Main Components Of Diet Research Articles

A comparison of commercially available feeds for rabbits, guinea pigs, chinchillas and degus with evidence of their diet and feeding behaviour in natural habitats.

A large variety of pet feeds is commercially available for pet herbivores; these feeds may differ in nutrient composition from the natural diet, and may trigger different feeding behaviours than observed in natural habitats. Here, we surveyed literature on the natural diet and activity budget of rabbits (Oryctolagus cuniculus), guinea pigs (Cavia porcellus), chinchilla (Chinchilla lanigera) and degus (Octodon degus), as well as 260 compound feeds commercially available for these species between 1982 and 2020. The species are classified as herbivores, with available data on natural diets suggesting a crude fibre (CF) level of approximately 250 g/kg dry matter (DM), natural feeding activity at a magnitude of 4-7 h per day, with distinctively shorter feeding when fed on compound pet feeds. Only for a minority of feeds did the first 5 listed ingredients not include a starchy ingredient, or only ingredients not considered suitable for human consumption. The percentage of feeds whose CF level was less than 150 g/kg DM was 22 % for production rabbits, 18 % for pet rabbits, 26 % for guinea pigs, 18 % for chinchillas and 14 % for degus; in other words, a majority of currently marketed products have CF levels in accord with published recommendations, even if that means a discrepancy to natural diets. Screening the producers' feeding instructions suggests they should generally not be followed uncritically. No temporal trends in the CF levels of these diets was evident. There is no consensus whether only products resembling natural diet items should be included in pet feeds, or whether vegetable byproducts not edible by humans should also be included. The observed practice of pet feed composition largely did not follow either concept, questioning the general rationale of pet feed composition. Whole forage like hay is recommended as the main diet component for these species, and 76 % of pet feed products noted that hay should be fed in the feeding instructions.

Assessment of Heavy Metals in Fruits and Vegetables Collected from Bareilly Local Market, Uttar Pradesh State, India

Abstract: Heavy metals are among the contaminating agents of our food supply, and the main source of metals or the media through which living beings get exposed to various toxic metals is food and water. The concentration of heavy metals in plants is essential for good health and growth of human and animals but should be within permissible limits. Various natural and anthropogenic factors are responsible for excess metal concentration in crops. Dietary heavy metals such as cadmium, lead, arsenic, mercury can be harmful to biota as their excessive accumulation in human body can lead to systematic health problems. Fruits and vegetables are main component in diet after cereals. Hence the present study aimed to determine Aluminium (Al), Arsenic (As), Cadmium (Cd), Lead (Pb) and Mercury (Hg) content in mostly consumed vegetables (onion, potato, taro root, spinach, taro root leaves, beans, jackfruit and pumpkin) and fruits (blackberry, mango and pears) during summers in Bareilly City, Uttar Pradesh. These food samples were collected from local vendors and shops from four different market sites of the city. The samples were analysed using atomic absorption spectrophotometer and the obtained results were compared with safe limits set by different national and international agencies. Based on the data we conclude that concentrations (mg/kg dry weight) of As, Pb and Hg for all samples and Al and Cd for most of the food stuffs were found exceeding the allowable limits causing potential health risk to consumers of present study area. Elevated levels of these metals in food stuffs might be due to various factors such as usage of industrial and disposal waste water for irrigation, municipal and urban runoff, fertilizers, pesticides, that contaminates the soil and hence crops absorb those metals. Some cultivation areas get exposed to atmospheric pollution found near highways, in form of metal containing aerosols. Other factors can be exposure to pollution during transportation and marketing. The prolonged consumption of unsafe concentration of metals is an alarming public health concerns, considering that metals can accumulate in organism and show negative effects by causing various disruptions of numerous biochemical processes and therefore leading to acute and chronic health outcomes. Such foodstuffs should be avoided in the diet and a regular monitoring is required to avoid the health risk among humans. Keywords: heavy metal, contamination, concentration, food sample, human, toxicity

Feeding habits of Paralabrax nebulifer (Serranidae) during reproductive and non-reproductive seasons in an adjacent area to Magdalena Bay, Baja California Sur, Mexico

