Feeding habit of Brown trout (Salmo trutta fario) in upper parts of river Swat, Pakistan

Salmo trutta fario is the most important fish species of family Salmonidae inhibited in cool waters all over the world including the nortern parts of Pakistan. This study was aimed to find out the prey selection and feeding habits of the species. One hundred and eighty five Salmo trutta fario were captured from March 2016 to April 2017. Feeding intensity as represented by a fullness index (FI), changing with various length groups and season. Out of 185 Brown trout 24 fish stomaches were found empty. The most important and common food items of brown trout were Brachycentridae, Blepharocera, Hydropsychidae, ephemerella spp. Kruskal Wallis H-test were applied on feeding intensity groups consisting of three month group. The test statistic for K.W-H-test were (H=8.13 with df =3) had a p-value of 0.043 < (alpha=0.05 indicates favor of the alternative hypothesis of at least one difference among the feeding intensity groups. The linear relationship of N with index of relative importance and %IRI denoted by least square regression line (N = 35.2 + 22.1%IRI), shows that for 22 prey there is 1% change in IRI. The relationship between total length (mm) and fish body weight (gm) is expressed by Pearson correlation coefficient (r = 0.976), showed that total length (mm) and fish body weight (gm.) is highly correlated. Descriptive statistics are used for the stomach fullness, which shows that feeding intensity was recorded higher from March to May. A total of 2289 preys was recorded including the most common were; Trichoptera, Hydropsychidae, Brachycentridae, diptera, blepharocera, ephemerala, chironomida, honey bees, grass hopper, locust, trout egg, trochanter, plant tissue, stones were retrieved from the gut contents of brown trout. According to index of relative importance IRI% four preys represents major components of the diet. The highest IRI% was recorded in Brachycentridae (39.38%), followed by blepharocera (13.23%), Hydropsychidae (10.76%) and ephemerella spp (8.28%). The relationship between IRI and FO is (r =0.556) is moderately correlated with coefficient of determination (r2=0.31). This study will help in the development of an artificial diet for the species for better growth performance in captivity.

What’s on the Menu for the Resident Brown Trout in a Rich Limestone Stream?

Examination of brown trout seasonal diet variation and investigation of terrestrial prey importance in a food-rich stream using four indices of prey importance (number and weight abundance, frequency of occurrence, index of relative importance) revealed that aquatic prey constituted the major part of the diet (>90%) throughout the examined period. Despite Gammaridae being the most abundant in the environment, other less abundant organisms appeared to be important prey, including terrestrial organisms, with maximum consumption in September. The electivity index showed a positive selection of rare prey types; Tokeshi’s model revealed a specialist strategy for most of the population, except for those of 1+ age, who were inclining to generalist strategy. Diet diversity increased throughout April to October, and ages 1+ and 2+ exhibited a more diverse diet than older ages. Diet overlap between age classes was considerable, with less overlap observed in the later season. This pattern of differentiation in the diet of brown trout age classes and their feeding plasticity over seasonal scales, as observed in this food-rich stream, provides a starting point for further examination of this topic in streams with similar or different food richness and availability.

Diet of the rasptail skate, Rostroraja velezi (Rajiformes: Rajidae), off Piura, Peru

Batoids are among the least studied group of vertebrates and one of the most vulnerable to fishing. The rasptail skate, Rostroraja velezi, is a bycatch species in northern Peru for which there are no studies on its diet. This research aims to document the diet of R. velezi on the northern Peruvian coast and to determine if there are sex-based differences in the diet. A total of 74 R. velezi stomachs were collected, 59 of which had stomach contents. The cumulative prey curve showed reliability in the number of samples collected. According to the prey-specific index of relative importance, diet was dominated by Acanthephyra sp. (31%), other unidentified Caridea (15%), and unidentified teleosts (17%). A low significant difference in diet between sexes was found (R = 0.21, P < 0.01). The trophic position of R. velezi was 3.9 ± 0.7. This species displays bentopelagic feeding behavior and it is a secondary predator in northern Peru.

