Feeding Intensity Research Articles

The diet of juvenile Atlantic mackerel (Scomber scombrus) feeding in new northern nursery areas along the Norwegian coast

ABSTRACT The North-east Atlantic mackerel stock size increased substantially from 2006–2014 coinciding with high recruitment. This resulted in a pronounced northerly geographic expansion of mackerel, followed by an influx of juvenile mackerel into Norwegian waters. The objective of this work was to study the diet and feeding intensity of juvenile mackerel at the new nursing grounds along the Norwegian coast during the summer. Juvenile mackerel were feeding as far north as 70°N. Stomach content was analysed for the first time from co-occurring juvenile and adult mackerel at the same locations. Almost 80% of all juvenile mackerel had prey in their stomachs, and juveniles had similar stomach fullness as adult mackerel in the same areas. The juveniles preyed on a wide variety of prey species and seemed to utilize both passive filter feeding and active particulate feeding. The most abundant prey group was Appendicularia, accounting for 31% of the stomach content by weight. Juveniles fed on similar prey species as adults, but their diet niche differed somewhat as adult mackerel fed more on krill. Juvenile mackerel can thus successfully survive and feed on various prey in high latitudes and can potentially be a feeding competitor to other planktivorous fish species in the area.

Particle size distribution in commercial pig compound feeds in Switzerland: survey and methodological considerations.

The grinding intensity of pig feed is considered one potential predisposing factor for gastric ulcers, and a variety of particle size recommendations have been published for pig feeds. We subjected 51 different commercial compound feeds for pigs (38 meals, 13 pellets/granulates) to dry and/or wet sieve analysis. The amount of particles passing the finest sieve (or being soluble) was estimated by the difference to the total dry matter weighed prior to sieving. Mean particle size was calculated based on the weighted average of the material retained on the sieves (MPSsieves), and additionally with accounting for this lost material (MPStotal). Dry sieve analysis of the meals yielded MPSsieves of 0,58-2,90 mm and MPStotal of 0,58-2,89 mm; only 0,02 to 2,71 % of the dry matter passed all sieves. Wet sieve analysis of all meals and pellets yielded similar MPSsieves of 0,63-1,66 mm, but dramatically lower MPStotal of 0,26-1,04 mm; between 35 and 66 % of the dry matter was not retained on the sieves. Pellets had smaller MPS, and a higher proportion of particles passing all sieves than meals. Depending on the reference used, a maximum of 26 % of meals conformed to recommendations for pig feed particle size. None of the pelleted feeds met these criteria, irrespective of the source consulted for the recommendation. Wet sieving should be considered the standard analysis, because in dry sieving, very fine particles adhering to larger particles may not be registered separately but contribute erroneously to larger particle weight. In addition, the MPS calculation should account for material lost through the finest sieve. Reasons why Swiss pig feed does not meet particle size recommendations should be further investigated.

Feeding ecology of Ellochelon vaigiensis (Quoy & Gaimard, 1825) living in the Mekong Delta, Vietnam.

Ellochelon vaigiensis (squaretail mullet) adapts to a wide salt spectrum, grows quickly and is easy to raise with other species, so it is the object of attention in aquaculture. Information on the biology and ecology of the species, diet, in particular, is still scattered. Here, we explore the feeding habit, feeding intensity, and food composition of the squaretail mullet. A total of 942 fish (526 males and 416 females) were collected from November 2020 to October 2021 at four coastal sites in the Mekong Delta, Vietnam. The squaretail mullet is an algi‐omnivorous fish, as their relative gut length (1.81) falls into the range 1–3, and the diet is mostly based on algae. The feeding intensity is high due to the high value of the fullness index (4.39 ± 0.08%). The fullness index did not vary by sampling site and month, while RGL and FI changed depending on sex. Bacillariophyta (49.13%), detritus derived from organic matter (30.37%), and Cyanophyta (18.39%) are the dominant food items in the diet composition of E. vaigiensis, in which detritus is the most important food with the highest IRI index. Besides, Euglenophyta (1.00%), Chlorophyta (0.95%), Paramecium (0.06%), Copepoda (0.04%), Rotatoria (0.03%), Polychaeta (0.02%), and Cladocera (0.01%) are also recorded and ranked based on their biovolume. Some differences in diet composition are observed between immature and mature at different seasons and their interactions. Our results increase the knowledge about the feeding ecology of squaretail mullet and can help the sustainable management of this commercially important fish species.