The barred sand bass Paralabrax nebulifer is a commercially important fish off the west coast of Baja California Sur. To assess the diet of this species and variations as a function of sex and reproductive condition, 60 specimens were captured using traps during seven seasonal sampling trips from August 2016 to August 2018 in an adjacent area to Magdalena Bay, Baja California Sur, Mexico. The stomach contents of 50 specimens were obtained (23 males and 27 females). Sex was diagnosed by direct observation of the gonads. Based on the gonadosomatic index, hepatosomatic index, and histological analyses, the reproductive season of the barred sand bass was corroborated for August 2016, April, August, and September 2017, and August 2018, and the non-reproductive season was corroborated for November 2016 and March 2018. The Index of Relative Importance (IRI) was used to classify the main diet components, which comprised three fish species, seven crustacean species, and one mollusk species. According to the IRI, the South American pilchard Sardinops sagax and the red pelagic crab Pleuroncodes planipes were the prey that contributed the most (55%) to the barred sand bass diet. The ANOSIM showed that there were significant differences in the amount and type of prey consumed by sex; the SIMPER analysis revealed that the species contributing the most to differences between the sexes were S. sagax (16.58%), Euphylax dovii (15.95%), Stenocionops ovata (12%), and P. planipes (11.82%) for females. There were significant differences in the amount and type of prey consumed between types of reproductive season; the species contributing the most to differences between seasons were Anchoa spp. (27.76%), and P. planipes for non-reproductive season (22.67%), and S. sagax (11.08%) for reproductive season. The feeding strategy of the barred sand bass was that of a specialist carnivorous predator that fed mainly on the fish Sardinops sagax during the reproductive season, which supply the dietary nutritional requirements of the lipids HUFA (arachidonic acid, 20:4n-6; eicosapentaenoic acid, 20:5n-3; docosahexaenoic acid, 22:6n-3), nutrients required to achieve reproductive success.

Complementary use of stable isotopes and fatty acids for quantitative diet estimation of sympatric predators, the Antarctic pack-ice seals

The quantitative use of stable isotopes (SIs) for trophic studies has seen a rapid growth whereas fatty acid (FA) studies remain mostly qualitative. We apply the Bayesian tool MixSIAR to both SI and FA data to estimate the diet of three sympatric predators: the crabeater (Lobodon carcinophaga), Weddell (Leptonychotes weddellii) and leopard seal (Hydrurga leptonyx). We used SI data of their vibrissae and FA data of their outer blubber to produce comparable diet estimates for the same individuals. Both SI and FA models predicted the same main diet components, although the predicted proportions differed. For the crabeater seal, both methods identified krill, Euphausia superba, as the main, and almost exclusive, food item, although the FA model estimated a slightly lower proportion, potentially due to the low lipid content of krill compared to the fish species used in the model. For the Weddell seal the FA model identified the fish Pleuragramma antarcticum as the most important prey, whereas the SI model was not able to distinguish among prey species, identifying a ‘fish-squid’ group as the main diet component. For the leopard seal, both models identified krill as the main contributor; however, the predicted proportions for the secondary sources differed. Although vibrissae and outer blubber may not represent the same timeframe, the use of MixSIAR with FA data provides diet estimates comparable to those obtained with SI data, thus, both approaches were complimentary. The use of both biotracers offers a feasible option to study diets of wild animals in a quantitative manner.

The golden jackal (Canis aureus) and the African swine fever pandemic: Its role is controversial but not negligible (a diet analysis study).

BackgroundIn Europe, the African swine fever (ASF) pandemic mostly affects the environmental domain of health, which is a strongly human‐impacted ecosystem. However, the current control strategies focus solely on the wild boar and tend to disregard other epidemiologically relevant elements of the ecosystem.ObjectivesThis study investigated the potential impact of the golden jackal on the surveillance effort and disease transmission.MethodsFor this reason, the authors analysed the content of 277 stomachs of this canid species within its westernmost inhabitant population, in order to determine the amount of suid remains, disposed.ResultsThe findings confirmed that in a densely populated wild boar habitat, the main diet component of jackals was wild boar all the year round. The jackals disposed of 0.3–0.6 kg/km2/day offals that potentially contained suid remains. On the other hand, the scavenging activity removed the most important target objects on which the passive surveillance of ASF should be based.ConclusionsThis study cannot determine whether canid scavengers positively or negatively influence the control efforts; however, the impact of the jackal should not be disregarded. The results warn the necessity of a multidisciplinary approach to complex epidemiological situations within different ecosystems.

