Geo-referencing remote images for precision agriculture using artificial terrestrial targets

The aim of this paper is to assess co-registration errors in remote imagery through the AUGEO system, which consists of geo-referenced coloured tarps acting as terrestrial targets (TT), captured in the imagery and semi-automatically recognised by AUGEO2.0^® software. This works as an add-on of ENVI^® for image co-registration. To validate AUGEO, TT were placed in the ground, and remote images from satellite Quick Bird (QB), airplanes and unmanned aerial vehicles (UAV) were taken at several locations in Andalusia (southern Spain) in 2008 and 2009. Any geo-referencing system tested showed some error in comparison with the Differential Global Positioning System (DGPS)-geo-referenced verification targets. Generally, the AUGEO system provided higher geo-referencing accuracy than the other systems tried. The root mean square errors (RMSE) from the panchromatic and multi-spectral QB images were around 8 and 9 m, respectively and, once co-registered by AUGEO, they were about 1.5 and 2.5 m, for the same images. Overlapping the QB-AUGEO-geo-referenced image and the National Geographic Information System (NGIS) produced a RMSE of 6.5 m, which is hardly acceptable for precision agriculture. The AUGEO system efficiently geo-referenced farm airborne images with a mean accuracy of about 0.5–1.5 m, and the UAV images showed a mean accuracy of 1.0–4.0 m. The geo-referencing accuracy of an image refers to its consistency despite changes in its spatial resolution. A higher number of TT used in the geo-referencing process leads to a lower obtained RMSE. For example, for an image of 80 ha, about 10 and 17 TT were needed to get a RMSE less than about 2 and 1 m. Similarly, with the same number of TT, accuracy was higher for smaller plots as compared to larger plots. Precision agriculture requires high spatial resolution images (i.e., <1.5 m pixel^?1), accurately geo-referenced (errors <1–2 m). With the current DGPS technology, satellite and airplane images hardly meet this geo-referencing requirement; consequently, additional co-registration effort is needed. This can be achieved using geo-referenced TT and AUGEO, mainly in areas where no notable hard points are available.     

Soil apparent electrical conductivity and geographically weighted regression for mapping soil

To resolve the spatial variation in soil properties intensively is expensive, but such knowledge is essential to manage the soil better and to achieve greater economic and environmental benefits. The objective of this study was to determine whether the soil apparent electrical conductivity (EC_a), alone or combined with other variables, is a useful alternative for providing detailed information on the soil in the Extremadura region of Spain. Apparent soil electrical conductivity was measured and geographically weighted regression was used to characterize the spatial variation in soil properties, which in turn can be used for soil management. This study shows that soil cation exchange capacity, calcium content, clay percentage and pH have a relatively strong spatial correlation with EC_a in the soil of the study area.     

Effective use of glucose rather than starch in formulated semimoist diets of common octopus (Octopus vulgaris)

The aim of the present work was to test the capacity of O. vulgaris to use carbohydrates supplied in three diets: a diet without added carbohydrates (diet C0: 500 g kg^?1 water, 200 g kg^?1 gelatine, 100 g kg^?1 egg yolk powder, 50 g kg^?1 freeze‐dried Sardinella aurita and 150 g kg^?1 freeze‐dried Todarodes sagittatus), and two obtained by substituting 50 g kg^?1 of T. sagittatus by glucose (diet GLU50) or by starch (diet STA50). The most stable and best accepted diet was STA50 (SFR 1.26%BW day^?1), although there were no significant differences in the growth rates obtained with the three diets: 10.1 g day^?1, 9.4 g day^?1 and 11.2 g day^?1 for C0, GLU50 and STA50, respectively (P > 0.05). The feed efficiency indices were better for GLU50, of particular note being the protein productive value of 72% and a feed conversion ratio lower than 1. Protein and lipid digestibility were similar in all three diets (96–98% for proteins and 85–94% for lipids), whereas carbohydrate digestibility was higher in GLU50 (98%) than in C0 (84%) and STA50 (0.33%). The content of carbohydrates increased in muscle and the digestive gland as a consequence of the increased carbohydrates intake.     

