Repletion Index Research Articles

Evaluation of Dietary Choices and Feeding Behaviour of Pseudotholithus elongatus (Bobo Croaker) from Jaja Creek, Niger Delta, Nigeria

This study of the diets of the Bobo croaker (Pseudotholithus elongatus) in Jaja Creek, Ikot Abasi LGA Akwa Ibom State, Nigeria was conducted from November 2020 to April 2021. It was found that fed specimens accounted for approximately 60.55% and unfed specimens (empty stomach) accounted for approximately 39.44%. Crayfish was the most commonly consumed food with a frequency of 45.87% and a numerical frequency of 32.05%, while detritus was the food with a frequency of 2.75% and a numerical frequency of 1.92%. The total number of foods consumed by all fish was 156 and the number of specimens found with foods was approximately 109. P. elongatus has been identified as a vigorous omnivore based on a gut repletion index of approximately 70%, and this fish can be characterized as an active feeder.

The feeding habits of the Amur whitefish Coregonus ussuriensis in the Amur River, China

To study their feeding habits, Coregonus ussuriensis samples were collected seasonally in the Amur River, China. A total of 574 samples were collected, including 200 individuals with empty stomachs. The stomach contents of the remaining 374 samples were identified, counted, weighed, and analyzed. The results showed that the vacuity rate of Coregonus ussuriensis was 34.84% in total; the rates in summer and autumn were higher than in spring and winter. Prey items could be divided into three categories: fish, benthos, and mammals, with 62 taxonomic units. Of these, fish had the highest relative importance index (IRI), followed by benthos and mammals. Specifically, Exopalaemon modestus was the dominant species among the food species of Coregonus ussuriensis, and unidentified fish, Hydropsyche sp., Hemiculter leucisculus, Abbottina rivularis, and Saurogobio dabryi were important species. The average repletion index (RI, %) of Coregonus ussuriensis was highest in autumn (1.86), followed by winter (1.40), summer (1.26), and spring (1.02). The main food of Coregonus ussuriensis was benthos in spring and autumn, and fish in summer and winter. Cluster analysis showed that, according to the similarity level of the bait biological composition, the fork length group samples of Coregonus ussuriensis could be divided into three groups: 210–330 mm, 330–450 mm, and >450 mm. The highest IRI% of feed organisms in these three groups of samples were fish (73.67%), benthos (75.12%), and benthos (94.46%), respectively. It can be observed that with the growth of the fork length of Coregonus ussuriensis, the importance of benthos in its diet increases. The results of an RDA analysis on the relationship between main bait organisms and various factors indicated that season, river level, river width, and fish size have a significant impact on bait organisms and a positive or negative impact on the quality scores of some bait species. This study filled the gap in biological research on the feeding ecology of Coregonus ussuriensis and laid a research foundation for ecological research on this species and its resource protection and aquaculture.

Use of trophic ecology of omnivorous fish and abiotic factors as supporting tools for assessing environmental impacts in a neotropical river.

The study of diet is one of the mechanisms by which competition for resources between species that cohabit in the same ecosystem can be inferred. Therefore, the relationships of the indices that measure specialization in the diet of fish species are necessary to characterize the nutritional quality of these populations and the ecosystem's environmental health. Three species of catfish were selected: one invasive (Clarias gariepinus) and two natives (Trachelyopterus striatulus and Rhamdia quelen), with similar distribution along the Guapi-Macacu River, in the Guapimirim Protection Area (Rio de Janeiro). Fifty-nine catfish of the three species were collected in total, along 32 collection points in the Guapi-Macacu River in two periods (dry and rainy) in 2018. Non-parametric statistics showed the partition of resources between species and the influence of abiotic factors (temperature, pH, transparency, and dissolved oxygen) contributing to the selection of available resources in the environment. Diet-related indices-repletion index (RI), condition factor (K), niche width, and trophic position (TP) of the specimens collected-contributed to measuring the nutritional status of each of these catfish species, showing that R. quelen has a relationship between RI and K, tending to absorb and metabolize nutrients faster than other species. In addition, the invasive species occupies a wide range of TPs compared to native species, confirming its feeding plasticity. On the contrary, T. striatulus needs large amounts of terrestrial insects to maintain its poor condition factor. Also, the RI showed direct influences of abiotic variables, with the temperature being the most prominent. Our results suggest that the invasive species can benefit from this environment that shows signs of environmental degradation.

Effects of biological and environmental factors on the variability of Paralonchurus brasiliensis (Sciaenidae) density: An GAMLSS application

The hypothesis of this study was based on the premise that complex interactions between biological and environmental factors may explain variability in fish population dynamics. To test this, Paralonchurus brasiliensis (Sciaenidae), a keystone species associated with coastal waters, was used as a model fish species. Generalized Additive Models for Location, Scale and Shape were performed to evaluate relationships among biological and environmental variables. Fish biomass, repletion index (RI), hepatosomatic index (HSI), condition factor (K) and sex ratio was in models as biological factors whereas water temperature, salinity, organic matter, grain size and depth were included as environmental variables. The results revealed significant effects of biological and abiotic factors on population density of P. brasiliensis. The selected model explained 94% of the variability in the explanatory variables. Fish biomass, HSI and K were the most important biological factors, whereas temperature and organic matter were the most important abiotic factors. Variability in fish density suggests that HSI and K both could be used as an additional ecosystem indicator of environmental status (food availability) and fish population health. We also highlight the importance of using robust and flexible statistical methods to model fish population dynamics and the need to incorporate biological and environmental factors into fishery resource management.