Small-Scale and Long-Term Variability in Population Dynamics of the Cockle Cerastoderma edule in a Southern North Sea Tidal Flat System

The cockle Cerastoderma edule is one of the most common macrofauna species in the Wadden Sea areas of the North Sea. Cockle population dynamics are influenced by various abiotic and biotic factors such as temperature, food availability, and inter- and intraspecific competition. Cockles play an important role in the food web of the Wadden Sea, for instance, large shellfish-eating birds, such as oystercatchers and common eiders, use the cockle C. edule and the blue mussel Mytilus edulis as a main diet component. However, the populations of shellfish-eating bird species have been declining dramatically across the Wadden Sea since the beginning of the 21st century. While there are detailed monitoring programs in blue mussels due to commercial interests, little information is known about the stocks and long-term dynamics of cockles in the German Wadden Sea. To fill this gap, in 2005 a local conservation society (“Der Mellumrat e.V.”) initiated a study to sample cockles at one transect per year south of the island of Mellum, which was extended by 5 more transects in 2011. In addition to the spatial analysis, we analyzed the long-term variability in cockle population dynamics. Min/max autocorrelation factor analysis (MAFA) revealed a decline in cockle abundance, while no clear length trends were found. Canonical and spearman correlation analyses exposed significant correlations between cockle abundance and length and chlorophyll a, mussel bank area as well as oystercatcher and common eider populations. This study clearly shows that there is an urgent need for comprehensive time series of cockle data to analyze and explain ecological long-term changes in cockle population dynamics in relation to environmental changes and to point out how parts of the Wadden Sea food web, such as shellfish-eating birds are affected by these changes.

Assessment of diet composition of free-ranging addax antelopes (Addaxnasomaculatus) by the combination of microhistological procedures andn-alkanes and long-chain alcohols as fecal markers

Understanding herbivore foraging behaviour is crucial for adequate wildlife management decisions. This study assessed the diet composition of free-ranging addax antelope (Addax nasomaculatus (de Blainville, 1816)). Samples collected during the spring season were analyzed using microhistological procedures along with n-alkanes and long-chain alcohols as fecal markers. Twelve animals were monitored and fresh fecal samples were collected daily during a 7-day period. Diet composition estimates obtained by both methods were similar and indicate that Stipagrostis pungens (Desf.) De Winter was the main diet component followed by Fagonia glutinosa Delile, Helianthemum kahiricum Delile, and Hammada schmittiana (Pomel.) Botsch. Data showed that addax have mixed diets composed of perennial woody and herbaceous plant species depending on their availability. The four species most selected by the animals were also the most abundant species in terms of plant cover. In contrast, species that accounted for less than 5% of the plant cover were not present in the fecal samples. Results of this study represent a single grazing season, and for that reason, further studies are required to fully understand how the grazing behaviour of addax varies with seasonal changes in vegetation cover.

SEASONAL CHANGES OF THE MORPHO-BIOLOGICAL CHARACTERISTICS OF BLACK ROCKCOD NOTOTHENIA CORIICEPS (NOTOTHENIIDAE) IN THE ARGENTINE ISLANDS ARCHIPELAGO REGION

Black rockcod Notothenia coriiceps (Nototheniidae) is one of the common fish species of the Argentine Islands Archipelago region, and it is very common in the Southern Ocean waters. So, objective of the original research was to study the seasonal changes of biological characteristics of N. coriiceps individuals. The material was collected during the XII Ukrainian Antarctic Expedition in 2007-2008 using classical methods, specifically by the bottom gear in the ice-free water places from the boat and from the shore, and in winter also from the ice. Pieces of fresh meat and fish were used as bait for gear. The catches were carried out at the depths from 10 to 50 m (mainly at depths of 20-30 m). Result The majority of black rockcod has a standard length of 26,0-30,0 cm (45,3%) and the age of 4-5 full years (84,5%). During the year, the majority of individuals has II stage of development of the gonads (82,9%), however the number of individuals whitch have III and over stage of development has gradually increased from October to January. It was detected that the main diet components of N. coriiceps in the Argentine Islands Archipelago region were fish and crustaceans rarely – mollusks. Two size groups (>25 cm and <25 cm) of black rockod had the same feeding components ratios. In the majority of individuals (67,7%), the gastrointestinal tract was filled poorly (0-1 point). Fat content during the year was predominantly 2-3 points (94,3%). The value of cardiosomatic index during the year has gradually increased from 0,181±0,008 in April to 0,283±0,005 in September and has again decreased to 0,182±0,003 in December. The value of hepatosomatic index has decreased from 2,11±0,10 in April to 1,58±0,06 in November. In December and January the index has increased to 2,66±0,57. The value of fatness by Fulton has decreased from 1,89±0,06 in April to 1,60±0,03 in September, in January it has increased to 1,86±0,52. Conclusions: the character of feeding and development stage of N. coriiceps in the region of the material collection has matched with data from the other researches of the other Antarctic Peninsula regions. In the majority of representatives (66,7%), the gastrointestinal tract was poorly filled (0-1 point), and fat content during the year was predominantly 2-3 points (94,3%). The biological features of N. coriiceps were characterized by the seasonal dynamics, that was associated with the feeding in summer and small amount of food in winter.

