Habits Of Fish Research Articles

Giving a combination of Tubifex sp feed and floating pellets for the growth and survival of kelabau fish fry (Osteochilus melanopleurus, Bleeker 1852)

The research was conducted from April to August 2023 at the Fish Hatchery and Breeding Laboratory. Faculty of Fisheries and Marine Sciences, University of Riau. The purpose of this study was to determine the effect of changing Tubifex sp natural feed with floating pellets on the growth and survival of kelabau fish larvae. The method used in this study was an experimental method with one factor using a completely randomized design (CRD) with nine treatments and 3 replications. The treatments given were P1 (8 gr Tubifex sp and 2 gr floating pellets), P2 (7 gr Tubifex sp and 10 gr floating pellets), P3 (6 gr Tubifex sp and 4 gr floating pellets), P4 (5 gr Tubifex sp and 5 gr floating pellets), P5 (4 gr Tubifex sp and 6 gr floating pellets), P6 (3 gr Tubifex sp and 7 gr floating pellets), P7 (2 gr Tubifex sp and 8 gr floating pellets), P8 (1 gr Tubifex sp and 9 gr floating pellets) and P9 (10 gr floating pellets) each treatment was carried out for 10 days. The analysis used in this research is descriptive analysis. The results showed that there was an effect of combined feeding on the growth of kelabau fish as indicated by an increase in absolute weight and length. Absolute weight and length decreased when using floating pellet feed, this is suspected pellet feed is not in accordance with the eating habits of kelabau fish.

Feeding habits of the longfin goatfish Upeneus supravittatus Uiblein and Heemstra, 2010, along Chennai coast, south India

Recognising the need to understand the feeding habits of marine fishes, a study was undertaken on the longfin goatfish Upeneus supravittatus Uiblein and Heemstra, 2010, which contributed to trawl fisheries along Chennai coast (south-east coast of India). Dataon trophic attributes such as mouth gape area, gill raker counts, stomach and intestine lengths and gut condition and contents were collected and analysed to determine condition index, index of relative importance (IRI), niche breadth and trophic level (TrL) with reference to two variables, namely, body size (small, medium and large) and season (post north-east monsoon (PNE); summer (SUM); south-west monsoon (SW); north-east monsoon (NE). The mouth gape area of U. supravittatus was 129.3 mm2. The maximum body depth-total length ratio was 1:5.0; gill rakers in lower arch was 29 and the relative intestine length was 0.48. Empty stomach contributed 56.1% of the samples. U. supravittatus fed on prey belonging to 25 Orders and >40 Genera. Decapods such as shrimps and crablets were the main prey followed by fishes. The IRI of decapods was 6474 and that of fishes was only 193. The maximum prey size predated by the fish was 33.5 and 9.8% in terms of the predator’s length and weight, respectively. Higher prey diversity was noticed in small size group and during south-west monsoon season. The narrow niche breadth of 0.20 showed the selective nature of the fish to feed on decapods. The fish is a benthic carnivore with a mean trophic level of 3.58. The trophic level decreased with body size. Diet similarity was evident between north-east and post north-east monsoon and between summer and south-west monsoon seasons. Diversity indices showed marginal variation in prey diversity among size groups and among seasons. This study paves way for estimating production efficiency of U. supravittatus. Keywords: Diet composition, Index of relative importance, Trophic level, Trophic morphology, U. supravittatus

Biogeographical diet variation within and between the rabbitfishes Siganus corallinus, Siganus doliatus, Siganus trispilos and Siganus virgatus.

