Relative Importance Value Index Research Articles

Structure and phenology characterization of four tree species of tropical deciduous forests

Objective: To determine the structural and phenological characteristics of four major tree species in the tropical deciduous forests. Design/Methodology/Approach: To determine their structure, ≥ 10 cm wide trees were registered at a height of 1.30 m in 30 sites of 500 m2. For phenological purposes, seven sites were selected. The following phenological stages were evaluated: dormancy, vegetative, flowering, fruiting, and seeding. Results: Four hundred and five individuals belonging to the four species under study were found: copal ancho (Bursera copallifera (Sessé & Moc.) ex DC. Bullock), Mexican kidneywood (Eysenhardtia polystachya (Ortega) Sarg.), tecolhuixtle (Mimosa benthamii (J.F. Macbr. var. bentha-mii)), and tepemezquite (Lysiloma divaricatum (Jacq.) Macbride). Tepemezquite ranked first according to the Relative Importance Value Index. Based on the phenological characteristics observed, three species lost foliage at some time of the year and only tecolhuixtle was evergreen. Study Limitations/Implications: The results and conclusions are limited only to individuals with ≥ 10 cm in diameter. Further results can be extrapolated from this data. Findings/Conclusions: The structural and phenological features of the four species evaluated in ejido El Limón have similar characteristics to those that have been described for this type of vegetation in other locations in Mexico.

Reef Fish in the Mudflats of Kaledupa Island in Wakatobi National Park, Indonesia

Although frequently described as low-fertility or low-productivity habitat, coastal mudflats serve as important feeding grounds for fish. Many fish species from adjacent coral reefs, seagrass beds, or mangroves foraging periodically in mudflats. Because of this foraging behaviour, some local fishermen are known to utilize the mudflats to catch fish. However, the impact of this catching activities to the ecosystem has not been fully discovered. An examination of the fish community structure and levels of environmental stress had carried out in the mudflat ecosystem of the coast of Kaledupa Island in Wakatobi National Park (WNP), Indonesia. Two mudflat study sites were selected from the shore of Balasuna and Tampara villages located between mangroves and coral reefs. Data were sampled from the fish catch of local fishermen using fish fences (sero) installed in each mudflat area. Fish community structure was analyzed using diversity index and index of relative importance (IRI). ABC curves and species exploitation rate were used to assess the local environmental pressure. A total of 74 fish species were recorded from the mudflats of Kaledupa, which was found to be dominated by reef-associated fish species, comprising 63 species and accounting for 85% of the total catch. Additionally, although both sites had relatively high reef fish diversity, the obtained Clarke’s W-statistic values were approximately 0, indicating that the local fish communities presented moderate levels of disturbance. Three out of five fish species with the highest IRI values were found to be over-exploited, namely Siganus canaliculatus, Lethrinus ornatus, and Lethrinus variegatus.

Weed phytosociology in diversified soybean production systems

The knowledge of the impacts of the management practices used in each agricultural production system on the ecological interactions between commercial crops and weed populations can assist in the development of specific and sustainable integrated management strategies. This study aimed to assess weed communities in soybean in succession to second-crop corn and production systems with crop diversification in Northern Paraná State. The study was conducted during three agricultural years (2014/2017). Six treatments were setup: 1 – corn/soybean, corn/soybean, and corn/soybean), 2 – white oat/soybean, rye/corn, and wheat/soybean, 3 – oat + rye/soybean, oat + radish/corn, and congo grass/soybean, 4 – canola/corn, crambe/corn, and safflower/soybean, 5 – buckwheat/ radish/corn, bean/soybean, and buckwheat/oat/soybean, and 6 – wheat/corn + congo grass, canola/corn, and bean/soybean. The relative importance value index of each weed species and the soil cover (soil, straw, and weeds) were assessed. The experimental design consisted of randomized blocks with four replications of 300 m2 (20 × 15 m). The production systems white oat/soybean, rye/corn, and wheat/soybean; buckwheat/radish/corn, bean/soybean, buckwheat/oat/soybean; and wheat/corn+congo grass, canola/corn, bean/soybean had a suppressive effect on the species Commelina benghalensis. Euphorbia heterophylla and Digitaria horizontalis were the species most adapted to the assessed production systems. Seeds remaining from crambe and radish cultivations became volunteer plants in subsequent cultivations.