Chicken Viscera Meal as a Main Component in Diet for African Catfish Clarias gariepinus (Burchell 1822) Reared in Earthen Ponds

The effects of replacement of fishmeal (FM) with chicken viscera meal (CVM) on growth, body composition and production of Clarias gariepinus fingerlings (initial body weight 11.3 ± 0.1 g) was studied for 90 days. Three isonitrogenous (43 % crude protein) and isoenergetic (20 KJ/g) diets were formulated to containing 0% (diet CMV0), 30% (diet CVM30) and 50% (diet CVM50) of chicken viscera meal (CVM), as FM replace. Diet CVM0, without CVM, acted as a control whereas the commercial diet coppens developed for C. gariepinus was used to validate the experimental design. Feed intake value (247.17-262.0 g) was similar in fish fed Coppens, CMV0 and CMV50, and significantly higher in fish fed CMV30 (p 0.05). Food conversion ratio (1.11-1.19) was significantly higher in fish fed CMV50 diets (p 0.05). Lipid content in fish fed with CVM-based-diets was significantly higher, whereas ash significantly decreased (p<0.05). The study demonstrated that up to 30 % of CVM could be incorporated in the diets of C. gariepinus without negative effects on growth and whole body composition. Therefore, we recommended that CVM could be used to partially replace the expensive and imported FM.

Grizzly bear diet shifting on reclaimed mines

Industrial developments and reclamation change habitat, possibly altering large carnivore food base. We monitored the diet of a low-density population of grizzly bears occupying a landscape with open-pit coal mines in Canada. During 2009–2010 we instrumented 10 bears with GPS radiocollars and compared their feeding on reclaimed coal mines and neighboring Rocky Mountains and their foothills. In addition, we compared our data with historical bear diet for the same population collected in 2001–2003, before extensive mine reclamation occurred. Diet on mines (n=331 scats) was dominated by non-native forbs and graminoids, while diets in the Foothills and Mountains consisted primarily of ungulates and Hedysarum spp. roots respectively, showing diet shifting with availability. Field visitation of feeding sites (n=234 GPS relocation clusters) also showed that ungulates were the main diet component in the Foothills, whereas on reclaimed mines bears were least carnivorous. These differences illustrate a shift to feeding on non-native forbs while comparisons with historical diet reveal emergence of elk as an important bear food. Food resources on reclaimed mines attract bears from wilderness areas and bears may be more adaptable to landscape change than previously thought. The grizzly bear’s ready use of mines cautions the universal view of this species as umbrella indicative of biodiversity.

Composición de la dieta del oso andino Tremarctos ornatus (Carnivora: Ursidae) en nueve áreas naturales protegidas del Perú

The diet of the andean bear Tremarctos ornatus was assessed in dry equatorial, tropical rainy, premontane, montane, and upper montane forests, and puna, whithin nine natural protected areas in Peru (Laquipampa, Chaparri, Cutervo, Yanachaga, Yanesha, Megantoni, Amarakaeri, Manu and Machu Picchu) between 2001 and 2008. Six hundred forty six records were obtained related to the bear’s diet: 522 (80.8%) food waste, 62 (9.6%) feces, 55 (8.5%) climbed trees with sign supplies, and 7 (1.1%) scrabbled roots and trunks. Two animal (1.7%) and 114 plant species (98.3%) included in 36 families, were identified. Fruits (35.2%), leaf bases (31.9%), stems (12.3%), and piths (10.2%) were the eaten plant parts. Bromeliaceae (58.5%), Arecaceae (10.3%), Cyclanthaceae (5.9%) and Poaceae (4.1%) were the botanical families most frequently used. The piths of palms (Arecaceae) were the main diet components in the tropical rainy and premontane forests, the fruits were during the rainy season in the dry equatorial one, while the resource availability produced diverse diets in the montane forest. Key words: andean bear, diet, feeding, Peru, protected natural areas.