Feeding habits of herbivorous fishes play an important role in shaping the form and function of coastal marine ecosystems. Rabbitfishes (Siganidae) are important consumers of macroalgae on Indo-West Pacific coral reefs. However, it is unclear how their diet varies among and within species at biogeographical scales, casting doubt on their precise functional roles across different regions. The present study assessed the inter- and intra-specific diet variation of four rabbitfishes (Siganus trispilos, Siganus corallinus, Siganus virgatus and Siganus doliatus) factored by morphological relatedness among populations from Ningaloo Reef (western Australia), the Great Barrier Reef (GBR, eastern Australia) and the Yaeyama Islands (Okinawa Prefecture, Japan). Results showed that the region had a strong effect on diet, effectively reducing the expected effect of morphologic similitude. While intra-specific differences were only significant when populations inhabited different regions; interspecific differences were not as predicted, with different morphotypes having similar diets when populations inhabited the same regions. Rabbitfishes consumed more corticated and filamentous macroalgae on the GBR, more foliose and membranous macroalgae at the Yaeyama Islands, and more leathery macroalgae at Ningaloo Reef. The findings indicate that rabbitfishes have high diet plasticity, and hence their functional role as mediators of competition between macroalgae and corals can change across biogeographic regions. Local context is therefore important when assessing the diet and functional role of herbivorous fishes. As climate change unfolds, shifts in the distribution, trophic behaviour and function of species are expected, making the study of trophic plasticity more important.

Probing into the impacts of endogenous and exogenous short chain fatty acids (SCFAs) in fish health and growth

Abstract Short-chain fatty acids (SCFAs) are small organic acids exist in the fish gastrointestinal tract, mainly acetate, propionate, and butyrate. These SCFAs are produced through anaerobic fermentation of dietary non-digestible carbohydrates by gut microbes. Though enough studies have been devoted to showcasing the potential of SCFAs in human nutrition, the research on their production, potential, and existence in fish has been comparatively limited until recently. This review aims to provide a comprehensive overview of the current knowledge regarding SCFAs in aquaculture. It starts with commenting on the different sources, such as substrate and microbial species that are responsible for the production of SCFAs and their transportation and ends up depicting the relationship between biofloc technology and SCFAs production. This review also discusses the factors influencing SCFA production, such as environment, diet, and feeding habits of fish. Furthermore, the biological functions of SCFAs have been highlighted, and critical findings were compiled, including immunomodulatory effects, physiological response, gut health, and immunity.

Growth And Food Habits Of Pelian Fish Tor Douronensis Caught Using Tuba Root Poison In Krayan Nunukan, North Kalimantan

The use of semah fish with the local name pelian fish in nature is carried out using various methods, one of which is using tuba root plant poison. This tuba root poison is thought to have an impact on the biological condition of pelian fish and aquatic ecology. In connection with this, this research aims to analyze the size distribution, growth type and food habits of pelian fish. The research was conducted from June to August 2023 in West Krayan District, Nunukan Regency, North Kalimantan. The results of the study showed that the length distribution of pelian fish caught using tuba root plant poison was 30.626 ± 7.048 cm, with a weight of 786.531 ± 430.066 g. The growth pattern is negative allometric with eating habits consisting of moss at 44.57%, insects at 33.04%, pieces of fruit at 10.00% and unidentified at 12.39%. Moss and insects are the main food, while fruit is a complementary food. Based on the results obtained, pelian fish in nature can be caught using moss bait. The use of high doses of tuba root can cause damage to the fish's gills, which can cause fish death as a result of not being able to neutralize rotenone.

Review of methodologies for detecting an observer effect in commercial fisheries data