Floristic composition and potential invasiveness of alien herbaceous plant in Western Mexico

Introduction: Numbers of alien plant species are rising around the globe, but not all of them become invasive. Whereas introductions have been documented for several decades in some regions of the world, knowledge on alien species in Western Mexico is limited. Here, we study roadside vegetation along an elevational gradient, which includes a protected area. Objective: We analysed the floristic composition of herbaceous alien species, their distribution patterns, and their relationship with various environmental factors. A relative importance value index (IVI) identified the most important and, therefore, probably invasive taxa. Methods: During 2017 and 2018, roadside vegetation was documented with 4-6 transects every 300 altitudinal meters, from 0 to 2 100 m, for a total of 37 transects. Each transect consisted of five 1 m² plots. All herbaceous species were registered and alien taxa identified. A cluster analysis distinguished grouping of species based on elevation. The potentially invasive species were identified by their IVI, based on the sum of relative frequency and density values. The influence of environmental variables was analysed with a canonical correspondence analysis. Results: Most alien species were grasses; other families were represented by one or two species. The species were grouped into three main clusters. The first group included rare species, the second consisted of species restricted to higher altitudes, and the third group were tropical taxa with a distribution from sea level to medium altitudes. The most important potentially invasive species were: Urochloa maxima, Melinis repens, Eragrostis ciliaris and Cynodon dactylon, all African grasses introduced for grazing. The IVI of the species was related to tree cover, leaf litter depth and surface stone cover for some species and, for others, to soil compaction, distance to major roads and elevation. Conclusions: The alien ruderal species clustered according to the general climate (temperate vs. tropical). Grasses of African origin are of highest concern as invasive species. Although most introductions are related to human disturbance, each species becomes dominant under certain environmental conditions. Thus, management programs must be specifically adjusted to each individual invasive alien.

OCCURRENCE OF NOXIOUS WEEDS UNDER DIFFERENT SOIL MANAGEMENT SYSTEMS

The aim of this work was to identify weed species in areas under different soil management systems. The research was carried out in the Brazilian Agricultural Research Corporation experimental area, in the 2017/2018 harvest, in the city of Boa Vista, Roraima State, Brazil. The experimental design was randomized blocks and the treatments included of five soil management systems (native vegetation, minimum tillage, no-tillage, conventional tillage and conventional tillage with crop rotation). Weed collection, identification, counting and drying were performed and then the phytosociological indices (Relative density, relative frequency, relative abundance, importance value index, relative importance value index and dry mass) were calculated. Variance analysis with means compared by Tukey test (P <0.05), group analysis by hierarchical and non-hierarchical method, and principal component analysis were performed. Correlation coefficients of the variables were estimated. No and minimum tillage systems had the lowest weed rates per square meter. The botanical families Poaceae, Fabaceae and Rubiaceae are the most representative in the studied systems. Concerning relative frequency, the species Cyperus flavus stood out in all treatments other than native vegetation.

Heavy metal pollution assessment in a mangrove ecosystem scheduled as a community reserve

Heavy metal pollution is one of most toxic pollutions and cause serious threat to organisms as well as the environment. The tremendous increase in industrialization and other anthropogenic activities magnify the rate of heavy metal pollution. The present study reveals the heavy metal pollution assessment in Kadalundi Vallikunnu Community Reserve (KVCR), a scheduled community reserve of Kerala, India. The results from the study indicate that the heavy metal pollution index of KVCR was less because of the mangrove cover in this region. KVCR is endowed with different mangroves and it plays a significant role in controlling the heavy metal pollution and water quality. The higher Importance Value Index and Relative Importance Value Index was shown in the case of Avicennia officinalis, followed by Acanthus ilicifolius and the lowest values of these indices were observed in the case of Sonneratia alba. The less accumulation of heavy metals in the soil sediments was due to the potential of mangrove species for effective absorption of toxic metals from the soil sediments. Mangrove vegetation in the wetlands is potent phytoremediators and can play a significant role in phytoremediation of wetlands. The high BCF value of A. ilicifolius indicates its suitability for heavy metal remediation in wetlands. Eco restoration of heavy metal polluted wetlands using mangroves is a promising and sustainable solution for heavy metal pollution in such ecologically fragile areas.