Morphological dietary composition of Antarctic toothfish (Dissostichus mawsoni) along the East Antarctic continental slope

To predict how the fishing of Antarctic toothfish, Dissostichus mawsoni , would affect the ecosystem, it is necessary to understand the species’ ecological niche. Morphological analysis of the stomach contents of 960 D . mawsoni specimens collected at depths of 946–1,600 m along the East Antarctic continental slope from December 2016 to March 2017 was used to assess dietary composition according to depth, sex, site, and size. Fishes were the most common prey item for D . mawsoni , comprising 97.8% based on the index of relative importance. Among the nine fish families consumed by D . mawsoni , Macrouridae was the dominant taxon. The size of D . mawsoni increased with depth. The dietary composition of D . mawsoni did not show significant differences by depth or sex, but did differ with site and size. D . mawsoni was the top predator in the ecosystem along the East Antarctic continental slope and can be considered an opportunistic feeder, feeding on abundant food in the environment. Therefore, additional studies of the diet of Antarctic toothfish are necessary to maintain the ecosystem structure and function in a changing environment, and the results of this study can be used as a monitoring baseline.

Evaluation of the trophic status of Sillago sihama and Sillago arabica at the south of Shatt Al-Arab River, Iraq

The present study is investigated the diet composition, feeding activity and intensity, and trophic niche breadth of two Sillaginid fish, Sillago sihama and Sillago arabica at the south of the Shatt Al-Arab River, Iraq from May 2019 to April 2020. A total of 511 specimens of fish comprised of 239 S. sihama and 272 S. arabica were used for the study. Fish length ranged from 11.7-23.7 and 13.0- 31.2 cm of the previous species, respectively. The results showed that the feeding activity and intensity influenced by months since the lowest stomach fullness occurred during the winter months. The analysis of diet for both species using the index of relative importance (IRI %) of prey items showed that the species were carnivores. The prey items of S. sihama were crabs (80.8%), shrimp (14.6%) and fish (4.6%), while the diet of S. arabica composed mainly on crabs (54.3%), shrimp (32.7%) and fish (13.0%). The overall values of feeding and vacuity indices were 40.4% and 9.5%, respectively for S. sihama, whereas 52.0% and 18.2%, respectively for S. arabica. Based on the results of trophic niche breadth indicate that S. schema is a high specialist feeder (Bi= 0.23), while S. arabica was considered a non-specialized feeder (Bi= 0.71). The study concludes that both species were carnivorous feeders, feeding mainly on crabs, shrimp and fish. S. sihama was a low specialized feeder, while S. arabica was not specialized.

Aspectos da alimentação natural de Larimus breviceps Cuvier, 1830, proveniente do litoral norte da Paraíba, Brasil

<p>The knowledge of natural fish feeding is important to understand the species feeding habits and how they interact with the environment. In addition to that, this kind of research can provide relevant data to improve the capture of these animals, considering their economy and social importance. This study aimed to analyze the food composition of Larimus breviceps specimens from the northern coast of Cabedelo city, evaluating the importance of each food item for their diet. The specimens came from the local artisanal fisheries. In laboratory, the individuals were identified, measured and dissected to remove the stomachs content and then examined. Three different analyzes were performed, percentage by frequency of occurrence, by number and by weight, then the index of relative importance (IRI%) was computed. In total, 30 stomachs were analyzed, 15 distinct food items were identified, the most representative prey were fish fragments, Copepoda, Gammaridae, Decapoda (shrimp), algal fragments and synthetic material. Given the results, the diet of this species becomes more diversified as young individuals reach the adults size, and ingest marine debris which indicates an anthropogenic impact.</p>

Swordfish Xiphias gladius diet in the Florida Straits

Swordfish Xiphias gladius inhabit the Florida Straits year-round and provide a significant role in the food web as top-level predators. However, little is known about the diet composition and thus ecological role of swordfish in Florida. This study investigated swordfish diet by analyzing stomach contents of 131 swordfish in the Florida Straits from April 2007 to December 2008. Identifiable species included 13 teleost species, 3 cephalopod species, and 1 crustacean species. Cephalopods dominated the swordfish diet by weight (72.4%) and number (69.9%), and ranked highest in importance in the diet by the index of relative importance (IRI; 81.5%). Teleosts occurred the most (99.1%) but represented the second highest importance in diet by weight (25.2%), number (26.3%), and IRI (17.6%). Illex sp. was the prey with the greatest dietary importance, followed by unidentifiable ommastrephid squids. Stomach fullness index values ranged from 0 (empty) to 8.98 (mean = 0.37). A positive significant correlation between swordfish length and prey length was found (r2 = 0.104, P = 0.037), and no significant correlations were found between swordfish weight and prey weight (r2 = –0.075, P = 0.065). This is the first study to report a comprehensive diet of swordfish inhabiting waters in the Florida Straits region and suggests swordfish may be opportunistic feeders, altering their diet when abundance or presence of prey changes.

