Ontogenetic Changes In Feeding Habits Research Articles

Feeding ecology of Engraulis japonicus based on stomach contents and stable isotope

Engraulis japonicus, an important fishery resource, is a key species in ecosystem trophodynamics studies. In this study, we examined stomach content of E. japonicusby stable isotope analyses, with samples collected from the East China Sea in 2008-2009 and 2020. The aim of this study was to demonstrate their diet composition, diel and ontogenetic changes in feeding habits and trophic level. Results of the stomach content analysis showed that E. japonicus mainly fed on planktonic crustaceans and small fish. The main prey species were Euphausia pacifica [index of relative importance (IRI)=87.6%; frequency(F)=57.6%], Paracalanus parvus (IRI=3.2%, F=15.3%), and Themisto gracilipes (IRI=2.1%, F=13.1%). Results of the stable isotope analysis showed that Copepoda were the main food source of E. japonicus, followed by Euphausiacea, and the contribution rate of Amphipoda was the least, which was less than 1%. There was significant diel change in diet composition. Feeding intensity was higher in the daytime than at night, with the highest in the dusk and the lowest at midnight. Ontogenetic change in feeding habit occurred when fork length reached 90 mm, over which the fish fed both zooplankton and small fishes. The δ13C of E. japonicus was between -21.66‰ and -18.14‰, with an average of (-19.92±0.86)‰. The δ15N of E. japonicus ranged from 4.07‰ to 10.78‰, with an average of (8.14±2.48)‰. Both δ13C and δ15N values were positively correlated with fork length. Trophic level of the fish was 3.4 with stomach content analysis and 2.7 with stable isotope analysis. The results would provide important reference for understanding nutritional status of pelagic small fish, and offer some basic data to establish ecopath model.

Feeding Ecology of Padogobius nigricans (Canestrini, 1867) and P. bonelli (Bonaparte, 1846) in Aggia River (Umbria, Italy) and Their Diet Overlap

The Arno goby Padogobius nigricans is an endemic species to Central Italy. The populations of this species are in sharp decline due to habitat modifications and potentially competition with Padanian goby Padogobius bonelli, an endemic species to Northern Italy, introduced in some watercourses of Central Italy. The purposes of this paper were to analyze dietary composition of the two species, determine the degree of overlap in their diets and investigate the feeding ecology of P. nigricans in terms of absence and presence of the alien species. Specimens were collected from the Aggia River, a tributary of Tiber River. Gut contents were analyzed and prey items were identified to the lowest recognizable taxa and counted. All the obtained results showed that P. nigricans and P. bonelli in the Aggia River share a similar diet. Both species fed extensively on Chironomids and no statistically significant ontogenetic changes in feeding habits were found. A high degree of diet overlap was observed. Diet of P. nigricans and P. bonelli also included fish and where the species live in syntopy, individuals belonging to Padogobius genus were found in stomach, suggesting that mutual predation may occur.

Ontogenetic changes in feeding habits of northern elephant seals revealed by δ15N and δ13C analysis of growth layers in teeth

Stable isotope analysis is useful for examining the feeding strategies of mammals. Isotopes in the annual deposition growth layers of dentine in teeth permit assessment of ontoge- netic dietary shifts in individuals, because this metabolically inert tissue is not resorbed after deposition. Profiles of stable isotope ratios of nitrogen (δ 15 N) and carbon (δ 13 C) from the teeth of northern elephant seals Mirounga angustirostris, aged between 1 and 11 yr, were described from stranded individuals in San Benito and Magdalena Islands, Mexico, between 2000 and 2009. δ 13 C and δ 15 N values differed with age in each sex indicating shifts in feeding habits throughout life, as well as in their physiological condition. Although steady δ 13 C values within each individual sug- gest fidelity to feeding grounds, differences in δ 13 C values between males and females were likely a reflection of sexual segregation on the feeding areas, which begins during the juvenile stage. Mean δ 15 N values of males (18.3‰) and females (18.2‰) would suggest that both groups feed at a similar trophic level; however a combination of differences in benthic versus pelagic and longi- tudinal foraging habitats would be masking real sex differences in trophic level, estimated for the species at 4.6. δ 15 N and δ 13 C values varied markedly between individuals of the same sex, sug- gesting the potential existence of diverse feeding strategies leading to a resource partitioning in this species. The alleged fetal growth layer has a δ 15 N value 1.8‰ higher than the average of the adult female stage, suggesting that the fetal layer is more likely the product of the intensive nurs- ing during the first month of life.