Observers are deployed on commercial fishing trips to collect representative samples of discard rates. However, fishers may change their fishing habits when an observer is onboard (“observer effect”) or observer programs may over- or under-sample portions of the fleet (“deployment effect”). If the extent of these effects are substantial, observer data will not be representative of unobserved trips, potentially biasing the estimation of discards. This sampling bias can impact catch monitoring, stock assessments, and fishery management. The purpose of this study was to examine the power and error rate of several published methods for detecting an observer effect using a simulation of observer and deployment effects at varying sampling ratios (i.e., observer coverage) for several sample statistics. The simplest methods (t-test and F-test for difference of means and variances) provided an accurate although imprecise estimate of the observer effect size, but only when there were no deployment effects. A generalized linear mixed effects model (GLMM) was also not reliable for detecting small bias, but was not confounded by deployment effects and was relatively robust to changing coverage rates. The most complicated tests involved comparing differences in trip characteristics between subsequent trips for observed-unobserved and unobserved-unobserved pairs. These tests were able to detect smaller observer effects and were not confounded by deployment effects, but were unreliable at high coverage rates (>60%), producing both high false positive and false negative rates. Sensitivity tests also showed differing detection accuracy as the distribution of the metric of interest changed. Thus, the optimal test for detecting an observer effect will depend on the metric of interest, the coverage rate, and whether a deployment effect exists. An example from the New England groundfish fishery is provided to illustrate how conflicting results may be explained. Results should always be considered carefully when declaring that an observer effect is or is not occurring because of the sensitivity of the tests.

Description of a large specimen of Paralepis elongata (Brauer, 1906) from Angola, southeastern Atlantic Ocean (Aulopiformes: Paralepididae).

The elongate barracudina, Paralepis elongata (Brauer, 1906), received limited attention in the past, with only a few individuals documented, mostly in publications focusing on the feeding habits of large predatory pelagic fishes. Furthermore, the taxonomic history of the species is complicated, with some earlier sources providing incorrect information that influenced subsequent works. As a result, the accurate distribution range of P. elongata remains uncertain. An adult male specimen of P. elongata, representing the largest known individual, is reported from off Angola, southeastern Atlantic. A detailed description is provided, and the literature records of the species are reviewed and discussed.

The Research and Comparison of Fish Habits of Consumption in Tunceli (Pertek and Çemişgezek) and Elazığ (Keban and Sivrice) Districts

Bu araştırma, Elazığ ili Keban ve Sivrice ilçeleri ile Tunceli ilinin Pertek ve Çemişgezek ilçelerinin balık tüketim alışkınlıklarını tespit etmek için yapılmıştır. Bu araştırma, anket uygulaması ile yapılmıştır. Anketler, 2021 yılının Nisan-Haziran aylarında yüz yüze görüşme ve online anket metoduyla yapılmıştır. Araştırma sonuçlarına göre, bu çalışmanın katılımcıları en çok Pertek ilçesinden, en az Çemişgezek, ilçesinde bulunan katılımcılardan oluşmuştur. Ankete katılan katılımcıların en çok kesimi kırmızı eti, en az kesimi balıketini tercih ettikleri tespit edilmiştir. En fazla balık tüketimi, Pertek ve Keban ilinde olduğu gözlemlenmiştir.

Food habits of fishes in salt marsh estuaries in the western Seto Inland Sea, Japan

Food habits of fishes in salt marsh estuaries in the western Seto Inland Sea, Japan

Dependence of element composition of bile of freshwater and marine fishes on some abiotic and biotic factors

IntroductionThe elemental composition and physical properties of fish bile is a very important marker for ecotoxicological and physiological studies as bile is able to accumulate elements from environmental compartments. In the present study we focused on the effects of long term (seasons and years) and spatial distance (different water bodies) as well as other biotic (feeding habits, fish species, gut morphology) and abiotic (water salinity) factors on element composition of bile of 429 individuals belonging to 22 forms/species of fishes.MethodsElement composition was determined using an inductively coupled plasma optical emission spectrometry. The fishes were analyzed from one marine (the Kandalaksha Gulf of the White Sea), two freshwater oligotrophic (Teletskoye and Baunt lakes), and one freshwater eutrophic water body (Chany Lake). In parallel, we have estimated the volume and density of bile from the same fishes using an automatic pipette and electronic balance.Results and discussionBased on fish bile density and volume data, we hypothesize that gastric fish species (those fishes that have a stomach) require a low volume of bile, but with higher density if compared to agastric fish species (those lacking a stomach) that mainly possessed large volumes of bile, but with a lower density. We have found that the concentrations of the following Na, K, Ca, Mg, S, P (major elements) and Al, Cu, Fe, Sr, Zn (trace elements) were the highest among the 28 elements studied. There were significant findings to contribute to a better understanding of the physiology of bile. First, we have determined the conditions formed in a water body in a given year (season) are more important for element composition of fish bile rather than other tested factors (feeding habits, gut morphology, etc.). Second, the feeding habits of fishes (carnivorous compared to non-carnivorous) had a significant effect based on differences among several elements. Third, the clear distinction between marine and freshwater fishes was found only for K and Na. Understanding which elements are produced as part of waste elimination and those that are present as a consequence of vital biological functions could improve the ecotoxicological study of bile as a marker of heavy metal contamination.