Food spectrum and analysis of Indian shad Rastrelliger kanagurta from Visakhapatnam coast, Andhra Pradesh

Indian mackerel, Rastrelliger kanagurta is one of the commercially vital pelagic fish in east and west coast of India. The present study was analysis the food spectrum of R. kanagurtaat different stations of Visakhapatnam coast, i.e., Station 1. Bangarammapalem, Station 2. Rambilli and Station 3. Bheemunipatnam from July 2016 to June 2017. This species was found to be mainly feed on zooplankton goes to 37%, phytoplankton 26%, fish egg and larvae 10.5%, shrimp larvae 11% miscellaneous matter 9% and semi-digested matter 5.5% in case of males and females goes to zooplankton was 36%, phytoplankton 25%, fish egg and larvae 11%, shrimp larvae 11.5% miscellaneous matter 9.5% and semi-digested matter 7% was observed in this study. The study clearly explains that the R. kanagurta is a plankton feeder. The present results showed that majority of the guts are empty and range goes to 31-55%, followed by ¼ full was 11-26%, ½ full was 10.5-19%, ¾ full goes to 8-14%, full was 6-13.4% and gorged ranges between 2.5-8.5% in males in different months. In females it was showed that mostly are empty and ranges between 32-51%, followed by ¼ full was 15-30.5%, ½ full was 10.9-19.2%, ¾ full was 8-15%, full was 6-14% and gorged goes to 2.5-6.2% in study period. The feeding intensity was higher during August in case males and females and poor feeding during May and June and remain months are moderate feeding was noticed.

Deciphering the Dynamics of Reproduction and Diet for Bigeye Ilisha (Ilisha megaloptera) from the Saurashtra Coast, Northeastern Arabian Sea

Ghosh, S. and Vase, V., 2022. Deciphering the dynamics of reproduction and diet for bigeye ilisha (Ilisha megaloptera) from the Saurashtra coast, northeastern Arabian Sea. Journal of Coastal Research, 38(5), 1050–1060. Coconut Creek (Florida), ISSN 0749-0208. With no exhaustive information available for Ilisha megaloptera, the present study aimed at elucidating the reproductive and feeding dynamics from 764 individuals landed by gillnetters at Veraval, India, in the northeastern Arabian Sea. Standard length ranged from 18.4 cm to 35.2 cm. Growth was isometric in males and negatively allometric in females. Sex ratio (F:M) was 1.22, with significant dominance of females at most size classes. Maturity sizes for females and males were 24.21 cm and 24.92 cm. Observation showed that Ilisha megaloptera spawned throughout the year with major and minor peaks occurring from February to May and November to December, respectively. The monthly percentage contribution of spawning females and males ranged from 16.0 to 72.22 and 22.22 to 73.68, and the gonadosomatic index for females varied between 3.59 and 7.68. Absolute fecundity ranged from 22,875 eggs to 121,013 eggs. Asynchronous ovarian development with three distinct modes in egg distribution indicated multiple spawning events. Feeding intensity was low, with 26.05% exhibiting part-full stomachs and 7.20% full stomachs. Feeding activity was lowest during spawning peaks and highest in fishes measuring 26.0–29.9 cm. Below 22.0 cm, feeding was solely on zooplankton, dominated by copepods. Feeding henceforth was mostly on nekton: crustaceans (39.35%) and teleost juveniles (38.72%). Ontogenetic shifts and seasonal variations in prey signified optimal foraging. Precipitation and salinity significantly impacted the monthly gonadosomatic index and predator–prey weight ratio. The present study provides a detailed report on bionomics for Ilisha megaloptera and could contribute to the management of Ilisha spp. stocks in the Indian Ocean, considering the paucity of information available for other species in this genus.