Natural history, physiology and energetic strategies of Asellia tridens (Chiroptera)

We used radio-telemetry, observations and physiological measurements to study the basic biology and energetic strategies of Asellia tridens in northern Israel from 2009 to 2010. Between late May and early November, the bats occupied abandoned man-made structures in this area. Parturition occurred between late June and mid-July, and juveniles were independent by late August. A. tridens foraged near the roost in a vegetation-rich, cluttered background environment, catching insects flying close to vegetation. Its diet was diverse, with Coleoptera, Heteroptera, Diptera and Lepidoptera being the main diet components. During summer, males and females differed in their foraging patterns and energetic strategies: Lactating females departed for more frequent foraging bouts than males, and maintained euthermy throughout the day, while males became torpid on a daily basis.

Diet composition in the Tengmalm’s Owl Aegolius funereus: a comparison of camera surveillance and pellet analysis

During a two-year study in Central Europe, we used a combination of pellet analysis and camera recordings to assess the diet composition of Tengmalm’s owl during the breeding season, with regards to availability of the main prey components in the field. The diet of the owls consisted mainly of voles (Arvicolidae), mice (Muridae) and shrews (Soricidae), and their proportion in the diet reflected their local abundances in the field. Pellet analysis allowed us to determine 40.2 ± 6.9 % (2004) and 46.4 ± 14.7 % (2006) of all delivered prey items recorded by cameras, while it was 77.1 ± 17.1 % (2004) and 80.2 ± 12.5 % (2006) for camera monitoring respectively. Pellet analysis underestimated the proportions of all main diet components, but only voles and birds showed statistically significant differences. We suppose that the underestimation of voles is a consequence of their decapitation before delivery to the nest. We regularly recorded decapitated voles and mice in the nest boxes of Tengmalm’s owl, while whole shrews were found more often. Our study highlights that a combination of both methods allows for a more accurate assessment of diet composition in nocturnal raptor species.

Diet shift of double-crested cormorants in eastern Lake Ontario associated with the expansion of the invasive round goby

The proliferation of the invasive round goby ( Apollonia melanostoma) in the Great Lakes has caused shifts in the trophic ecology in some areas. We examined the diet of double-crested cormorants ( Phalacrocorax auritas) prior to, and immediately after, round goby population expansion at two colonies, Pigeon and Snake Islands, in eastern Lake Ontario from 1999 to 2007. Cormorant diet was determined from the examination of 10,167 pellets collected over the nine-year period. By the second year round gobies were found in the diet (2002 at Snake Island and 2003 at Pigeon Island) they were the main species consumed by cormorants at each colony. The dominance of round goby in cormorant diets had a significant effect on both daily fish consumption and seasonal trends in fish consumption compared to the pre-goby years. Seasonal differences that were observed during the pre-goby years were lost once gobies became the main diet component of cormorants. The rapid switch to a benthic prey such as round goby, from a largely limnetic fish diet demonstrates the adaptive foraging ability of cormorants. Round goby may act as a buffer for yellow perch and smallmouth bass, two sport fish impacted by cormorant predation in eastern Lake Ontario.