Estudo florístico de plantas daninhas em cultivos de melancia na Savana de Roraima, Brasil

The municipality of Bonfim is the second largest watermelon producer in the state and the incidence of weeds is as one of the factors that most affect the quality and crop productivity. The objective of this work was to study floristically weeds in watermelon crops in the municipality of Bonfim, in Roraimense savannah. The survey was conducted in 10 properties with an area of around 40 ha commercial planting watermelon. To collect the weeds used a square cast iron with dimensions of 0.50 x 0.50 m, being released randomly in the area. They were identified to genus, species, family and botany class. the phytosociological parameters were calculated: frequency, density, abundance, relative frequency, relative density, relative abundance and relative importance value index. There were also evaluated the life cycle, growth habit, propagation method and the photosynthetic pathway of invasive species. The composition of the infesting weed community in the raised area was considered heterogeneous, with 17 species in 10 plant families. Families with higher incidence were Poaceae and Fabaceae. The Digitaria and Sida genres had the highest number of species. Most of the identified weed spreads only by seed have annual life cycle and the C3 photosynthetic pathway.

Geographical and climatic gradients of evergreen versus deciduous broad-leaved tree species in subtropical China: Implications for the definition of the mixed forest.

Understanding climatic influences on the proportion of evergreen versus deciduous broad‐leaved tree species in forests is of crucial importance when predicting the impact of climate change on broad‐leaved forests. Here, we quantified the geographical distribution of evergreen versus deciduous broad‐leaved tree species in subtropical China. The Relative Importance Value index (RIV) was used to examine regional patterns in tree species dominance and was related to three key climatic variables: mean annual temperature (MAT), minimum temperature of the coldest month (MinT), and mean annual precipitation (MAP). We found the RIV of evergreen species to decrease with latitude at a lapse rate of 10% per degree between 23.5 and 25°N, 1% per degree at 25–29.1°N, and 15% per degree at 29.1–34°N. The RIV of evergreen species increased with: MinT at a lapse rate of 10% per °C between −4.5 and 2.5°C and 2% per °C at 2.5–10.5°C; MAP at a lapse rate of 10% per 100 mm between 900 and 1,600 mm and 4% per 100 mm between 1,600 and 2,250 mm. All selected climatic variables cumulatively explained 71% of the geographical variation in dominance of evergreen and deciduous broad‐leaved tree species and the climatic variables, ranked in order of decreasing effects were as follows: MinT > MAP > MAT. We further proposed that the latitudinal limit of evergreen and deciduous broad‐leaved mixed forests was 29.1–32°N, corresponding with MAT of 11–18.1°C, MinT of −2.5 to 2.51°C, and MAP of 1,000–1,630 mm. This study is the first quantitative assessment of climatic correlates with the evergreenness and deciduousness of broad‐leaved forests in subtropical China and underscores that extreme cold temperature is the most important climatic determinant of evergreen and deciduous broad‐leaved tree species’ distributions, a finding that confirms earlier qualitative studies. Our findings also offer new insight into the definition and distribution of the mixed forest and an accurate assessment of vulnerability of mixed forests to future climate change.

POTENSI FAUNA AKUATIK EKOSISTEM HUTAN MANGROVE DI KAWASAN TELUK PANGPANG KABUPATEN BANYUWANGI

Mangrove ecosystem located between terrestrial and marine coastal areas are changing constantly due to human activities that affect the aquatic fauna several species of fish and non-fish. The aim of research to determine the level of importance and biodiversity index value of mangrove, analyze abundance, biomass, diversity and equity, as well as the spread of aquatic fauna mangrove forest ecosystem. Results of the study showed an index of biodiversity of mangrove flora in the medium category with a relative importance value index Rhizophoraceae and Sonneratiaceae dominate in all phases. Economically valuable aquatic fauna found amounted to 21 species of 15 families. Groups of fish fauna found bedul fish (A. caninus) have abundance and biomass as much as 975 ind at 18,299.56 gr, meanwhile the non fish fauna found werus shrimp (Metapenaeus sp.) has an abundance of as much as 1,936 ind and biomass crabs (P. pelagicus) have amounted to 13,609.38 gr associated in mangrove areas Pangpang Bay. Fauna biodiversity index included in the medium category, meanwhile the index of evenness fauna belonging in the high category. Dispersal patterns at the mouth of the bay with the mouth of the river flow Wagut fauna found in the form of pelagic and demersal fish such as family Mugilidae, Clupediae, Leiognatidae, Psettodidae. At the center of the edge of the bay in the form of aquaculture ponds found that pelagic fish group Centropomidae, Polynemidae, Sillagidae family. Meanwhile, at the end of the bay with the river flow Setail found the group that demersal fish Platycephalidae and Gobidae family.

