Joo Myun Park

Ontogenetic and diel changes in diets of two sympatric mudskippers Periophthalmus modestus and Periophthalmus magnuspinnatus on the tidal flats of Suncheon Bay, Korea

Variability in the diet breadth of two sympatric mudskippers Periophthalmus modestus and P. magnuspinnatus in the tidal flats of Suncheon Bay, Korea, was compared. The analysis of 494 P. modestus and 455 P. magnuspinnatus specimens revealed that both were carnivores, consuming mainly gammarid amphipods, polychaetes, insects, and crabs. However, adult P. modestus consumed greater proportions of polychaetes whereas P. magnuspinnatus ate more crabs. The diets of both species showed ontogenetic changes in diet; smaller individuals of both species consumed harpacticoid copepods and gammarid amphipods, whereas larger fishes of both species fed mainly on different preys. The stomach content index (SCI) of both species underwent significant size-related and diel changes; the values of both species were higher in the larger size classes and during the late afternoon. Levin’s index of diet breadths of both species were lower during the day than at night, indicating high prey selection during the daytime. Non-metric multi-dimensional scaling ordination emphasized that the dietary compositions of the smaller individuals of both species showed some obvious similarities, with dietary similarity gradually reducing with increasing fish size. This indicates that the two species consume gradually different types of prey as they grow, that is, resource partitioning may be occurring between larger P. modestus and P. magnuspinnatus.

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

Abstract 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.

Seasonal variations in species composition of fish assemblage collected by trammel net in coastal waters of the East Sea

Seasonal variation in species composition and abundance of fish assemblage in the north coast (NC: Ayajin) and central coast (CC: Hupo) of the East Sea were calculated using samples collected by trammel net during 2011-2012. A total of 20 species from NC and 17 species from CC were collected. Of the fishes collected, the dominant fish species were Glyptocephalus stelleri and Careproctus rastrinus in the NC, and Dasycottus setiger and G. stelleri in the CC. These 2 fishes accounted for 71.7% and 81.0% of the total number of individuals collected in the NC and CC, respectively. The number of fish species, number of individuals, biomass and species diversity indices fluctuated with the seasons. The cluster analysis and non-metric multidimensional scaling (MDS) based on Bray-Curtis similarity revealed that the fish assemblages classified into north and central groups. Analysis of similarity percentages of species contributions (SIMPER) indicated that most individual of G. stelleri and Gadus macrocephalus contributed to north group, and D. setiger and G. stelleri in central group, whereas 15 species contributed to 90% of the dissimilarity.

Feeding Habits of the Blackthroat Seaperch Doederleinia berycoides in the Southern Sea of Korea

The feeding habits of the blackthroat seaperch Doederleinia berycoides were studied using 650 specimens collected in the Southern Sea of Korea, from January to December, 2005. The size (standard length, SL) of the specimens ranged from 6.3 to 35.2cm. D. berycoides is a piscivore that consumes mainly teleosts such as Engraulis japonicus, Acropoma japonicum, and Myctophum nitidulum. Of the fish species Engraulis japonicus was the preferred prey. D. berycoides also eats small quantities of shrimps, amphipods, euphausiids, mysids, and crabs. D. berycoides showed ontogenetic changes in its feeding habits. Smaller individuals (5-10cm SL) fed mainly on shrimp. The proportion of shrimp decreased with increasing fish size, and this decrease paralleled the increased consumption of fish. Fish accounted for almost all of the stomach contents of individuals larger than 15cm SL. Cluster analysis based on the percentage dry weight (%DW) identified two size groups: group A (<15cm SL) consumed primarily shrimp and fish; and group B (15< cm SL) preyed exclusively on fish. There was little seasonal change in the diet of D. berycoides, but shrimp constituted 41.8% of the summer diet in %W.

Feeding Habits of the Redbanded Searobin Lepidotrigla guentheri in the Coastal Waters off Gori, Korea

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 signifi cantly as the fi sh grew in size.

First insights into the function of the sawshark rostrum through examination of rostral tooth microwear

Potential roles of the rostrum of sawsharks (Pristiophoridae), including predation and self-defence, were assessed through a variety of inferential methods. Comparison of microwear on the surface of the rostral teeth of sawsharks and sawfishes (Pristidae) show that microwear patterns are alike and suggest that the elongate rostra in these two elasmobranch families are used for a similar purpose (predation). Raman spectroscopy indicates that the rostral teeth of both sawsharks and sawfishes are composed of hydroxyapatite, but differ in their collagen content. Sawfishes possess collagen throughout their rostral teeth whereas collagen is present only in the centre of the rostral teeth of sawsharks, which may relate to differences in ecological use. The ratio of rostrum length to total length in the common sawshark Pristiophorus cirratus was found to be similar to the largetooth sawfish Pristis pristis but not the knifetooth sawfish Anoxypristis cuspidata. Analysis of the stomach contents of P. cirratus indicates that the diet consists of demersal fishes and crustaceans, with shrimp from the family Pandalidae being the most important dietary component. No prey item showed evidence of wounds inflicted by the rostral teeth. In light of the similarities in microwear patterns, rostral tooth chemistry and diet with sawfishes, it is hypothesised that sawsharks use their rostrum in a similar manner for predation (sensing and capturing prey) and possibly for self-defence.