Tidal movements of East Pacific green turtle Chelonia mydas at a foraging area in Baja California Sur, México

We tracked East Pacific green turtles Chelonia mydas using GPS-VHF telemetry in Estero Banderitas, a tidally-influenced foraging area in Bahia Magdalena, Baja California Sur, Mexico. Tidal currents were measured with a bottom-mounted Acoustic Doppler Profiler (ADP) and the data used to predict tidal current speed and direction at the location and time during which turtles were tracked. Twenty-nine turtles were tracked in the summers of 2000 to 2003. Vagility (mean ± SD; 18.6 ± 11.4 km d -1 ) and speed (0.83 ± 0.47 km h -1 ) of turtles was the greatest so far reported for green turtles at foraging areas. Turtles displayed highly linear movements, and move- ment patterns were circatidal. Vector correlation was used to compare turtle speed and direction with tidal speed and direction. Correlation coefficients were significant for 11 out of 13 tracks, indicating significant linear interdependence between turtles and tides. Speed and direction contributed equally to the correlation. Results indicated a new paradigm for green turtles in feeding areas, where turtles are transported on continual tides that allow them to exploit a patchy and seasonal distribution of algae, their main diet component. This tidal transport is markedly different than Selective Tidal Stream Transport, in which animals use either the ebb or flood tide for transport. Tidal currents may be an accurate indicator of turtle movement in tidal areas, and this transport system has implications for foraging ecology, energetics, and growth.

Diet composition, herbage intake and digestibility in Inner Mongolian Cashmere goats grazing on native Leymus chinensis plant communities

The botanical composition, intake and digestibility of the diet selected by Inner Mongolian Cashmere goats grazing on a native Leymus chinensis plant community were measured in two grazing periods (June and August) using the n-alkane markers. In each grazing period, 48 Inner Mongolian Cashmere goats (24 wethers and 24 does with an average live weight of 22.1 ± 1.2 kg and 19.6 ± 0.8 kg, respectively) were divided in two groups (G1: grazing group; G2: cage-fed group) of 24 animals each. Based on the observation of G1 grazing behaviour, G2 goats were fed on herbage obtained by a simulative method and were housed in metabolism cages to determine the alkane faecal recoveries. Diet composition was estimated by comparing the odd-chain n-alkane pattern (C 25–C 35) of the selected plant species with the n-alkane faecal concentrations, corrected for their incomplete faecal recovery. The alkane pair C 32:C 33 and C 36 alkane were used to estimate intake and diet digestibility, respectively. The results showed that the increase of herbage availability from June to August, resulted in higher ( P < 0.05) DM, CP, ME, ADF and NDF intake of both wethers and does, with no evident changes in ADF and NDF intake in does., The intake of nutrients differed significantly between wethers and does in both experimental periods, except for NDF in EP1 and ME in EP2. Differences between grazing seasons and goats' sex in nutrients digestibility were not observed. Diet composition indicated seasonal differences, being Sonchus brachyotus, Artemisia frigida and Phragmites communis the main components of the diet in June. However, Suaeda corniculata, Chloris virgata, Xanthium sibiricum and Echinochloa crusgalli became the main diet components in August. Moreover, the sex affected significantly the diet choices in both grazing periods.

Effects of stocking density on growth, yield and profitability of farming Nile tilapia, Oreochromis niloticus L., fed Azolla diet, in earthen ponds

Two consecutive experiments were conducted to study the effects of stocking density on growth, food utilization, production and farming profitability of Nile tilapia (Oreochromis niloticus) fingerlings (initial mean weight: 16.2 ± 0.2 g) fed Azolla, as a main component in diet. In experiment 1, fish were hand-fed twice daily with three isonitrogenous (28.5% crude protein) and isocaloric (14.5 kJ g−1) diets A30, A35 and A40 containing 30%, 35% and 40%Azolla, respectively, for 90 days. Diets were formulated by mixing Azolla with locally available by-products. No significant differences were found in growth parameters and production (P>0.05). Total investment cost was significantly higher with A30 (P 0.05). In experiment 2, three stocking densities, 1, 3 and 5 m−2, were assigned to three treatments T1, T2 and T3 respectively. Fish were hand-fed twice daily with diet A40. The final mean weight (89.53–115.12 g), the mean weight gain (0.81–1.10 g day−1), the specific growth rate (1.90–2.20% day−1) and the apparent food conversion ratio (1.29–1.58) were affected by stocking density, with significant difference (P 0.05). Yield and annual production increased with increasing stocking density, ranging from 7.10 ± 0.90 to 25.01 ± 1.84 kg are−1 and 28.79 ± 3.66 to 101.42 ± 7.48 kg are−1 year−1, respectively, with significant differences between all densities (P<0.05). Higher stocking density resulted in higher gross return and lower cost of fish production, with significant variations (P<0.05). The net return increased with increasing stocking density (P<0.05). However, both densities of 3 and 5 m−2 produced the same profitability values. On the basis of growth values and economic return, it was concluded that Nile tilapia could be raised at a density of 3 fish m−2 with A40 to improve production and generate profit for nutritional security and poverty alleviation in rural areas.