Diet composition and neighboring prey community of the Phuping newt (Tylototriton uyenoi) in Maesa–Kogma Biosphere Reserve, Chiang Mai Province, northern Thailand

Dowwiangkan T, Chuaynkern Y, Dumrongrojwattana P, Duengkae P. 2020. Diet composition and neighboring prey community of the Phuping newt (Tylototriton uyenoi) in Maesa–Kogma Biosphere Reserve, Chiang Mai Province, northern Thailand. Biodiversitas 21: 4515-4523. The present work reports the comparison of fecal pellet prey composition of Tylototriton uyenoi from Maesa-Kogma Biosphere Reserve (Chiang Mai Province, northern Thailand) based on an analysis of its fecal pellets. Males of T. uyenoi consumed more diverse prey than those of females (53 groups of prey versus 14 groups). The analysis reveals a diverse diet of Arthropoda (Insecta, Arachnida, Diplopoda, Chilopoda, and Malacostraca), Mollusca (Gastropoda), Chordata, and conspecific eggs. Partial remnants of plant materials were also found in the pellets. The percentage frequency of prey occurrence was higher in Formicidae (21.34), Lymnaeidae (17.39), unknown snails (10.67), and Blattidae (9.881). The percentage of the relative number of preys was higher in Lymnaeidae (41.02) and Formicidae (17.17). The volumetric prey percentage was higher in Lymnaeidae (30.78), Paradoxosomatidae (19.14), and unknown snails (12.71). The index of relative importance was higher in Lymnaeidae (1,248.62), Formicidae (376.972), unknown snails (188.275), and Paradoxosomatidae (166.433). The percentage of IRI was higher in Lymnaeidae (57.128) and Formicidae (17.248). The Spearman rank coefficient (95% confidence interval test) showed a significant positive correlation (p<0.05) between prey volume and number and SVL.

Diet of the Bronze Skink Eutropis macularius (Reptilia: Squamata: Scincidae) from Thua Thien Hue Province, Central Vietnam

In this study, we examined the diet of 149 males and 147 females of Eutropis macularius from Thua Thien Hue Province, central Vietnam using a nonlethal stomach-flushing technique. The prey items of E. macularius composed of Araneae, Insecta (Blattodea, Coleoptera, Hymenoptera, Isoptera, Odonata, and Orthoptera), Mollusca (Philomycidae), and plant materials. The most important prey items were insect larvae, hymenopterans (including ants), grasshoppers, and termites, for both sexes in three populations. Plant materials were also found in the stomach of E. macularius with an index of relative importance of 7.19%, suggesting that E. macularius is an omnivorous species. However, the dominant prey categories of E. macularius were insects, including insect larvae, hymenopterans, grasshoppers, and termites, with many small, sedentary, clumped prey items. Simpson’s heterogeneity index of skinks from three populations from Bach Ma National Park as well as from Aluoi and Huong Tra districts were 10.07, 7.85, 3.94, respectively. Eutropis macularius showed significant positive correlations between mouth width (MW) and prey width (P = 0.001) and between MW and prey volume (P 0.0001). There are significant positive correlations between snout-vent length (SVL) and prey sizes consumed: between SVL and prey length, P 0.0001; SVL and prey width, P 0.0001; and between SVL and prey volume, P 0.0001. These results indicated that SVL and MW are the limiting factors on the size of prey consumed in this skink.

Reproductive biology and diet of the longtail butterfly ray Gymnura poecilura (Shaw, 1804) along western Bay of Bengal

The reproductive biology and diet of the longtail butterfly ray Gymnura poecilura is described based on 630 specimens (N = 377 females and 253 males). The mean disc width (WD) of females and males was 576.7 mm (range = 190–920 mm) and 416.3 mm (230–550 mm), respectively. Sexual dimorphism in size was seen, with the maximum size of males being only 60% of the maximum female size. The disc widths at 50% maturity (WD50) were estimated to be 506.5 mm (females) and 435.9 mm (males). The mean uterine fecundity was 3.3 (range = 1–8). The size at birth was between 190 and 220 mm WD. Year-round reproduction was indicated, due to the presence of mature males and gravid females throughout the year, neonates in multiple months and large variations in embryo size within months. Feeding intensity increased with body size. Fish accounted for 80.9% of the diet (Index of Relative Importance, IRI), followed by crustaceans (18.9%) and molluscs. The species was found to be a specialized feeder.