Feeding spectra and activity of the freshwater crab Trichodactylus kensleyi (Decapoda: Brachyura: Trichodactylidae) at La Plata basin

BackgroundIn inland water systems, it is important to characterize the trophic links in order to identify the ‘trophic species’ and, from the studies of functional diversity, understand the dynamics of matter and energy in these environments. The aim of this study is to analyze the natural diet of Trichodactylus kensleyi of subtropical rainforest streams and corroborate the temporal variation in the trophic activity during day hours.ResultsA total of 15 major taxonomic groups were recognized in gut contents. The index of relative importance identified the following main prey items in decreasing order of importance: vegetal remains, oligochaetes, chironomid larvae, and algae. A significant difference was found in the amount of full stomachs during day hours showing a less trophic activity at midday and afternoon. The index of relative importance values evidenced the consumption of different prey according to day moments. Results of the gut content indicate that T. kensleyi is an omnivorous crab like other trichodactylid species. Opportunistic behavior is revealed by the ingestion of organisms abundant in streams such as oligochaetes and chironomid larvae. The consumption of allochthonous plant debris shows the importance of this crab as shredder in subtropical streams. However, the effective assimilation of plant matter is yet unknown in trichodactylid crabs.ConclusionsThis research provides knowledge that complements previous studies about trophic relationships of trichodactylid crabs and supported the importance of T. kensleyi in the transference of energy and matter from benthic community and riparian sources to superior trophic levels using both macro- and microfauna.

Diet shift response in round goby,Neogobius melanostomus, based on size, sex, depth, and habitat in the western basin of Lake Erie

Summary This study examines the diet of the round goby (Neogobius melanostomus) in the western basin of Lake Erie. As an invasive benthic feeder, the round goby has the potential to affect smallmouth bass and other native species. Round goby (n = 100) were collected during summer 2011 and stomach contents were examined to determine diet patterns and possible ontogenetic diet shifts. Individual round goby were grouped by sex, size (small 5 m), and habitat type (natural shallows, anthropogenically modified shallows, and deep waters). Gut fullness ranged from 10 to 100% with 23 stomachs presenting 100% fullness. Round goby consumed 27 different food items including abiotic (sand grains, gravel), floral (algae, fine leaved vascular plants), and fauna items. The Index of Relative Importance (IRI) and comparative z-tests were used to assess correlations and differences. Two-way z-tests revealed a significant difference in mouth gape related to size (z = −5.56377, P = 2.64e-08), and habitat depth (z = 3.34262, P = 0.00083). A significant linear correlation was also found between mouth gape standardized by head length (HL) for both males (P = 2.63e-9) and females (P = 1.3e-4). Two-way z-tests also revealed a significant difference in gonadosomatic index (GSI) related to sex (z = 6.07727, P = 6.11248e-10), but not size. A significant difference in gut fullness was also found related to sex (z = −3.34743, P = 0.00082), habitat depth (z = 3.16336, P = 0.00156), and habitat type (z = −2.7398, P = 0.00615). IRI values demonstrated a diet selective of veliger mussels (IRI = 2462.01), juvenile mussels (IRI = 1073.03), cladocerans (IRI = 4804.31), and chironomids (IRI = 1012.12). While previous studies have focused on round goby diet shifts from macroinvertebrates to bivalves, most studies did not evaluate changes in diet among multiple categories. Furthering knowledge of multiple aspects of goby diet may aid in developing management techniques to deter future round goby invasion.