Food Habits of Snakehead, Channa Striata (Bloch), in Aquatic Habitats: a Review Literature

Snakehead fish as a fish of high economic value is currently still caught through nature where cork maintenance has not been widely done. Snakehead fish contains high protein, good for health can also for recover damaged. This investigation intends to produce findings from earlier research into the feeding patterns of snakehead fish (Channa striata) in aquatic environments. Because it can serve as a resource for the public and other parties in terms of ecological and biological studies as well as serve as a guide for activities involving the farming of snakehead fish, this study literature is fascinating to address the feeding habits of snakehead fish (Channa striata). Fish fries are the principal diet for carnivorous snakehead fish. when zooplankton or other tiny crustaceans are more commonly consumed by snakehead fish larvae. This disparity in eating patterns is determined by things including fish kind, age, food availability, environment, and fish size. Due to the lack of food, the effects of the season, and the time spent searching for food, snakehead fish are found to have an empty stomach in both their larval and adult stages.

An Evaluation on Fish Diet Composition Studies in Türkiye

Determination of the dietary composition and feeding habits of fish is important to explore and compare trophic interactions, food web structure, population, and ecological dynamics within and between aquatic ecosystems and to ensure sustainability. Factors such as global warming in the world and the effects of human activity cause the reduction of fish populations to the deterioration of the ecological balance. That is why we need to fill scientific knowledge gaps to discover and protect biodiversity. In this study, studies that determine the dietary composition of fish species distributed in our country's waters were brought together and the methods used were examined. When we examine these studies; It has been observed that information on the diet compositions of threatened and important commercial fish species is lacking, and existing studies are concentrated in certain areas. It has been determined that the studies carried out in the Black Sea and Aegean Seas are more than in the Mediterranean and Marmara Seas, there are no studies in the Southeastern Anatolia region, and there are few studies in the inland waters of the Mediterranean, Marmara, and Aegean regions.

An improved 3D fish habitat assessment model based on the graph theory algorithm

With the economic development, social progress and the increase in power demand, the number of water conservancy projects has gradually increased. However, the reservoir dams inevitably lead to changes in the river connectivity and hydraulic characteristics of rivers, causing damage to fish habitats. Regulating the operation of dams to supplement the ecological flow required by fish is usually an effective way to protect river fish habitats. Based on the graph theory algorithm, we proposed an improved three-dimensional habitat model that comprehensively considered the quantity and quality of fish habitat and used it to the effect assessment of water conservancy project construction on fish habitat. The fish habitat quality evaluation indicators in this paper mainly emphasized the pivotal role of core habitat patches and the connectivity between habitat patches, namely, habitat importance index (HII) and habitat connectivity index (HCI). Then, the model was combined with the Instream Flow Incremental Methodology (IFIM) and applied to the habitat assessment of Schizothorax prenanti (S. prenanti) in the Anshunchang reach of the Dadu River. The results showed that the change trend of the habitat index curves of different water depths showed a trend of first increasing and then decreasing, but the inflection points of the curves and the habitat indexes of different water depths were different. Taking into account the bottom living habits of target fish, the most suitable flow range for S. prenanti was from 271.7 m3/s to 489.1 m3/s. Compared with previous studies, the improved three-dimensional habitat model effectively avoids simulation errors caused by ignoring habitat quality and differences in fish habits.