Feeding ecology of three tonguefishes, genus Cynoglossus (Cynoglossidae) in the Seto Inland Sea, Japan

Feeding ecology was compared among the three tonguefishes Cynoglossus abbreviatus, C. joyneri and C. robustus, collected from Seto Inland Sea, Japan, from June 2000 to May 2001. They are benthivores, consuming mainly gammarid amphipods, shrimps, crabs, gastropods, bivalves and ophiuroids. C. abbreviatus consumed greater proportions of ophiuroids whereas C. joyneri and C. robustus ate more amphipods and shrimps. While C. abbreviatus consumed mostly ophiuroids in all size classes, the diets of C. joyneri and C. robustus showed ontogenetic changes in feeding habits; smaller individuals of C. joyneri and C. robustus consumed gammarid amphipods, whereas larger C. joyneri ate shrimps and gastropods, and larger C. robustus fed mainly on gastropods, crabs, bivalves and polychaetes. Cluster analysis based on diet similarities emphasized that the three Cynoglossus species could be categorized on a size-related basis into three feeding groups: smaller C. joyneri and C. rubustus (<25 cm TL) could be classified as group A, and the larger of them (>25 cm TL) as group B, whereas C. abbreviatus was categorized as group C. This means that some degree of resource partitioning can occur among the three Cynoglossus species. The seasonal changes in the diets were also significant for the three Cynoglossus species.

고리 주변해역에서 출현하는 꼬마달재 (Lepidotrigla guentheri)의 식성

The feeding habits of the redbanded searobin Lepidotrigla guentheri were studied using 186 specimens collected from September to November, 2006, in the coastal waters off Gori, Korea. The sizes of L. guentheri ranged from 7.1 to 16.7 cm total length(TL). L. guentheri is a bottom-feeding carnivore that consumes mainly shrimp, especially Leptochela sydniensis, amphipods, and crabs. Its diet also includes small quantities of stomatopods, mysids, cumaceans, euphausiids, polychaetes, and copepods. Our feeding-strategy graphical method reveled that L. guentheri is a specialized feeder, with a narrow niche width. L. guentheri mainly consumed shrimp of all size classes and did not show significant ontogenetic changes in feeding habits. Smaller individuals(7-11 cm TL) secondly consumed amphipods, with the portion of amphipods in the total diet decreasing as body size increased. Prey size increased significantly as the fish grew in size.

Feeding habits of ocellate spot skate, Okamejei kenojei (Müller &amp; Henle, 1841), in coastal waters of Taean, Korea

The feeding habits of Okamejei kenojei were studied using 592 specimens collected in the coastal waters of Taean, Korea from April 2008 to March 2009. O. kenojei is a bottom-feeding carnivore that consumes mainly shrimp, fishes, and crabs. Its diet also includes small quantities of amphipods, mysids, cephalopods, euphausiids, copepods, isopods, and polychaetes. The total length (TL) of individuals in this study ranged from 8.2 to 49.0 cm. Cluster analysis based on %IRI (index of relative importance) identified three size classes. Group A (< 20 cm TL) ate primarily caridean shrimp and amphipods; group B (20–30 cm TL) ate exclusively shrimp; and group C (> 30 cm TL) ate penaeoidean shrimp, fishes, and crabs. O. kenojei showed ontogenetic changes in feeding habits. Although shrimps were the primary food consumed by all size groups, the proportion of shrimp in the total diet decreased and the consumption of fishes and crabs gradually increased with the body size of O. kenojei. Size of the prey organisms also increased. Smaller individuals fed mainly on small prey, such as amphipods, mysids, and small shrimp, whereas larger individuals preferred larger prey, such as larger shrimp, fishes, and crabs. The size-related diet breadth and the percentage of empty stomachs were significant; the diet breadth gradually increased with body size, whereas the percentage of empty stomachs decreased. Seasonal changes in the O. kenojei diet were not significant, but shrimp constituted 97.3% of the summer diet by %IRI. Seasonal changes in diet breadth and the percentage of empty stomachs were not significant.

해초지에서 서식하는 점줄망둑(Acentrogobius pellidebilis)의 먹이습성

Feeding habits of Acentrogobius pellidebilis collected from in an eelgrass(Zostera marina) bed from January to December 2006 were studied. A. pellidebilis ranged form 1.6 to 6.9 cm in standard length were determined. A. pellidebilis was a carnivore which consumed mainly copepods, polychaetes, and amphipods. Its diets included small quantities of isopods, seaweeds, nematods, and gastropods. It showed ontogenetic changes in feeding habits. Smaller individuals (<2.0cm SL) fed mainly on copepods. While the consumption of copepods decreased with increasing fish size, the consumption of polychaetes and amphipods were increased. Dietary breadth index was varied with fish size.