Evaluation of poultry by‐product meal as partial replacement of fish meal in practical diets for juvenile tench (Tinca tinca L.)

The aim of this study was to evaluate different replacement levels of fish meal (FM) by poultry by‐product meal (PBM) on survival, growth performance and body composition of juvenile tench (Tinca tinca). A 90‐day experiment was conducted with 5 month‐old juveniles (31.95 mm total length, 0.396 g weight). Eight practical diets (50% crude protein) differing in the level of replacement of FM protein by PMB protein were tested: 0% (control), 25%, 31%, 37%, 43%, 49%, 55% and 61% corresponding to 0, 184.8, 229.2, 273.5, 317.8, 362.1, 406.5 or 450.8 g PBM kg^?1 diet respectively. Significant differences were not found (P > 0.05) between 25% replacement of FM protein by PBM protein (184.8 g kg^?1 PBM in diet) and control diet. At higher replacement levels, fish had significantly lower growth, higher feed conversion ratio and lower protein productive value (P < 0.05). Fish with externally visible deformities ranged from 1.1% to 3.3%. The relation among amino acid profiles of the diets, body composition, growth performance of juveniles and amino acid requirements of other fish species is discussed. Up to 184.8 g PBM kg^?1 diet can be included in diets for juvenile tench without impairing growth performance.     

Effects of including shrimp protein hydrolysate in practical diets on the growth and survival of redclaw crayfish hatchlings Cherax quadricarinatus (Von Martens, 1868)

An experiment was carried out to analyse the effects of substituting fish‐meal (FM) with soya bean meal and shrimp protein hydrolysate (SPH) on the percent survival, growth rate, feed efficiency and molt frequency of redclaw crayfish hatchlings, Cherax quadricarinatus. The experiment was performed in a closed recirculating‐water system over a 56‐day period. Five diets were tested: a control diet (SPH₀) comprising 100% FM without SPH, and four diets with 2.5%, 5.0%, 10.0% and 15.0% SPH substitution (diets SPH_2.5, SPH₅, SPH₁₀ and SPH₁₅ respectively). Analysis of water quality indicated that it was adequate to maintain a good growth and survival of hatchlings. The results showed that 100% survival was obtained for hatchlings fed with SPH₅, SPH₁₀ and SPH₁₅ diets. Higher mean values of final weight were obtained for the SPH₅ diet. The highest weight gain was observed in SPH_2.5 and SPH₅ diets. Hatchlings showed similar specific growth rates for all diets. The efficiency rate of the SPH₁₅ diet was lower compared to the other diets. Overall, individual feed consumption was higher in hatchlings fed diets of SPH₅ and SPH₁₅. It is recommended that 5.0% of SPH could be included in diets of hatchling redclaw crayfish to improve their growth efficiency.     

Abundance and genetic diversity of the red crab Pleuroncodes planipes along the western coast of the Baja California Peninsula, Mexico

This study reports the distribution, estimated abundance and biomass, and genetic population structure of the red crab Pleuroncodes planipes along the western coast of the Baja California Peninsula, Mexico. Using a hybrid conical net for fish and crustaceans, bottom trawls with stratified depth were performed at transect sites perpendicular to the coast. Red crab was observed to distribute widely in the study area, particularly in upwelling areas such as Bahia Magdalena and its surroundings, and the greatest catches were recorded at depths between 51 and 100 m, and between 201 and 300 m, with values of 2,297 and 3,223 kg/h of trawl, respectively. The population genetic analysis using mitochondrial DNA sequencing revealed no significant population differentiation. The total estimated biomass was 611,525 metric tons, supporting the proposal that the red crab is a viable exploitation resource in the study area.     