Length–weight relationships and reproductive characteristics of the crowned seahorse (Hippocampus coronatus) in eelgrass beds (Zostera marina) of Dongdae Bay, Korea

Abstract This study provides novel information regarding the length–weight relationships (LWRs) and reproductive characteristics of the crowned seahorse (Hippocampus coronatus) living along the southern coast of Korea. Specimens of H. coronatus were collected from an eelgrass bed in Dongdae Bay, Korea, during September 2006–August 2007. In total, 133 specimens were collected (76 females, 57 males) and their lengths ranged from 2.41 to 9.31 cm and 2.41 to 9.32 cm for females and males, respectively. No significant difference was observed between the sex ratio of specimens collected in this study and the theoretical 1:1 ratio (χ2-test, P > 0.05). All LWRs were highly correlated (r2 > 0.941, P < 0.001), and the overall slopes of the length–weight regressions were 3.067 for females, 2.808 for males and 2.955 for both sexes. Size at first sexual maturity was 6.93 and 7.33 cm in length for females and males, respectively. Monthly changes in the gonadosomatic index (GSI) indicated that the spawning period was from June to November. Total number of eggs ranged from 56 to 163 with mature eggs from 4 to 56, and the number of brood in the pouches of males ranged from 12 to 46.

Diet composition of juvenile Korean piscivorous chub, Opsariichthys uncirostris amurensis in the surf zone of Nakdong river estuary, Korea

The diet composition of juvenile Korean piscivorous chub, Opsariichthys uncirostris amurensis were studied using 277 specimens collected from January to December 2004 in the surf zone of Nakdong river estuary. The size of Opsariichthys uncirostris amurensis ranged from 2.6 to 9.1 cm in standard length (SL). Opsariichthys uncirostris amurensis was carnivore that consumes mainly amphipods and insects. Its diet also included small quantities of polychaetes, fishes, and algae and plants. Opsariichthys uncirostris amurensis showed ontogenetic diet change. Smaller individuals (

Diets and Resource Partitioning among Three Sympatric Gurnards in Northeastern Tasmanian Waters, Australia

AbstractDietary niches can support the coexistence of closely related sympatric species in marine systems, which can lead to the presence of greater abundances of those species that can potentially support their fisheries or greater abundances for other fish species that prey upon those species. Dietary relationships for three species of gurnard (Family Triglidae) that occur together in the benthic coastal environment of northeastern Tasmania, Australia (Red Gurnard Chelidonichthys kumu, Grooved Gurnard Lepidotrigla modesta, and Roundsnout Gurnard Lepidotrigla mulhalli), were examined for the presence of such dietary niches. The species are either fishery-important (Red Gurnard) or provide prey (Grooved Gurnard and Roundsnout Gurnard) for fishery-important species (e.g., Platycephalidae and Zeidae). Based on stomach content analyses, all three gurnards were shown to be bottom-feeding carnivores that consumed mainly benthic crustaceans, particularly decapods and amphipods, with teleosts also being importan...

Feeding relationships among juveniles of abundant fish species inhabiting tropical seagrass beds in Cockle Bay, North Queensland, Australia

Dietary analysis was conducted on juveniles of 10 numerically abundant fish species inhabiting tropical seagrass beds in North Queensland, Australia. Gammarid amphipods were consumed by all of the species, but their contribution to the diet of each varied. Crab larvae and copepods contributed to the diets of Leiognathus bindus, Pranesus endrachtensis and Stolephorus sp.; polychaetes and isopods were consumed by Sillago maculata burrus, Lethrinus sp., Pelates sexlineatus and Siganus canaliculatus; and Favonigobius reichei, Coris caudimacula and Arothron manilensis fed on bivalves. Seagrass and gastropods were rarely ingested by most of these fishes, but made a moderate contribution to the diet of A. manilensis. With the exception of L. bindus, the diet of each species was correlated with size: smaller species consumed copepods, crab larvae and gammarid amphipods, while larger species ate polychaetes, bivalves, isopods and gastropods. Non-metric multidimensional scaling (MDS) ordination plots emphasised the variation in dietary composition between species, and showed that this was often correlated with mouth length and width of the fish—for example, species with larger mouth dimensions tended to have broader diets. These interspecific differences in dietary composition increase the number of food resources available to these fishes, thereby reducing the potential competition for resources within the fish community.