Ontogenetic changes in the feeding habits of the abalone Haliotis discus hannai: field verification by stable isotope analyses

The ontogenetic changes in the feeding habits of the abalone Haliotis discus hannai were elucidated for the first time in natural habitats using stable isotope analyses. Abalone individuals were grouped into three developmental stages: small juveniles (&lt;10 mm shell length (SL)), large juveniles (10–50 mm SL), and adults (&gt;50 mm SL). The inferences of natural diets indicated that benthic diatoms, small red macroalgae and (or) juvenile brown macroalgae, and adult brown macroalgae were the primary food sources for small juveniles (6.5 ± 1.0 mm SL), large juveniles (23.7 ± 6.1 mm SL), and adults (81.8 ± 14.3 mm SL), respectively. The changes of δ13C in abalone were similar among three sampling stations and were explained by ontogenetic changes in feeding habits. The decrease of δ13C in abalone (≤20 mm SL) indicated a transition from diatom feeding to juvenile brown macroalgae and (or) small red macroalgae feeding, whereas the subsequent increase of δ13C (&gt;20 mm SL) represented a feeding transition to adult brown macroalgae. These results prove the hypothesis of the ontogenetic changes in the feeding habits of the abalone H. discus hannai.

부산 주변 해역에서 채집된 불볼락(Sebastes thompsoni)의 식성

We studied the feeding habits of Sebastes thompsoni based on 421 specimens obtained in monthly collections between January and December 2005 in the coastal waters off Busan, Korea. S. thompsoni was a crustacean feeder, and consumed mainly shrimp and euphausiids. Its diet also included small quantities of amphipods, cephalopods, and fish. It showed distinct ontogenetic changes in feeding habits. Smaller individuals (14-17 cm standard length (SL)), mainly consumed euphausiids. The portion of these prey items decreased with increasing fish size, and larger individuals (>20 cm SL) consumed mainly shrimp such as Leptochela sydniensis.

Feeding Habits of Rudarius ercodes in a Zostera marina Bed

Feeding habits of Rudarius ercodes collected from a Zostera marina bed in Jindong Bay, Korea were studied. R. ercodes was a omnivore which consumed mainly gammarid amphipods, polychaetes and eelgrass (z. marina). Its diets also included a small amount of copepods, urochordates and caprellid amphipods. R. ercodes showed ontogenetic changes in feeding habits. Small individuals less than 2cm SL fed mainly on copepods, however, gammarid amphipods and polychaetes were heavily selected with increasing fish size. The consumption of eelgrass by R. ercodes was <TEX>$10-20\%$</TEX> all size classes. The dietary breadth of R. ercodes were varied with fish size

고리 주변 해역에서 채집된 황아귀 (Lophius litulon) 유어의 식성

We examined the stomach contents of juvenile Lophius litulon, which were collected monthly in the coastal waters of Kori, Korea from January to December, 1996. L. litulon was a bottom feeding carnivore which mainly consumed fish, euphausiids, sagittoids, and shrimp. Its diet also included small quantities of copepods amphipods, and stomatopods. It showed distinct ontogenetic changes in feeding habits. Small individuals (1-2 cm SL) mainly preyed on sagittoids and euphausiids. However, individuals eve, 3 cm SL mainly preyed on fish and shrimp.

광양만 잘피밭에 서식하는 문치가자미 (Limanda yokohamae)의 식성

Feeding habits of Limanda yokohamae collected from the eelgrass bed in Kwangyang Bay were studied. L. yokohamae (1-16 cm SL) was a carnivore which consumed mainly polychaetes. Its diets included a significant quantity of amphipods (gammarids and caprellids) as well as small quantities of gastropods and ophiuroids. L. yokohamae showed ontogenetic changes in feeding habits. Small individuals less than 4 cm SL preyed mainly on amphipods. However, polychaetes were heavily selected with increasing fish size while the portion of the diet attributable to amphipods decreased sharply. Polychaetes were the major prey organisms for all seasons. Dietary breadth of each size class shows relatively low value, and this means that L. yokohamae depends on only few kinds of food organisms.

Diet, intestinal morphology, and nitrogen assimilation efficiency in the damselfish, Stegastes lividus, in Guam

Analysis of stomach contents of Stegastes lividus revealed a shift from omnivory in juveniles to herbivory in adults. Red algae, primarily Polysiphonia spp., Gelidiopsis intricata and Ceramium spp., formed the bulk of the diet in all size classes. Foraminifera and small crustaceans were of particular importance in the diet of juveniles. Net nitrogen assimilation efficiency of field-fed S. lividus was approximately 61%, and did not vary with fish size. The net assimilation efficiencies of fish fed on Enteromorpha in the laboratory ranged from size-class means of 36–79% for nitrogen and from 29–72% for total organic material, and increased from juveniles to adults. Apparently, juveniles compensate for a lower efficiency in assimilating plant food by including a higher percentage of animal material in their natural diets. The ratios of intestine length to standard length (IL/SL) and to intestine diameter (IL/ID) increased rapidly in juveniles and leveled off in adults. The retention time for ingested food items may only be about one-half as long in juveniles as in adults. The combination of observed IL/ID ratios and estimated retention times proved most valuable in the interpretation of ontogenetic changes in feeding habits and assimilation efficiency.