High Feeding Intensity Research Articles

Spring Food Spectrum of Two Planktivores (Sardina pilchardus Walbaum 1792 and Sardinella aurita Valenciennes 1847) From the Central Algerian Coast (3° E to 4° E—South West Mediterranean Sea) in Relation to Sexes and Sizes

ABSTRACTSardina pilchardus, Walbaum 1792, and Sardinella aurita, Valenciennes 1847, are the fish most consumed by the Algerian population. Sardine has become increasingly rare in commercial fishing catches, whereas round sardinella is being sold at excessively high prices. Given the importance of trophic interactions between clupeids and the low levels of the pelagic food web (plankton and others), the stomach contents of the two species of S. pilchardus and S. aurita are studied. Samples are collected from the spring commercial fishery (April and May 2023) associated with the two main ports on the central coast (Algiers and Bou Ismail) justified by the intense trophic activity of these two predators. High feeding intensity (or stomach vacuity coefficient) is recorded in both males and females. Our results support the hypothesis that the diet of species in specific zones remains consistent due to stable local trophic resources. This is underscored by the lack of variation in prey quality and quantity across size and sex in both clupeid species, emphasizing the role of these interactions within the pelagic food web. Using the morphological identification and counting technique, the preys are linked to 12 taxonomic units belonging to the zooplankton, phytoplankton, and miscellaneous communities. The analysis of the diet is carried out by classifying the prey on the basis of the frequency index (If), taking into account the sex and the size where three categories of prey are defined. Copepods are the preferred prey with rates that did not differ significantly by sex and place of origin of the two clupeids. These findings extended to secondary prey (other zooplankton and phytoplankton). Also, the composition of the diet remained homogeneous in the Gulfs of Algiers and Bou Ismail. Quantitative and qualitative results on diet composition of the two clupeids and their trophic interactions within the two target ecosystems will serve as a basis for fisheries management (i.e., Ecosystem Approach to Fisheries Management [EAFM] and Ecosystem‐Based Fisheries Management [EBFM]). The modeling of all the variables will allow decision makers to predict the level of exploitable biomass in the medium and long term.

Seasonal and Spatial Variation in the Diet of Gambusia holbrooki in Different Water Bodies of Karaburun Peninsula (Western Türkiye)

The Eastern mosquitofish Gambusia holbrooki Girard, 1859, has been widely introduced into tropical and temperate countries as a biological agent to control mosquitos, which are associated with diseases such as malaria and yellow fever. However, the species exhibits invasive characteristics by competing with native species for food and habitat use. This study investigates the feeding ecology of G. holbrooki populations from three distinct freshwater environments (Lake Iris, Eğlenhoca Reservoir, and Parlak Reservoir) on the Karaburun Peninsula (North-Western Türkiye), a region outside its native range. The primary aim was to evaluate seasonal and spatial variations in the diet of the species. A total of 871 specimens were analysed: 247 from Iris Lake, 318 from Parlak Reservoir, and 306 from Eğlenhoca Reservoir. Low percentages of empty stomachs (≤20%) across all populations indicate high feeding intensity. The results reveal that G. holbrooki exhibits a generalist feeding strategy, consuming a wide range of food items such as insects, zooplankton, and plant material across all the investigated environments. The relative importance of food groups (determined by the Importance Index, MI%) varied seasonally but not spatially. In all three populations, the most important food source in the spring was dipterans, followed by plants in the summer and fall, and cladocerans in the winter. Plants accounted for the largest percentage of the diet in every population (MI% >65%). These findings suggest that G. holbrooki adapts its diet to seasonal food availability.

Production of organic beef from dairy bull calves in Denmark - Effect of different production strategies on productivity, carbon footprint and biodiversity estimated by modelling

Production of organic beef from dairy bull calves in Denmark - Effect of different production strategies on productivity, carbon footprint and biodiversity estimated by modelling

Microplastic ingestion and plastic additive detection in pelagic squid and fish: Implications for bioindicators and plastic tracers in open oceanic food webs

Microplastic ingestion and plastic additive detection in pelagic squid and fish: Implications for bioindicators and plastic tracers in open oceanic food webs