MARKET DELINEATION OF THE SPANISH CLAM MARKET

This article analyzes the long-term relationship among prices of the most consumed clams in Spain. The clams considered are: the striped venus (Chamelea gallina) from Spain and Italy, the Japanese carpet shell (Ruditapes philippinarum) and the grooved carpet shell (Ruditapes decussatus). The striped venus and grooved carpet shell are wild-caught whereas the Japanese carpet shell is from aquaculture farms. Unit root tests were used to check for stationarity and cointegration and the Law of One Price (LOP) were analyzed. Also short-run and long-run causality among prices is studied. The empirical results show that the markets for the Italian and Spanish striped venus and the Japanese carpet shell are interrelated and to some extent these clams can be considered to be substitutes. However, only the Japanese carpet shell and the Spanish striped venus are perfect substitutes.     

Marine gammarids (Crustacea: Amphipoda): a new live prey to culture Octopus maya hatchlings

The effects of feeding two alternative live prey Hyalella azteca (freshwater gammarids) and Hyale media (marine gammarids) to Octopus maya hatchlings were compared with feeding adult Artemia sp., traditionally used during the first weeks of the life cycle. Hatchlings were fed ad libitum these three live preys during the first 15 days, and a paste elaborated with fresh squid and shrimp during the next 15 days when hatchling can be fed prepared diets. Weight (g) and specific growth rates (% day^?1) were determined every 15 days. Octopus maya hatchlings fed with marine gammarids grew larger (6.9 ± 0.2% day^?1) compared with hatchlings fed Artemia sp. or freshwater gammarids (4.8 ± 0.2% and 5.0 ± 0.3% day^?1 respectively). Survival was also higher (92.2 ± 6.8%) for hatchlings fed marine gammarids, than for those fed Artemia sp. (74.5 ± 23.8%) or freshwater gammarids (41.2 ± 21.2%). The content of acylglycerides, cholesterol and proteins in O. maya fed marine gammarids suggested a better nutrient assimilation by the hatchlings. Also, polyunsaturated fatty acids levels (EPA and DHA) were more abundant in marine gammarids, possibly contributing to the higher growth rates observed. This is the first study revealing a successful use of marine gammarids as alternative prey for octopus hatchlings culture.     

Influence of dietary administration of a probiotic strain Shewanella putrefaciens on senegalese sole (Solea senegalensis,Kaup 1858) growth,body composition and resistance to Photobacterium damselae subsp piscicida

Probiotics are currently being supplemented to cultured fish due to their benefits for fish performance. Herein, we tested the health protection and nutritional effects of probiotic Shewanella putrefaciens (Pdp11 strain), both fresh and lyophilized cells, on Senegalese sole (Solea senegalensis) juveniles. Pdp11 was incorporated into fish feed at concentration of 10⁹ cells g^?1, and then provided to juvenile sole for 2 months. Growth rates were significantly higher in fish fed the fresh probiotic compared with fish fed the control diet. Growth of fish receiving lyophilized bacteria was not improved when compared with controls. Body compositions (protein, total lipids and fatty acids profile) were similar for each dietary treatment. At the end of the study, fish were challenged by intraperitoneal inoculation with a pathogenic strain of Photobacterium damselae subsp. piscicida. Relative percentages of survival (RPS) ranged between 25% and 43.8% for fish receiving both probiotic supplemented diets. Both fresh and lyophilized Pdp11 cells conferred protection against P. damselae subsp. piscicida. However, only fresh Pdp11 enhanced Senegal sole performance. These findings should be taken into account for industry purposes in which lyophilized Pdp11 might be easier to manage.     

Use of the probiotic Shewanella putrefaciens Pdp11 on the culture of Senegalese sole (Solea senegalensis, Kaup 1858) and gilthead seabream (Sparus aurata L.)

The application of probiotics on aquatic animals is increasing for a better fish welfare status as well as an environment-friendly activity which are actual demands of modern aquaculture industry. A bacterium from skin mucus of healthy gilthead seabream (Sparus aurata L.) has been isolated and identified as Shewanella putrefaciens Pdp11. Different studies have been done to know its application as probiotic in the Senegalese sole and gilthead seabream farming. This article reviews the studies carried out with this probiotic microorganism focusing on the current knowledge of its in vitro and in vivo mechanisms of action. The results suggested that the probiotic S. putrefaciens Pdp11, due to its beneficial effects, could be used in the aquaculture activity of both species.