The feeding habits of small-bodied fishes mediate the strength of top-down effects on plankton and water quality in shallow subtropical lakes

The proliferation of small-bodied fishes in lakes is often accompanied by deterioration of water quality and ecosystem function. However, the potential impacts of different types of small-bodied fish species (e.g., obligate zooplanktivores and omnivores) on subtropical lake ecosystems in particular have been overlooked mainly due to their small size, shorter life spans and lower economic value. Therefore, we conducted a mesocosm experiment to elucidate how plankton communities and water quality respond to different types of small-bodied fishes, including a common zooplanktivorous fish (thin sharpbelly Toxabramis swinhonis) and other small-bodied omnivorous fishes (bitterling Acheilognathus macropterus, crucian carp Carassius auratus and sharpbelly Hemiculter leucisculus). During the experiment, the mean weekly total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (CODMn), turbidity, chlorophyll-a (Chl.α) and trophic level index (TLI) values were generally higher in treatments where fish were present compared to treatments where fish were absent, but responses varied. At the end of the experiment, phytoplankton abundance and biomass and the relative abundance and biomass of cyanophyta were higher while the abundance and biomass of large-bodied zooplankton were lower in the fish-present treatments. Moreover, the mean weekly TP, CODMn, Chl.α and TLI values were generally higher in treatments with the obligate zooplanktivore, thin sharpbelly, when compared to treatments with omnivorous fishes. Also, the ratio of zooplankton to phytoplankton biomass was the lowest, and the ratio of Chl.α to TP was the highest in treatments with thin sharpbelly. Collectively, these general findings indicate that an overabundance of small-bodied fishes can have adverse effects on water quality and plankton communities and that small-bodied zooplanktivorous fishes likely induce stronger top-down effects on plankton and water quality than omnivorous fishes. Our results emphasise that small-bodied fishes should be monitored and controlled if overabundant when managing or restoring shallow subtropical lakes. From the perspective of environmental protection, the combined stocking of different piscivorous fish species that feed in different habitat types could be a way forward to control small-bodied fishes with different feeding habits, but more research is needed to assess the feasibility of this approach.

On the trophic role of pelagic fishes and fishery landings shifts in the South Brazil Bight

Knowledge of the feeding habits of pelagic fishes off the Brazilian coast is scarce, making the analysis of trophic interactions often inaccurate. Here, we investigated the diet and trophic role of 12 pelagic fish species by revisiting samples obtained by the ECOSAR II Program (FURG/IO/IBAMA) between 23°S and 28°40'S, an area also known as South Brazil Bight. In addition, we analyzed their biomass and fisheries landings in order to examine shifts over time. The content of 432 stomachs was analyzed at the lowest taxonomic level possible. The frequencies of occurrence were used to cluster species, revealing three trophic guilds: "Planktivorous Clupeiformes", "Planktivorous Carangiformes", and "Piscivores". Most Carangidae consumed mainly copepods and other small crustaceans, except Selene setapinnis which clustered in the piscivorous guild together with Scombriformes specimens. In terms of biomass, the dominance of Trachurus lathami, Sardinella brasiliensis, and Trichiurus lepturus was evident. The species' trophic levels ranged from 2.98 to 4.5, showing that these fishes occupied intermediate to high trophic position. Comparing fisheries landings in two study periods (1986-2002 and 2003-2019), six species showed a decrease, while three an increase. Correlations between landings of the Brazilian sardine (Sardinella brasiliensis) and other pelagic fishes indicate that when the former's decreases, the catch of alternative species, such as Opisthonema oglinum and Chloroscombrus chrysurus, increases. The intermediate position of small pelagics in the food web may affect the availability of commercial species by controlling the abundance of lower and upper trophic-level organisms. These findings fill essential gaps for ecosystem modeling, suggesting that ecosystembased fisheries management should address multispecies issues of the pelagic realm rather than only singlespecies approaches. Combining past survey data with yield trends provides evidence for both natural and humaninduced ocean changes.