Seed rain dynamics following disturbance exclusion in a secondary tropical dry forest in Morelos, Mexico

In most of the legally protected areas in Mexico local inhabitants use natural resources, such as fire wood or cattle grazing. These frequent but low-intensity disturbances have consequences at various levels of the tropical ecosystems and strongly impact forest structure and its regeneration capacity. Despite their importance, the effects of these perturbations in many aspects of tropical forest ecology and in the forest's capacity to recover after disturbance exclusion remain poorly understood. Understanding the impact of these processes on tropical forests is necessary for rehabilitating these forests and enhancing their productivity. In this study, we evaluate the impact of twelve years of exclusion (E) of cattle grazing and fire wood extraction in the composition and dynamics of seed rain, and compare this assessment to a similar analysis in an area where these perturbations continued (without exclusion, WE). We found a strong seasonality in seed rain (96% of seeds fell in the dry season) in both areas. There were no significant differences between E and WE sites in relation to overall seed density, species richness and diversity. However, the distribution along the year of seed species density was significantly different among the E and WE sites. The Jaccard's similarity index between E and WE sites was relatively low (0.57). Barochory was the most common dispersal mode observed among the 23 species in terms of seed species density (48%), followed by anemochory (39%) and zoochory (13%). In relation to seed density, anemochory was the most frequent dispersal mode (88%). Most species in the zone were categorized as small seeds (92%), and there were no significant differences in the distribution of seed size between E and WE. The spatial pattern of dispersal of the four species with the highest relative importance value index, in both areas, was aggregated. Twelve years of disturbance exclusion were not enough to fully restore the seed rain of the area; some differences were already perceptible after this lapse. On the other hand, zoochorous species were almost absent from both sites. The re-introduction of climax and animal-dispersed species may be, in addition to perturbation exclusion, a viable strategy to accelerate ecological restoration in this area.

Feeding ecology of the early life-history stages of two dominant gobiid species in the headwaters of a warm-temperate estuary

The diet and population structure of larval and early juvenile Glossogobius callidus and Redigobius dewaali (Gobiidae) were examined from the headwater region of the permanently open Great Fish Estuary along the south-east coast of southern Africa. Stomach contents of five selected size classes were sorted and identified to the lowest possible taxonomic level for each goby species. Using % Index of Relative Importance values, ontogenic shifts and dietary breadth were determined for each species as was dietary overlap between species. Numerically, both gobiid species showed similar temporal and spatial trends. Seasonal differences in catches were evident, although no numerical differences across sampled sites were found. A large degree of dietary overlap was found between the two species. The zooplanktonic diet showed a greater degree of ontogenic shift in R. dewaali than G. callidus, although similar trends were found for both. In both goby species, Calanoid sp. (Copepoda) generally decreased in importance across size classes, being the most important in the smallest size class whilst Corophium sp. (Amphipoda) increased in importance across size classes, being the least important at the smallest size classes. For both G. callidus and R. dewaali, Insecta contributed significantly to at least one of the five size classes. The larger size classes showed the least dietary overlap and the highest niche breadth. In addition, as is the case in many gobiids worldwide, the larger size classes of both sampled gobiid species consumed a broader prey size range. In conclusion, dietary overlap was largely similar between the young gobiids, suggesting that either food resources are not limiting, or niche separation is attributed to differences in foraging strategies. Ontogenic dietary shifts were however present for both gobiids with regard to prey items and prey size, suggesting a greater degree of foraging niche separation in adults of the species.

Feeding habits and ontogenetic diet shifts of hairtail, Trichiurus margarites, in the Beibu Gulf of the South China Sea

The monthly and ontogenetic variations in diet of hairtail Trichiurus margarites Li (1992) [20] (Perciformes, Trichiuridae) were examined in the Beibu Gulf of the South China Sea from October 2008 to September 2009. Stomachs of 666 hairtail ranging in size from 121 mm to 561 mm pre-anal length (PL) were sampled monthly from commercial fish catches. Fish were the primary prey, with Decapterus maruadsi (Perciformes, Carangidae) averaging 23% by number, 34% by weight, and 49% by Index of Relative Importance (IRI). Other important prey in the diet included the small benthic fish, Bregmaceros rarisquamosus and Bregmaceros nectabanus (Gadiformes, Bregmaceroridae) and the decapod shrimp, Acetes chinensis, with IRI percentages of 8%, 4%, and 3%, respectively. Low rates of cannibalism and predation on 30 additional species of prey were observed. Trophic diversity (Brillouin Index, H z ) was moderate throughout the year. Mean feeding intensity (Repletion Index, RI) varied considerably by month and increased with the gonad maturity stages of hairtail; conversely, the proportion of empty stomachs decreased with maturity stages, from 60.9% empty at Stage I to 41.6% empty at Stage VI. Prey weight and numbers differed significantly among the 14 PL size classes and increased with body size. Cluster analysis of prey IRI values also indicated differences in the feeding habits of hairtail by size class. Understanding the monthly and ontogenetic changes in hairtail diet may assist in the development and improvement of marine ecosystem modeling for the Beibu Gulf, South China Sea.