Feeding ecology of Amblychaeturichthys hexanema in Haizhou Bay based on linear mixed model

Many traditional economic marine fishery resources have been declining in the coastal waters of China. Amblychaeturichthys hexanema has become one of the dominant species in Haizhou Bay and some other coastal areas of China, playing an important role in marine food webs. We analyzed the feeding strategy of A. hexanema based on the bottom trawl surveys conducted in the Haizhou Bay and adjacent waters in spring and autumn of 2011 and 2013-2016. The feeding habits and main influencing factors of A. hexanema were studied using linear mixed model (LMM). The results showed that A. hexanema fed on 14 prey groups, with Amphipoda, shrimps, Bivalvia and Ophiuroidea as the main prey groups. A total of 37 species were identified in the preys. The dominant prey species were Gammarus sp., Leptochela gracilis, Monoculodes sp., Moerella iridescens and Alpheus distinguendus. Results of the linear mixed model showed that the feeding intensity of A. hexanema in Haizhou Bay was influenced by body length, water depth, survey season, and bottom water salinity. Among them, water depth and bottom salinity had significantly negative effects, whereas the impact of body length was significantly positive. The feeding intensity was significantly higher in spring than that in autumn. Results of cluster analysis showed that A. hexanema had different feeding habits between two length groups as divided by a threshold of 70 mm body length. The change of feeding habit was mainly attributed to the variations in predation ability and food availability. Feeding strategy analysis showed that trophic niche of A. hexanema had large components between phenotypes and low intraspecific competition for prey. This study would contribute to our understanding of life history characteristics and ecological habits of A. hexanema, and provide scientific support for the sustainable utilization and management.

Seasonal impact of scavenger guilds as taphonomic agents in central and northern Ontario, Canada.

The process of human decomposition is driven by biological decomposers, mainly bacteria, vertebrates, and invertebrate scavengers. When vertebrate scavengers have access to a body, they can considerably accelerate decomposition through consumption of soft tissue and dispersal of skeletal elements. Presently, there are limited data available on vertebrate scavenging activity in Canada, particularly in densely populated provinces such as Ontario. This study aimed to determine which vertebrate species belong to the scavenger guilds in central and northern Ontario, and the impact of season and habitat on these taphonomic agents. Seasonal trials were conducted in summer, fall, and spring of 2020/2021 with pig carcasses placed in open (grassland) and closed (forest) sites. Vertebrate scavenger activity was recorded continuously using cellular and non-cellular trail cameras. Photographs were analyzed to identify species, quantify feeding intensity, and document scavenging behavior. We identified four mammalian scavengers, namely coyote, red fox, fisher, and pine marten, and three avian scavengers, namely bald eagle, turkey vulture, and American crows/northern ravens (grouped as corvids) across the trials. Season impacted scavenger presence with feeding and loss of soft tissue occurring more quickly in the summer, followed by spring and fall. None of the scavengers demonstrated a clear preference for the open versus closed sites. Our findings have identified the most prevalent vertebrate scavengers in central and northern Ontario and their taphonomic impact on soft and hard tissues. It is important to consider these agents and their ability to degrade and disperse remains during the search and recovery of human remains.

Deployment of hydroacoustic feeding control in salmon sea-cages; biological and technical considerations

Automation of feeding control for sea-caged Atlantic salmon is important to reduce waste feed. Hydroacoustic appetite-led feeding, or echofeeding, uses echo sound to monitor fish biomass in a defined feeding area. As the fish become satiated and begin to leave the feeding area, the monitored biomass falls, enabling the setting of threshold levels of biomass at depth. Software then decides to continue or stop feeding. Here, we implemented a fully autonomous echofeeding system in 3 sea-cages with salmon during summer (900 g, ~14 °C) and winter (5300 g, ~5 °C). To find the best signal of feeding activity, fish biomass was monitored with two echo sounder transducers at different depths and echo beam widths, directed upwards towards the feeding area. Prior to echofeeding, we trained salmon to consume their daily ration in short, intense feeding bouts. The fish adapted to consume their daily food ration in just 1 h and sustained their feeding activity close to the surface under the echofeeding regime. The feeding response was positively correlated with feeding intensity and was strongest at the surface (0–1.5 m), with a narrow echo beam from 8 m depth giving the best proxy of fish appetite. Appetite varied between meals and days, yet echofeeding prevented waste feed while fish maintained strong growth rates. Echofeeding is simple to deploy, as farmed salmon, independent of fish size or season, can adapt to changes in feeding regimes. Both feeding intensity and the biomass threshold for feeding cessation were kept static under echofeeding, which challenge the industry's standard manual feeding control practice where feeding intensity is adjusted by visually assessing appetite within meals. Our results provide novel insight into basic principles for hydroacoustic-based and autonomous feeding control in general and highlight echofeeding as a promising technology.

