificial diets were accepted, none produced growth. A positive correlation (r = 0.96) between cuttlefish ingestion rate and digestive gland weight was obtained. Some cannibalism occurred among cuttlefish fed the artificial diets during the last week of the experiment. According to the results obtained, P. clarkii could be used as an alternative prey to shrimp for rearing adult mature (>50 g) S. officinalis.     

Effects of binder type and binder addition on the growth of juvenile Palaemonetes varians and Palaemon elegans (Crustacea: Palaemonidae)

This investigation compared the effects of using two binders of no nutritional value, lignosol and agar, and the binding method, microbinding and microcoating, on the growth of juvenile Atlantic ditch shrimp, Palaemonetes varians, and rockpool prawn, Palaemon elegans. Shrimp were fed one basal diet which varied solely in binder type and method of inclusion (Diet A, with lignosol added by microbinding, Diet B, with agar added by microbinding, and Diet C with lignosol added by microcoating) for a period of 45 days. At the end of the experiment significant differences in the final wet weight were found between shrimps fed Diet A and Diet C and between shrimps fed Diet B and Diet C (P < 0.001), but no significant differences were found between Diet A and Diet B (P > 0.05). These results were verified for both species. Significant differences were found between the linear regression slopes of the three tested diets for P. varians (F _3,411 = 3.41; P < 0.04), and for P. elegans (F _3,431 = 10.51; P < 0.0003). Palaemon elegans grew faster than P. varians and at the end of the experiment significant differences were found between the final wet weight of the two species (F _3,842 = 48.17, P < 0.0001). The growth parameters analysed, weight gain (WG), thermal-unit growth coefficient (TGC), and food conversion rate (FCR) were always higher for P. elegans. Results indicate that use of either lignosol or agar, added to the diet by microbinding, is advisable.     

Soybean molasses as an organic carbon source in the farming of Litopenaeus vannamei (Boone, 1931) in a biofloc system

Soybean molasses was evaluated as a partial replacement for sugarcane molasses as a carbon source for biofloc development in the superintensive culture of Pacific white shrimp (Litopenaeus vannamei). A 50‐day study was conducted with juvenile (3.2 g) shrimp stocked in 16 800 L tanks at a stocking density of 250 shrimp m^?3. Control of total ammonia concentration was performed by the addition of combined mixtures of soybean and sugarcane molasses to the culture water. Three different molasses treatments were evaluated using different soybean‐to‐sugarcane molasses ratios: 15–85%, 38–62% and 60–40% respectively. The control group was treated only with sugarcane molasses. Water quality, chlorophyll a concentration, heterotrophic bacterial load, Vibrio spp. concentration and zootechnical indexes were all evaluated. Total ammonia concentration was controlled by heterotrophic and chemotrophic pathways. Biofloc formation, as quantified by measuring the total suspended solids, was not altered. The Vibrio spp. concentration showed a significant reduction in treatments with soybean‐to‐sugarcane molasses ratios of 38–62% and 60–40%. All combined mixtures of soybean and sugarcane molasses could maintain water quality and productivity in the superintensive culture of L. vannamei using the biofloc system. Thus, the potential use of a residue from agroindustry as a carbon source in a biofloc culture is demonstrated.     

Near-Infrared Spectroscopy Coupled with Chemometrics Tools: A Rapid and Non-Destructive Alternative on Soil Evaluation

Near-infrared (NIR) spectroscopy is a rapid, non-destructive and accurate technique for analyzing a wide variety of samples, thus, the growing interest of using this technique in soil science. The objective of this study was to evaluate the potential of NIR spectroscopy to predict organic carbon (OC), total nitrogen (TN), available phosphorus (P) and available potassium (K) in the soil. NIR spectra from 20 cm³ of soil samples were acquired on the range of 750 to 2500 nm in diffuse reflectance mode, resolution of 16 cm^?1 and 64 scans. Eight models of calibration/validation were constructed. Calibration and validation models showed that the predictive potential of NIR varied with the specific soil property (OC, TN, P and K) under evaluation and according to the methodology employed in the model construction (cross-validation or test set). Good prediction models were obtained for OC and TN content based on the statistical parameters. Test set methodology was able to predict soil OC, TN, P, and K better than cross-validation methodology.     

Effect of the conservation procedure on the contents of phenolic compounds and organic acids in chanterelle (Cantharellus cibarius) mushroom

To check the influence of the conservation procedure in the chemical composition of chanterelle mushroom, phenolic compounds and organic acids of samples preserved under four different conditions (drying, freezing, conservation in olive oil and in vinegar) were determined. Phenolics and organic acids were analyzed by HPLC-DAD and HPLC-UV, respectively. The results showed that chanterelle is characterized by the presence of six phenolic compounds (3-, 4-, and 5-O-caffeoylquinic acid, caffeic acid, p-coumaric acid, and rutin) and five organic acids (citric, ascorbic, malic, shikimic, and fumaric acids). Samples preserved in olive oil also exhibited hydroxytyrosol, tyrosol, luteolin, and apigenin, whereas conservation in vinegar led to the detection of hydroxytyrosol, tyrosol, and tartaric acid in the analyzed samples. The conservation procedures to which chanterelle samples were subjected seem to affect the qualitative and quantitative phenolics and organic acids profiles.