Uniquely preserved gut contents illuminate trilobite palaeophysiology

Trilobites are among the most iconic of fossils and formed a prominent component of marine ecosystems during most of their 270-million-year-long history from the early Cambrian period to the end Permian period1. More than 20,000 species have been described to date, with presumed lifestyles ranging from infaunal burrowing to a planktonic life in the water column2. Inferred trophic roles range from detritivores to predators, but all are based on indirect evidence such as body and gut morphology, modes of preservation and attributed feeding traces; no trilobite specimen with internal gut contents has been described3,4. Here we present the complete and fully itemized gut contents of an Ordovician trilobite, Bohemolichas incola, preserved three-dimensionally in a siliceous nodule and visualized by synchrotron microtomography. The tightly packed, almost continuous gut fill comprises partly fragmented calcareous shells indicating high feeding intensity. The lack of dissolution of the shells implies a neutral or alkaline environment along the entire length of the intestine supporting digestive enzymes comparable to those in modern crustaceans or chelicerates. Scavengers burrowing into the trilobite carcase targeted soft tissues below the glabella but avoided the gut, suggesting noxious conditions and possibly ongoing enzymatic activity.

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

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

A predatory gastropod as the potential biological control agent of the Korean invasive mussel, Mytilus galloprovincialis (Lamarck, 1819)

A predatory gastropod as the potential biological control agent of the Korean invasive mussel, Mytilus galloprovincialis (Lamarck, 1819)

Feeding habit and diet composition of Glossogobius aureus Akihito & Meguro, 1975 in the Vietnamese Mekong Delta

Feeding habit and diet composition of Glossogobius aureus Akihito & Meguro, 1975 in the Vietnamese Mekong Delta

Food spectrum dynamics of anadromous Hilsa, Tenualosa ilisha (Hamilton, 1822) inhabiting River Brahmaputra, India curtailing apprehension of food selectivity: An insight into its domestication

Food and feeding habits of Tenualosa ilisha collected from two sampling locations in Brahmaputra River, Assam, India for a period of 12 months from May 2018 to April 2019 were studied. Index of preponderance revealed semi-digested animal matter (25.92 %) as the most dominant food item followed by Bacillariophyta (23.32 %). 31 genera of phytoplankton and 15 genera of zooplankton were observed in the gut of the species. Major groups of zooplankton include cladocerans, copepods, followed by rotifers, while diatoms, green algae and blue green algae were dominant phytoplankton groups. The anadromous tropical shad is planktivorous by nature and has a preference for zooplankton in smaller size groups (< 250 mm) and phytoplankton in larger size groups (> 250 mm). GaSI values (mean±SE) ranged from 1.50±0.14 to 6.93±0.89 and HSI values from 0.58±0.06 to 1.54±0.15. Index of fullness was found to range from 7.08±0.42 to 1.81±0.40. Feeding intensity, GaSI, HSI values showed seasonal variation, found to be low during October to December and high during February to June. Size group-wise analysis of feeding intensity showed high feeding intensity in lower size groups (< 250 mm) and comparatively low feeding intensity and high percentage of empty stomachs in higher size groups (> 250 mm). RLG values ranged from 1.181±0.028 to 1.450±0.052. Monthly average RLG values were found to be highest during November and in the size group of 351 – 400 mm. Changes in food composition were noticed in both months and as well as size groups.

Diet composition, feeding dynamics and proximate composition of obtuse barracuda Sphyraena obtusata (Cuvier, 1829) in the southeastern Arabian Sea

Diet composition, feeding dynamics and proximate composition of obtuse barracuda Sphyraena obtusata (Cuvier, 1829) in the southeastern Arabian Sea

Reproductive and feeding biology of unicorn leatherjacket, Aluterus monoceros from the Bay of Bengal, Northern Indian Ocean

Abstract No prior comprehensive information on the reproductive biology and trophodynamics of Aluterus monoceros was globally available. The present study was performed on 1036 individuals landed along the western Bay of Bengal during 2017 to 2019. Length ranged between 25.3–64.4 cm in females (mean at 48.34 cm) and from 21.5–64.1 cm in males (mean at 47.83 cm). Growth was negatively allometric with no significant difference between sexes. Sex ratio (F:M) was 1.03 with variations based on sizes and months. Size at sexual maturity for females and males was 40.85 and 41.60 cm, respectively. The species spawned throughout the year with major and minor peaks during February to May and October and November. Absolute fecundity increased linearly with length and weight and ranged from 33,640 eggs to 12,39,202 eggs. Stomachs were empty or with trace amounts of food in 59.17%, part-full in 34.07% and full in 6.76% of the fishes. Stomach vacuity and fullness and predator–prey weight ratios varied with an increase in body size, implying higher feeding intensity in large-sized fishes. Feeding activity was more intense during June–August and less during the peak spawning months. The species is omnivorous and a bottom feeder. Teleosts contributed the most to the prey items (43.23% by Index of Preponderance) implying preference for carnivory. Ontogenetic shifts and seasonal variations in prey items were observed. The present study provides paramount information that can significantly contribute to the management and conservation of monacanthid stocks in northern Indian Ocean.