Nematicidal Activity of Organic Food Additives

Organic food additives are popular in various spheres of human activity: the food industry, agriculture, veterinary and human medicine, the chemical industry, and other sectors. Due to the relatively short time of their breakdown in the environment, their non-toxicity to various organisms in certain concentrations, and their large annual amounts of production, application, and influx into the environment, it is an important task to study their influence on ecology. To help reduce toxic pressure on the environment, we studied the influence of 32 organic food additives on larvae of the nematodes Strongyloides papillosus, Haemonchus contortus, Muellerius capillaris, which are parasites of the digestive tracts of ruminants. This article presents the results of in vitro studies of organic food additives (acetic, propionic, lactic, sorbic, adipic, fumaric, malic, citric, ascorbic, and dehydroacetic acids, sodium formate, calcium formate, potassium acetate, calcium acetate, sodium diacetate, calcium propanoate, sodium lactate, potassium sorbate, sodium sorbate, calcium sorbate, trisodium citrate, monosodium glutamate, sodium dehydroacetate, sodium benzoate, potassium benzoate, calcium benzoate, biphenyl, dibutylhydroxytoluene, hexamethylenetetramine, 2-phenylphenol, natamycin, and nisin) on nematode larvae at various stages of their development. Propionic acid and 2-phenylphenol, used in the food industry, exerted notable nematicidal effects on larvae of S. papillosus, M. capillaris, and H. contortus: 1% concentrations of the substances killed 85% of these larvae, except H. contortus, which were tolerant to 2-phenylphenol in 52% of cases. Other tested food additives at 1% concentrations could not kill more than 70% of invasive nematode larvae in 24 h. The research determined various degrees of toxicity of the studied substances to invasive (third age) and non-invasive (first and second age) larvae, which are related to a decrease in the feeding intensity of parasitic nematodes on the stage of third age larvae. Thus, some organic food additives, introduced into the environment with food wastes, are able to affect the vitality of certain nematode species to a varying extent.

Assessing trophic interactions among three tuna species in the Solomon Islands based on stomach contents and stable isotopes

Trophic research is essential to the conservation and management of fishery resources. This study analyzed the feeding habits and nutritional interactions among three tuna species in the waters of the Solomon Islands (5°12′S–15°20′S, 157°31′E–172°19′E). A total of 103 bigeye tuna (Thunnus obesus), 296 yellowfin tuna (Thunnus albacores), and 264 albacore tuna (Thunnus alalunga) samples were collected from September to December 2019. Samples for stomach content and stable isotope analysis were randomly selected. The stomach content analysis results showed that the stomach contents of the three tuna species were rich in prey, and 48 prey species were identified, including fish, cephalopods, and crustaceans, with high between-phenotype component (BPC). Yellowfin tuna consumed the largest variety of food and bigeye tuna consumed the smallest. The feeding intensity of bigeye tuna were higher than that of yellowfin and albacore tuna. Yellowfin tuna had the highest empty stomach rate (35.69%) and lowest average stomach fullness index (0.064). The degree of stomach fullness in the three tuna species was mainly 1, and the difference in the stomach fullness index among them was significant (P<0.001). Food overlap (0.3–0.6) and Levins index (<0.6) among the three species were low, indicating a specialized feeding tendency. Bigeye tuna mainly feed on Ommastrephes bartrami and Myctophidae, yellowfin tuna mainly feed on Hyperiidea and Aluterus monoceros, and albacore tuna mainly feed on Gempylus serpens and Loligo chinensis. The stable isotope results showed that the δ13C and δ15N values of the three tuna species were significant (P<0.001). The standard ellipse area corrected for small sample sizes (SEAc) and total niche area (TA) of bigeye tuna, range of δ15N (NR) of yellowfin tuna, and range of δ13C (CR) of albacore tuna were the highest. The results of this study will help improve our understanding of the feeding ecology of these three tuna species and their important roles in the ecosystem and food web structure.