Food and Feeding Habits of Fishes in Brunei Bay, Malaysia

The study of the food and feeding habits of fishes is crucial in understanding their ecology. Food and feeding habits of the 30 fish species belonging to 22 families from Bukit Sari and Awat-awat of Lawas in the Bay of Brunei were studied on 11th February 2020 and 12th February 2020 respectively. Samples were collected using “Kabat” nets, casting nets, and seine nets. The dietary components of each species were studied and expressed as a percentage of numerical composition (N), percentage of weight composition (W), and percentage of frequency of occurrence (F). Diet compositions of the species were estimated using the Index of Relative Importance (%IRI) and trophic level (TROPHj). The major food and their Index of Relative Importance (%IRI) showed the highest was shrimps (64.25%) followed by crabs (11.78%), zooplankton (6.94%), fish (6.91%), algae (4.21%), plants (1.48%), mollusks (1.01%) and others below 1.0%. TROPHj value ranged from 2.0 to 4.2 and the trophic level value of 25 fish species was carnivorous, followed by 2 species (detritivorous and herbivorous) respectively, and 1 species (piscivorous). The findings of the study may offer important data for developing management plans for the region's fishing resources.

Assessing the geographical distribution of carnivorous and planktivorous fishes in the western Bay of Bengal

There is a clear distinction in the feeding habits of fishes between the northeastern and southeastern Arabian Sea (west coast of India) — the north is carnivorous, and the south is planktivorous —, but such a distinction is not available for the western Bay of Bengal (BoB; comprising the east coast of India and the coasts of Sri Lanka and Bangladesh). We address this question by using publicly available landing data of finfishes for the four Indian states (Tamil Nadu, Andhra Pradesh, Odisha, and West Bengal) located along the western boundary of the BoB. Our analysis shows that the southwestern BoB is rich in fisheries and is more planktivorous compared to the northwestern BoB, which is more carnivorous. North–south variability exists even within the group of fishes such as anchovies and carangids. The meagre landing information for Sri Lanka and Bangladesh suggests that they show planktivorous and carnivorous characteristics of the southwestern and northwestern BoB, respectively. We show that monthly data and clarity on where the fish were caught are necessary to link the climatic conditions to the fishery along the western BoB. The landings on the Arabian-Sea and Gulf-of-Mannar part of the Tamil Nadu coast must be separated from the landings on its BoB coast. This separation can not be done with existing landing data and should be the first step in analysing fisheries data from the western BoB. The challenges in delineating the distribution of finfishes using available data illustrated here deliver guidance for future data collection and analysis at higher spatial and temporal scales for sustainable fisheries resource management in the region.

Potential of microplastics participate in selective bioaccumulation of low-ring polycyclic aromatic hydrocarbons depending on the biological habits of fishes

Currently, although the cumulative effects of microplastics (MPs) and organic pollutants (OPs) in the environment and within organisms are being investigated, whether and how MPs participate in bioaccumulation of OPs based on a carrier effect is still unclear. In the present study, water and aquatic organisms were collected from the Pearl River. Polycyclic aromatic hydrocarbons (PAHs) and MPs were separated by solid phase extraction and were measured by gas chromatography mass spectrometry and Fourier transform infrared spectroscopy, respectively. Higher PAH concentrations at the river outlet and higher MPs abundance in the inner river were observed, indicating a mismatched distribution between PAHs and MPs. No correlation between MP abundance and PAH concentration in fishes was detected, implying that MPs exerted limited influence on PAH concentrations. Interestingly, bioconcentration factors of one major low-ring PAH (phenanthrene) in fishes showed a significant correlation with MPs abundance, implying that although MPs did not affect the variation in PAH concentrations, they potentially participated in selective bioaccumulation of PAHs. Moreover, significant correlations between MPs abundance and PAHs in fishes with different feeding and living habits were found, indicating that MPs' participation in PAH bioaccumulation was dependent on fish biology and life history. Furthermore, the health risk posed by PAHs in fishes at the river outlet surpassed the line of potential high risk, while the ecological risk posed by MPs at the inner river was in the danger category, indicating the ecological risks posed by PAHs and MPs are uneven along the Pearl River. These findings deepen our understanding of the underlying mechanism of MPs participating in selective bioaccumulation of low-ring PAHs in fishes based on fish biology and point out the present risks posed by these two pollutants in the Pearl River and its estuary, which contribute to aquatic environmental protection and fishery production in this region.