Production risk, technical efficiency, and input use nexus: Lessons from Bangladesh aquaculture

Abstract The optimal use of resources in aquaculture is important, especially in developing countries, to obtain the highest possible outcome from the production process to support food security and poverty alleviation. Thus, within this study, the risk, efficiency, and input‐use variation in aquaculture farms in Bangladesh is investigated using a flexible stochastic frontier model with a risk and an inefficiency function. The results reveal that feed, labor, and capital have positive and significant impacts on production. In addition, an increased fingerling density and a larger farm increase the risk, whereas the use of feed and the capital invested have the opposite effect. Access to extension services has a positive effect and increases farm efficiency. An investigation of the farm size–productivity inverse relationship reveals that this phenomenon is not applicable to Bangladesh aquaculture. In general, efficient farmers are large‐scale farmers, who use a lower stocking density but a higher feeding intensity, resulting in a higher yield. On average, farmers use less labor and feed than what is optimal. To increase efficiency and reduce risk, it is recommended that more technical knowledge on optimal input use, extension service, and capital is made available to aquaculture farmers.

Do green park characteristics influence human-wildlife distance in arboreal squirrels?

Do green park characteristics influence human-wildlife distance in arboreal squirrels?

Некоторые предварительные результаты биологических исследований в Карском море на НИС «Профессор Леванидов» в сентябре 2019 г.

Results of biological studies conducted at RV “Professor Levanidov” in September 2019 in the Kara Sea at depths of 18-533 m presented. During the research period, phytoplankton blooms were not observed, almost no meroplankton, eggs, and crustacean nauplia were found in samples. The bulk of communities was formed by copepods, euphausiid and chaetognaths, jellyfish and snow crab larvae were widely met. Increased biomass was observed in deep-water areas in the north, and minimal biomass was found in desalinated shelf areas in the south of the sea. In trawl catches among invertebrates, snow crab dominated with maximum catches in the north off Cape Zhelaniya and in the southwest near Kara Strait. Echinoderms and coral polyps made a significant contribution to benthic biomass. Maximum catches of invertebrates were recorded in deep-sea areas: in the north near Cape Zhelaniya (south of the St. Anna Trench) and southwest (south of Novaya Zemlya Trough). In trawl catches, Liparidae, Zoarcidae, and Cottidae were most species diverse. Dominant species in terms of occurrence and abundance was Polar cod with maximum concentrations recorded in the southern part of the sea off Kara Strait. Its abundance in 2019 compared to previous studies increased according to bottom trawl surveys and remained almost the same according to acoustic data. The most catches included American plaice with biomass 190 thousand tons. In the southeastern part of the sea near Yamal Peninsula, Pacific herring with a biomass of 214 thousand tons has been recorded. Increased concentrations of navaga with catches up to 115 specimens per haul were found near the coasts of Yamal Peninsula and Baydaratskaya Bay. Feeding habits of common fish species were studied. Diet composition and high feeding intensity indicated favorable forage conditions. Ontogenetic changes of diet composition of individual species were revealed. An extremely high level of Polar cod cannibalism observed.

A Comparative Study of Feeding of Three Fish Species in the Southern Part of Al-Chibayish Marsh, Iraq

Three species of fish Tigris asp (Leuciscus vorax) locally named " Shilluk "and Abu mullet (Planiliza abu) locally named "Khushani" and Blue tilapia (Oreochromis aureus) were collected from the Southern part of the Al-Chibayish marsh to study the composition of its natural food during the period from February 2014 to January 2015. Each species was divided into two-length group (1 and 2). Fishes consisted high percentage of Tigris asp food for both length groups, which reached 50% and 68% respectively. In contrast, sand and mud were of great importance in the food of Abu mullet that comprise 41% and 40% for the two length groups, respectively. The aquatic plant were most important in the food of blue tilapia at percentage of 56% and 50% for the two length groups, respectively. The highest feeding intensity (point/fish) reached by Tigris asp (11.30 and 13.50) during spring, for Abu mullet (10.52 and 8.08) during summer and autumn, whereas for Blue tilapia blue reached (14.82 and 12.66) in the spring and winter for the two length groups, respectively. However, feeding activity values differed according to month. The three species of fish showed a different specialization in the selection of their food components. The small individuals of the Tigris asp were narrowly specialized in food (0.27) while the large individuals were highly specialized (0.25), whereas Abu mullet and Blue tilapia showed narrow specialization (0.42 and 0.37) and (0.32 and 0.32) for the two length groups respectively.