Food and feeding habits of Sardinella longiceps Valenciennes, 1847 caught along Veraval coast of Gujarat

This study is based on the examination of gut contents of 351 specimens of Sardinella longiceps Valenciennes, 1847landed at Veraval Harbour, Gujarat. Feeding intensity of S. longiceps was reduced during spawning season andgradually increased during post-spawning period. The fish was found to be a planktivorous species consuming diatoms, dinoflagellates, zooplankton and unrecognisable matter. Diatoms were the most dominant group followed by zooplankton and dinoflagellates. Unrecognisable matter comprised of mud, detritus and sand particles were observed in the stomach of S. longiceps throughout the study period. Index of preponderance values showed that the diatoms (57.17%) and zooplankton (36.51%) were the major components of the diet. Keywords: Arabian Sea, Diet analysis, Indian oilsardine, Trophodynamics

Food composition and feeding strategies of an invasive species, Carassius gibelio (Bloch, 1782) inhabiting a eutrophic lake in Middle Black Sea region

Diet composition and feeding features of the Prussian carp Carassius gibelio (Bloch, 1782) were studied by analysing the stomach content of 155 fish specimens sampled from Lake Ladik during November 2009-October 2010. Five of the specimens had empty stomachs. A total of 29 prey taxa belonging to eight major groups comprising aquatic insects, Copepoda, Cladocera, Rotifera, Bacillariopyhta, Chlorophyta, Cyanobacteria and fish eggs were identified in 150 full stomachs. Diet composition showed slight seasonal variation. Cladocera was the most important prey item in all seasons, with peak abndance in spring. Feeding intensity exhibited seasonal change and was maximum in summer. Summer and autumn diets of this species showed the highest similarity. The study indicated that the Prussian carp in Lake Ladik showed both omnivorous and opportunistic feeding habits, exhibiting specialised feeding strategy on Cladocera, while they showed generalised feeding strategy on most prey items. The wide dietary plasticity of invasive Prussian carp can help their population to expand rapidly in different aquatic ecosystems. Keywords: Alien species, Diet composition, Feeding habits, Lake Ladik, Prussian carp

Factors influencing food composition, feeding habits and intensity of Glossogobius giuris caught from the vietnamese mekong delta

ObjectiveKnowledge of diet composition and feeding habits are essential to our understanding of fish ecological adaptation and aquaculture studies. This study aims to gain knowledge on diet composition, feeding intensity and habits for Glossogobius giuris – a commercial goby residing in brackish to freshwater regions of the Vietnamese Mekong Delta. MethodsA collection of 1,291 samples (632 males and 659 females) were caught monthly from January 2020 to December 2020 at four sites using trawl nets. A combined analysis of prey occurrence and weight was used to calculate the diet composition of this fish. ResultsThis fish displayed high feeding intensity, and its diet composition was seen to be comprised of small fish, Acetes spp., Uca spp., molluscs, and others (e.g., detritus and fish scales). Although males and females of two fish size groups, two seasons and at the four sites displayed the same feeding trends as Costello graphical analysis showed, the diet composition was seen to vary with season and site. It suggested that the difference in salinity between seasons and the four sites regulated food composition within this fish. ConclusionThese findings advance the understanding of fish adaptation capacities and food flexibility.

Eco-biological Study of the Mosquitofish Gambusia affinis from Oubeira lake

Gambusia was studied in Oubeira lake in spring 2016. A total of 100 specimens were collected in the lake. The sex ratio was F:M = 5.12: 1. The length-weight relationship was estimated for the population, with Wt = 0.0197Lt2.4451. The condition factor was calculated C=1±0.2 (for population) and a significant difference was observed between males and females. For 100 examined stomachs, the diet mainly consists of algae (N=54.96%, Pi= 166%, O=91%), followed by the mosquito larvae (N=21.52%, Pi= 65%, O=49%), detritus (N=19.2%, Pi= 58%, O=46%) and arthropods (N=4.3%, Pi= 13%, O=13%). For mosquitoes, two genus were recorded: Culiseta and Culex with 4 species: Culex pipiens, Culex theileri, Culex laticinctus and Culex antennatus. The culture experiments confirmed the important predation on mosquito larvae was observed with feeding intensity for females and males of 86 ± 12.28 % and 92 ± 8 % for the Culex larvae and 91 ± 7 and 93.66 ± 5.68 for the Culiseta larvae, respectively. No significant difference was observed between the sexes or for mosquito larvae. Our data support the idea that the introduction of mosquitofish has both negative and positive effects since this fish feeds on the most abundant food and not only on mosquitoes.