Summer feeding ecology of Great Pampa-finches, Embernagra platensis at Laguna de Guaminí, Buenos Aires, Argentina

The aim of this study was to assemble data on the summer feeding ecology of the Great Pampa-finch, Embernagra platensis at the Laguna de Guaminí, Buenos Aires, Argentina, and to explore the differences related to the dietary patterns for each sex between winter and summer when possible. The stomach contents of 43 birds were analyzed. The animal fraction was composed of Hymenoptera (45.1%), Coleoptera (32.4%), Lepidoptera (6.0%), Araneae (5%) and Orthoptera (3.2%). The application of the index of relative importance (IRI) resulted in 1490.4 for Coleoptera, 428.5 for Hymenoptera and 162.5 for Lepidoptera caterpillars. The vegetal fraction consisted of Triticum aestivum (26.9%), Cyperaceous (25%), Poaceae (Gramineae) (19.3%) and Panicum sp. (11.2%). The IRI values were 893.8 for Triticum aestivum, 174.5 for Gramineae, 126.5 for Panicum sp. and 112.8 for Scirpus sp. The food niche width was 0.33 for both sexes; the diversity index resulted in 1.06 for females and 1.33 for males and specific diversity ranged from 1.87 to 2.84. A canonical component analysis (CCA) was performed on environmental and morphometric variables, and a Monte Carlo test confirmed the canonical correlations. A t-test showed that some birds harmonized with a logarithmic model and some with a geometric curve. During the summer, Embernagra platensis ingests Hymenoptera and Coleoptera more often than seeds, suggesting that two biological mechanisms could be taking place in this bird.

COMMUNITY CHARACTERISTICS OF SHRIMPS IN THE OFFSHORE WATERS OF THE MID-SOUTHERN EAST CHINA SEA

Based on the data of the shrimp resources sampled by single trawler as investigation boat in 18 stations in the offshore waters of the Mid-Southern East China Sea (26°00'N—28°30'N,121°00'E—126°00'E) in May,August,November,2006 and February,2007,total catch from each trawler was counted and identified to species in taxonomy,and the spatial variation of the shrimp species composition,index of relative importance (IRI),the diversity and similar characteristics of the community structure were analyzed. 32 species of shrimp were caught in this survey,which belonged to 22 families under 11 genera. Comparison of the amounts of various species in different seasons:there are 22 species in the autumn which are the most; 20 species in winter,17 and 18 species in the spring and the summer respectively. According to the standard of index of relative importance (IRI) (the species with IRI above 1000 were regarded as the dominant species in this paper),there were 10 dominant species:Metapenaeopsis longirostris,Metapenaeopsis dalei,Solenocera alticarinata,Plesionika izumiae,Ibacus novemdentatu,Parapenaeus fissuroides,Solenocera koelbeli,Solenocera crassicornis,Parapenaeopsis hardwickii and Solenocera crassicornis,and 5 of them were major dominant species which were Metapenaeopsis longirostris,Metapenaeopsis dalei,Plesionika izumiae,Parapenaeus fissuroides and Parapenaeopsis hardwickii. Defined the ones with IRI values ranging from 100 to 1000 as common species,we got 7:Metapenaeopsis barbata,Penaeus japonicus,Plesionika dentirostris,Palaemon gravieri,Alpheus japonicus,Parapandalus spinipes and Sicyonia cristata. The abundance of the dominant species was varied with seasons. For example,5 were in May:Metapenaeopsis longirostris,Metapenaeopsis dalei,Parapenaeopsis hardwickii,Solenocera alticarinata and Plesionika izumiae,89.15% of the total catch and 92.14% of the total individuals. In August,there were 7 dominant species:Metapenaeopsis dalei,Plesionika izumiae,Metapenaeopsis longirostris,Parapenaeus fissuroide,Solenocera crassicornis,Ibacus novemdentatus and Solenocera alticarinata,91.82% of the total catch and 95.05% of the total individuals. In November,the number of dominant species increased to 8:Metapenaeopsis longirostris,Plesionika izumiae,Parapenaeus fissuroides,Metapenaeopsis dalei,Solenocera crassicornis,Ibacus novemdentatus,Solenocera koelbeli and Solenocera alticarinata,occupying 95.31% and 97.56% of the total catch individuals,respectively. In February,the number reduced to 5:Metapenaeopsis longirostris,Parapenaeus fissuroides,Metapenaeopsis dalei,Solenocera koelbeli and Plesionika izumiae,88.76% and 94.93% respectively. Based on their adaptability to habitats,all recorded species of shrimps were categorized into the hyperthermal and hysaline community in the Mid-Southern East China Sea. The stations with high abundance were mainly located in the west of the 120m isobaths,and gradually lower toward the autumn to winter,while it reached the lowest in winter. Margalef index (D) and Shannon-Wienner index (H') were higher in summer and autumn than those in winter and spring,Pielou's evenness index (J') in the offshore waters of the Mid-Southern East China Sea was stable through every season. The result indicated that the diversity index west of the 120m isobaths was higher than in the east. By hierarchical cluster analysis and non-metric multidimensional scaling (NMDS) assisted analyzing,the types of shrimp assemblage determined by influential factor such as aquatic system,water mass and salinity etc. in the East China Sea in spring were also discussed in the article,two main assemblages were identified in the offshore waters of the Mid-Southern East China Sea,which were deeper costal shrimp assemblage and out shelf sea shrimp assemblage.