Feeding frequency has a determinant role in growth performance, skeletal deformities, and body composition in the Mexican pike silverside (Chirostoma estor), an agastric short-intestine fish (Teleostei: Atheriniformes)

Several fish species with potential for aquaculture diversification possess agastric short-intestine anatomical configuration. The absence of a stomach or long intestine in fish may imply specific feeding frequency strategies for optimal growth. Because adequate feeding frequencies are paramount for thriving fish culture, the present study aimed to evaluate the effects of feeding frequency on growth performance, feeding efficiency, survival, deformities, proximate body composition, and muscle growth in Mexican pike silverside (Chirostoma estor: Atherinopsidae) a short-intestine agastric fish. Fish with an average weight of 180.57 ± 3.02 mg were randomly distributed in twelve tanks and fed four (M4), eight (M8), and twelve (M12) times a day until apparent satiety for 45 days. Significantly higher growth (70%) was found in M12 treatment compared to M4. There was no difference in survival among treatments. However, significantly fewer deformities were found in the M12 treatment compared to M8 and M4 treatments. Increased feeding frequency produced fish with higher lipids, with a concomitant reduction in ash content. Muscle fiber diameters were significantly different in all treatments: M12 (32.97 ± 3.13 μm), M8 (30.28 ± 4.59 μm), and M4 (26.74 ± 4. 42 μm). These results reflect the importance of feeding strategies in accordance to fish habits and their digestive configurations and may be relevant for other emerging species with similar digestive morphology and lower in the trophic chain, which are essential for aquaculture diversification and sustainability.

Food habits of fishes in a subtropical seagrass bed in Nagura Bay, Ishigaki Island, southern Japan

AbstractRecent losses of seagrass beds have resulted in a decrease in seagrass-associated fishes, highlighting the need for the improved management of such habitats and resources. Analyses of feeding patterns of fish associated with seagrass habitats are useful for understanding their habitat dependence, which contributes to achieving their effective conservation. The gut contents of 61 fish species were examined to clarify the food habits of subtropical seagrass fishes in Nagura Bay, Ishigaki Island, southern Japan. A cluster analysis based on dietary overlaps showed that the seagrass fish assemblage comprised six trophic groups (small crustacean, large crustacean, detritus, plant, fish and zooplankton feeders). Small and large crustacean feeders were the most abundant, followed by detritus, plant and fish feeders. Zooplankton feeders were represented by only two species. Ontogenetic changes in food preference were recognized in four species, including Lutjanus fulviflamma, Ostorhinchus ishigakiensis, Gerres oyena and Siganus fuscescens. Small individuals of the four species generally fed on small crustaceans or detritus, subsequently switching to other larger prey items with growth (e.g. crabs, shrimps and seagrass fronds). The most important food items for the assemblage comprised harpacticoid copepods, shrimps, crabs and detritus, representing high cumulative gut volumes for all fishes. Some species showed diets remarkably different from those determined for fishes in other seagrass beds off a nearby neighbouring island, evidence of the food-use patterns of seagrass fishes varying on a small spatial scale. Such dietary flexibility may increase the adaptability of fishes to seagrass beds characterized by significant variations in available food resources.