Feeding of Tench Tinca tinca (Cyprinidae) in a Small Eutrophic Water Body

Data are presented on diurnal and seasonal dynamics of feeding of the tench Tinca tinca in a small eutrophic water body. The feeding spectrum of tench includes 60 taxa of aquatic invertebrates. Most of them (37 species) are chironomid larvae. The highest feeding intensity is recorded in the intervals from 6:00 to 9:00 p.m. and 12:00 a.m. to 3:00 a.m. The maximum value of the index of consumption is recorded in August; the minimum value is recorded in July. The feeding spectra of fish aged 6–7 years old differ considerably (the Morisita–Horn index) from 1 year older or younger fishes.

Seasonal pattern of population dynamics, spawning activities, and diet composition of sardine (Sardina pilchardus Walbaum) in the eastern Adriatic Sea

Monthly samples from commercial catches obtained with purse seiners operating in the Croatian fishing grounds (eastern Adriatic Sea) were collected throughout 2013, excluding January and December due to a fishing ban. Overall, 1010 sardine individuals were analyzed. Total body length ranged from 10.4 to 17.6 cm (mean ± SD: 13.9 ± 1.28 cm). Slightly larger individuals were caught during autumn at the beginning of the spawning season. Analysis of length-mass relationship showed that sardine specimens grow isometrically (b = 3.063). Seasonal oscillations of condition factor indicated that the examined specimens were in the best condition at the beginning of the spawning cycle. The analysis of stomach contents indicated that sardines preferred animal food (calanoid copepods, Oncaea spp., Farranula rostrata), although a plant component was also present (Bacillariophyceae). Seasonality was also observed in diet analysis, with diet changing in terms of feeding activity and prey quantity. The observed seasonal alternations of allometric condition factor and fullness index additionally confirmed that sardines were in the best condition at the beginning of the spawning season, for which they prepared themselves by higher feeding intensity, leading to higher storage of consumed energy.

Food availability influences postmetamorphic growth in two spadefoot toad species (genus Pelobates)

Understanding how major life history traits such as body size and mass and growth change in response to resource availability is crucial in explaining life history trade-offs. We conducted a laboratory experiment with three (high, medium and low) feeding intensity treatments using metamorphs of two spadefoot toads species,Pelobates syriacusandP. fuscus, from syntopic populations. We tested how total food consumption, final body size and mass, body mass increase, body mass and length growth rates and growth efficiency are influenced by food availability. The responses to food availability differed significantly between the species with respect to the total food consumption, body mass increase, body mass growth rate and growth efficiency (i.e. the ratio between total amount of food consumed during the experiment divided by the increase in body mass).P. syriacusmetamorphs had higher growth rates and growth efficiency thanP. fuscusjuveniles. Also,P. syriacusjuveniles responded to differences in food level by increasing growth efficiency with decreasing food levels. OverallP. syriacusseems better adapted to shortages in food availability thanP. fuscus. Our results clearly indicate that the differences in body size between the two species originate between metamorphosis and sexual maturity.

Diet and feeding strategies of mesopelagic fishes in the western Mediterranean

Diet and feeding strategies of mesopelagic fishes in the western Mediterranean

Feeding of whitefish Coregonus lavaretus pidschian (Coregonidae) in the lower reaches of the Northern Dvina River

Analysis was performed of the feeding of whitefish in the basin of the Northern Dvina River, including the tributary of the first order—Emtsa River and the middle course of the river, its delta part, and sites of the near-mouth offshore. It was established that, according to the pattern of feeding, whitefish is a euryphage with sufficiently wide food spectrum, including over 40 groups of food organisms at the level of classes, orders, families, and genera. The bulk of its feeding is formed by aquatic larvae of insects (mainly chironomid larvae), secondary food consists of mollusks, crustaceans, worms, and sponges. Changes in the feeding of whitefish depending on habitats, food biotopes, and difference with respect to years and seasons of the year, as well as on the age of fish, were revealed. Sufficiently high feeding intensity, as well as small changes in the feeding of whitefish in different years and at different sections of the channel indicate stable feeding conditions in the middle part of the Dvina basin. Food possibilities of the delta and the near-mouth offshore also satisfy trophic demands of the feeding school of whitefish.