Prey selection by North Sea herring (Clupea harengus), with special reference to fish eggs

Abstract Segers, F. H. I. D, Dickey-Collas, M., and Rijnsdorp, A. D. 2007. Prey selection by North Sea herring (Clupea harengus), with special reference to fish eggs. ICES Journal of Marine Science, 64: 60–68. he herring stock in the North Sea in recent years has recovered to a relatively high biomass, and here we investigate prey selection of individual North Sea herring when population numbers are high. The diet composition, and specifically pelagic fish eggs, was investigated in February 2004. Samples of herring from the International Bottom Trawl Survey were used for stomach analysis, and ichthyoplankton samples from the southern North Sea were used to investigate selection. Crustaceans were the main diet component. The average diameter of the fish eggs recovered from the stomachs was significantly larger than that of the eggs collected in the field. In addition, the frequency at which the latest developmental stages occurred in the herring stomachs was significantly different from the frequency at which these stages were found in the field. This shows selective foraging. There was a relationship between the amount of food and the number of eggs in a herring stomach: the fullest stomachs tended to contain fewer fish eggs. This suggests that herring forage on eggs when other prey are not available. Hence, it is likely that the dynamics of multiple trophic levels influence the ecological impact of a large herring stock on the North Sea ecosystem.

Diets of Plains Vizcacha, Greater Rhea and Cattle in Argentina

Food habits of plains vizcacha (Lagostomus maximus), greater rhea (Rhea americana) and cattle (Bos taurus) in the Parana? River Delta, Argentina, were studied over 2 years using microhistological analysis of faeces. This was the first study of feeding habits of these herbivores grazing in common in a wetland of Argentina. Poaceae was the main diet component throughout the year for all 3 herbivores, with the exception of spring and summer, when greater rhea consumed a higher proportion of Prosopis nigra (Griseb.) pods. Botanical composition of plains vizcacha and cattle diets was generally similar for the same season but different from that of greater rhea. Panicum milioides Nees., Dichondra microcalyx (Hallier) Fabris. and P. nigra were the most consumed species for vizcacha, while P. nigra, Plantago myosuros Lam., Solanum sp. L., Spilanthes stolonifera (H. et A.) Baker and D. microcalyx dominated the greater rhea diet. The species most consumed by cattle were Luziola peruviana Gmel. and P. milioides. Similarities between the diets of plains vizcacha and cattle seem to support the ranchers' view that vizcachas compete with domestic herbivores for forage. However, high overlap in food habits would result in competition only if forage is scarce. Greater rhea and cattle have different foraging patterns and hunting of greater rhea is not justified solely on the basis of forage competition with cattle. DOI:10.2458/azu_jrm_v56i1_pereira

Diets of plains vizcacha, greater rhea and cattle in Argentina

Food habits of plains vizcacha (Lagostomus maximus), greater rhea (Rhea americana) and cattle (Bos taurus) in the Parana? River Delta, Argentina, were studied over 2 years using microhistological analysis of faeces. This was the first study of feeding habits of these herbivores grazing in common in a wetland of Argentina. Poaceae was the main diet component throughout the year for all 3 herbivores, with the exception of spring and summer, when greater rhea consumed a higher proportion of Prosopis nigra (Griseb.) pods. Botanical composition of plains vizcacha and cattle diets was generally similar for the same season but different from that of greater rhea. Panicum milioides Nees., Dichondra microcalyx (Hallier) Fabris. and P. nigra were the most consumed species for vizcacha, while P. nigra, Plantago myosuros Lam., Solanum sp. L., Spilanthes stolonifera (H. et A.) Baker and D. microcalyx dominated the greater rhea diet. The species most consumed by cattle were Luziola peruviana Gmel. and P. milioides. Similarities between the diets of plains vizcacha and cattle seem to support the ranchers' view that vizcachas compete with domestic herbivores for forage. However, high overlap in food habits would result in competition only if forage is scarce. Greater rhea and cattle have different foraging patterns and hunting of greater rhea is not justified solely on the basis of forage competition with cattle.