Revealing the Effectiveness of Fisheries Policy: A Biological Observation of Species Johnius belengerii in Xiamen Bay

The rapid development of China’s economy has brought tremendous pressure to the marine ecosystem, and about 57% of marine fish populations have been overexploited or collapsed. A series of fisheries policies have been implemented successively to improve the decline of resources. Over the past decade, the fisheries sector has particularly increased focus on resource and ecosystem sustainability, which has led to the wider use of stock management policies in China. Therefore, fishery resource assessment is crucial, such as assessing the long-term changes in biological information. This study is based on biological characteristics of Johnius belengerii captured by bottom trawls in Xiamen Bay during two periods, beginning in 2006 and 2016. Length composition, length–weight relationship, growth, mortality, sexual maturation, and feeding intensity were analyzed. The changes in biological characteristics show that there is a phenomenon of improvement in the later period, of which the changes are closely related to a series of fisheries management strategies, such as setting closed fishing periods and non-fishing areas, and establishing fishery restoration marine protected areas. This result seems to reveal the effectiveness of a long-term series of fisheries policies. It can provide an important basis and visibility for management effectiveness.

Impact of fish feed formulation training on feed use and farmers' income: Evidence from Ghana

Feed accounts for 60–80% of tilapia production costs, and high feed cost and limited feed access are major issues faced by fish farmers. A potential solution is for farmers to produce their own feeds using cheaper and locally available ingredients. This paper evaluates the feed formulation training implemented in Ghana as part of the Fisheries Commission's activities under the Ghana Aquaculture for Food and Jobs program. This paper analyzes baseline and follow-up survey data using difference-in-difference estimation and analysis of covariance. One year after the training, results show positive impact on the farmers' knowledge of feed formulation, quantity of feed formulated, feeding and management practices, productivity, and income. Feed formulation training encouraged more farmers to formulate their own feeds and maintained or increased total feeds used in their facilities from 2018/2019 to 2020/21. Among the farmers who did not receive training, feed formulation activities and feed quantity used reduced from 2018/19 to 2020/21. A common practice is the use of locally available quality commercial feed as starter feed for smaller fish and own-formulated feeds as a complement for or alternative to commercial growout feeds for bigger fish. Especially when constrained by lack of funds, many farmers reduce the use of commercial feeds and formulate their feeds using cheaper and locally available raw materials to maintain similar levels of feeding intensity. Feed formulation acts as an important coping strategy in the context of small-scale farmers with limited financial resources. This study recommends scaling out feed formulation training and expanding research on optimal fish nutrition using locally available and low-cost raw materials, in combination with commercial feeds, to maximize productivity and incomes for farmers.

Determination of β -decay feeding patterns of Rb88 and Kr88 using the Modular Total Absorption Spectrometer at ORNL HRIBF

Precise determination of ground-state feeding in the β decay of fission products is an important but challenging component in modeling reactor antineutrino flux and reactor decay heat. The Modular Total Absorption Spectrometer (MTAS) is a versatile NaI(Tl) detector array that determines the true β-decay pattern free from the pandemonium effect, including precise ground-state feeding intensities. In this paper, we report MTAS results of the β feeding intensities of Rb88 and Kr88, fission products with large cumulative yields in nuclear reactors. By comparing MTAS results with previous measurements, Rb88 provides a validation of MTAS's ability to determine ground-state feedings in β decays, while the precision of Kr88 ground-state feeding is improved when compared with the Evaluated Nuclear Structure Data File (ENSDF). The investigation of sources that contribute to β feeding branching uncertainties in MTAS experiments is discussed in detail. Lastly, the deconvolution of Rb88 decay spectra suggests that MTAS can distinguish an allowed β spectral shape from a first forbidden unique β spectral shape.1 MoreReceived 29 October 2021Accepted 15 April 2022DOI:https://doi.org/10.1103/PhysRevC.105.054312©2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBeta decayNuclear structure & decaysProperties59 ≤ A ≤ 89TechniquesNuclear data analysis & compilationSpectrometers & spectroscopic techniquesNuclear Physics

Effects of breed and fattening system on fatty acid and chemical composition of meat from male lambs