Food habits of the longnose skate, Raja rhina (Jordan and Gilbert, 1880), in central California waters

Feeding studies can provide researchers with important insights towards understanding potential fishery impacts on marine systems. Raja rhina is one of the most common elasmobranch species landed in central and northern California demersal fisheries, yet life history information is extremely limited for this species and aspects of its diet are unknown. Specimens of R. rhina were collected between September, 2002 and August, 2003 from fisheries-independent trawl surveys. Percent Index of Relative Importance values indicated that the five most important prey items in 618 stomachs of R. rhina were unidentified teleosts (31.6% IRI), unidentified shrimps (19.6% IRI), unidentified euphausiids (10.9% IRI), Crangonidae (7.4% IRI), and Neocrangon resima (6.0% IRI). There were significant dietary shifts with increasing skate total length and with increasing depths. Smaller skates ate small crustaceans and larger skates ate larger fishes and cephalopods. With increasing depths, diet included bentho-pelagic teleosts and more cephalopods and euphausiids. The findings of this study are consistent with previous researchers that report similar diet shifts in skate species with size and depth.

Feeding Habits of Winter Flounder (Pleuronectes americanus) in a Habitat Exposed to Anthropogenic Distribution

The feeding habits of the winter flounder (Pleuronectes americanus) were examined in a habitat subjected to chronic anthropogenic disturbance by organic and inorganic nutrient disposal and shipping activity. The macrobenthic community was numerically dominated by the types of polychaetes and amphipods found in a disturbed community. Little variability was found in the diets of 151 winter flounder (100–300 mm total length) in 4 size-classes. Combining all size-classes, winter flounder were found to feed on 18 different genera of macrobenthos. Amphipods and polychaetes dominated the diet. These groups provided from 12–25% of the diet by weight, 16–48% by number, and had index of relative importance values between 552 and 2 510. Major prey items were the amphipod, Ampelisca abdita and the polychaete, Streblospio benedicti. These diets were compared to those winter flounder captured in habitats where benthic assemblages were not exposed to human perturbation. Regardless of habitat, winter flounder fed on primarily the most abundant and active benthic species. This study supports the contention that winter flounder are in general, opportunistic feeders and usually feed on the most abundant and available prey source.

The effect of a seed source on primary succession in a forest ecosystem

An analysis of the Relative Importance Value Index (RIVI) of later successional tree species and the Shannon diversity indexH′ of all tree and shrub species was undertaken on previously mined sites within a sparsely forested area in central Florida, USA. A comparative analysis of the distance to a seed source and the age of a site suggested that the distance to a seed source was the best predictor (R 2=0.85) of the regeneration of the later successional species and a good predictor of species diversity. Both theRIVI of the later successional species and the diversity index decreased with the distance from the seed source. The lack of a seed source containing climax species resulted in arrested succession at some sites. It is suggested that biological information is the causative means of succession and the dispersal of this information entails spatial dependency while its introduction and development are time dependent processes.