The purpose of this study was to examine the fatty acid and chemical composition of the Longissimus dorsi (LD) from male Tuj and Hemşin lambs reared in extensive, semi-intensive and intensive feeding systems. At the end of 90 days eight lambs from each breed and feeding system were slaughtered to determine chemical composition, and six lambs in each group were selected at random to assess fatty acid composition. Breed and feeding system interaction affected the quantities of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA), and the atherogenic (AI), thrombogenic (TI), and nutritive value (NVI) indices. In Hemşin the ratio of PUFA to SFA was higher in lambs fed in the extensive system than those produced in the semi-intensive and intensive systems, which were similar, whereas in Tuj this ratio decreased from the extensive to semi-intensive to intensive feeding systems. The ratio of omega n-6 to omega n-3 fatty acids was lower in the extensive and semi-intensive systems than it was in intensively fed Hemşin lambs, but increased with the intensity of feeding in Tuj lambs. Intramuscular fat content was higher in Hemşin lambs than in Tuj lambs and increased with the intensity of the feeding system. Conjugated linoleic acid content (CLA) was affected by feeding system in Hemşin lambs, but not in Tuj lambs. Because of their high PUFA/SFA ratio and low TI value, Tuj lambs reared in extensive feeding system were deemed to have the best performance.

Fish feeding intensity quantification using machine vision and a lightweight 3D ResNet-GloRe network

Quantifying feeding intensity of fish is important in developing intelligent feeding control system, thus improving feed utilization rate and reducing water pollution. The current study explored a real-time, high-precision and lightweight 3D ResNet-Glore fish feeding intensity quantification network, which can accurately locate the four levels of fish feeding intensities in video stream. In this network, the lightweight GloRe module is expanded in 3D space, and the Residual block in the 3D ResNet network is modified to form the 3D GloRe module. The relational reasoning is achieved through graph convolution in the interactive space to improve accuracy of discrimination. In addition, the sliding window and the frame extraction processing of the video data significantly reduces the model parameters and the amount of calculation. Experimental results showed that the classification accuracy for four types of feeding intensity was 92.68%, which is 4.88% higher compared with that of the classical 3D ResNet network. The parameters were decreased by 46.08% and the GFLOPs decreased by 44.10%. The proposed network improved the training and recognition speed and reduced the hardware equipment requirements, which can provide a theoretical basis for subsequent feeding decisions.

Long-term dynamics of forage base and food supply for nekton in the upper epipelagic layer of the western Bering Sea. Part 2. Food supply for nekton

Interannual dynamics of feeding conditions for nekton in the upper epipelagic layer of the western Bering Sea is considered for the summer and fall seasons of 2002–2020. In the summers, daily consumption by fish and squids ranged from 0.01 to 0.10 t/km2 in the deepwater basins and between 0.01–0.38 t/km2 in the shelf area at Cape Navarin. In the falls, the consumption increased to 0.03–0.14 t/km2 in the deep-water basins, and to 0.01–0.53 t/km2 in the Navarin area. Summary in the summer-fall periods, the fish and squids consumed 2–5 % of zooplankton production (up to 5–7 % in some years) in the deep-sea basins that is rather low degree of the zooplankton resources usage. In the Navarin area, the consumption is considerably higher and is estimated as 5 % in summer and 21 % in fall season, on average. In cases of heightened nekton biomass and reduced zooplankton biomass in some years, the grazing pressure on plankton increased, in particular on euphausiids, hyperiids and pteropods, while the intensity of salmon feeding decreased, with extension the portions of nektonic food and other zooplankton groups, as arrowworms, in their diet. On the other hand, the portion of juvenile fish and squids in the salmon diet increased in cases of high abundance of this prey, too. Weak correlation was detected both between the salmon feeding and abundance of their prey and between the salmon feeding and abundance of salmons. The feeding conditions for pink salmon during their offshore migration did not determine the rate of their returns. Strong year-classes of pink salmon had large returns in conditions of either poor or rich food supply in fall season, so the feeding in fall was not important for the pink salmon survival in the ocean in winter. Feeding of other fish and squids species did not change noticeably in the years with reduced food supply. In general, abundance and species composition of plankton and nekton communities were rather stable in the western Bering Sea in the 2000-2010s, and this current state of the ecosystem provides stable functioning of nekton communities both in the deepwater and Navarin areas.