Environmental, Biological, and Fishing Factors Influencing Fish Mortality and Development of the Cachirra event, Navío Quebrao Lagoon

Objetive: The present study analyzes environmental, biological and fishing factors incidence in the formation and mortality of the Cachirra event.
 Methodology: We collected samples from fishing nets used by the fishermen of "arranchaderos" community located in Navio Quebrao Lagoon (NQL). IDEAM provided 2017 climatologic data. Physicochemical variables were measured with Spectroquant SQ 118 and other direct measurement electronic devices. SPSS statistical software version 24.0 was used to analyze data and their relationships.
 Results: 12 species intervene in the formation of the Cachirra event, predominantly the Mugilidae family. Salinity was the physicochemical variable that most affected the mortality of the species -October (6.0 PSU) and March (67.4 PSU)-. Conclusions: Fishes die according to their susceptibility to salinity changes, being the most susceptible species Cathrorops spixii and Eugerres plumieri, and the most resistant Elops saurus and Mugil liza. The species present in NQL have sizes well below commercial significance and different condition factor values and repletion index values before and after the Cachirra event.

Factors influencing the feeding habits of the ghost crab Ocypode quadrata (Fabricius, 1787) on subtropical sandy beaches

Studies on feeding habits are fundamental to characterising the trophic role that species play in an ecosystem. They also help to understand the dynamics of populations involved in ecological relationships. Among the existing populations on tropical and subtropical sandy beaches in the world, the ghost crab (Ocypode) is the most conspicuous invertebrate. Despite its wide distribution, there is arguable information on the trophic ecology of this crab. Our study thus aimed to characterize the diet of the Ocypode quadrata on three morphologically distinct beaches in southern Brazil. Considering such factors as environmental differences, seasons, sex, and ontogeny, we evaluated which of these would be responsible for differences in the crab's food composition and quantity of items consumed. In addition, we used the repletion index (RI) to check the presence of food resource throughout the year. The samples were collected monthly, from March 2017 to February 2018, on three subtropical beaches in southern Brazil. We performed the biometry of the crabs, which involved weighing and measuring the size of the individuals, followed by the weighing of the stomachs to calculate the repletion index. We examined the contents of 660 stomachs, which were grouped into major food categories. Feeding index (IAi) indicates that feeding patterns varied only between seasons, demonstrating that the availability of prey is reflected in the diet of the ghost crab. The most significant items in its diet were insects, unidentified organic matter, and crustaceans. The RI tended to increase as the sand temperature increased. An increase in daytime foraging activity during cold months in contrast to a greater night-time foraging during warmer months shows a plasticity in the time of foraging. Finally, we conclude that the variety of prey consumed suggests that the O. quadrata has mainly opportunistic detritivorous feeding habits, as well as other feeding modes.

Trophic niches of two predator fish cohabiting in the Algerian coastal ecosystem: Scorpaena porcus (Linnaeus, 1758) and Scorpaena notata (Rafinesque, 1810)

The diet of adult specimens of black scorpionfish Scorpaena porcus (Linnaeus, 1758) and small red scorpionfish Scorpaena notata (Rafinesque, 1810), collected from the Algerian coast was studied using different coefficients and trophic indexes. The inventory of ingested prey indicates that the focal species have a diverse diet that covers different zoological groups. Their feeding spectrum is mainly composed of brachyuran crabs and other crustaceans such as isopods and shrimp. Fish and molluscs are only occasionally ingested. The vacuity coefficient average exceeded the estimated rate of 40%. The observed monthly fluctuations revealed a seasonal alimentary rhythm. The foraging activity of the two scorpionfish decreases in summer, during gonad maturation. This decrease is highlighted by the increase in the vacuity coefficient and the decrease in the repletion index. Despite a similarity in the food bolus, the two co-occurring fish exhibit a specialized diet. This was observed especially in mature individuals. In conclusion, our results demonstrated a very strong overlap of niches between two scorpionfish species.

Natural diet of the endemic freshwater crab Aegla castro Schmitt, 1942 (Decapoda: Anomura: Aeglidae)

Abstract We characterized the natural diet and feeding dynamics of Aegla castroSchmitt, 1942 (Aeglidae), an endemic freshwater crab. Research was undertaken on the trophic spectrum of the species by analyzing the stomach contents of individuals collected in a stream in southeastern Brazil, and evaluating the diet through the index of relative importance (IRI). Seasonal and circadian variations in diet composition were analyzed, and the feeding dynamics investigated through repletion index (RI) analysis. We analyzed a total of 240 stomachs and identified 20 main food categories of the diet, which were studied throughout the seasons. Aegla castro maintained a constant RI throughout the year, with a peak of food activity between midnight (00) and 0600. The species was characterized as an omnivorous generalist and opportunist. The high overlay in the diet composition of adults of both sexes and juveniles indicates that they share the same food resources, even though they seem to exploit them in different quantities and frequencies. Future research should focus on the species of Aegla whose diets have not yet been described, and use available data to inform trophic network analyses and models.

Temporal and spatial variability in the feeding behavior of the black sea urchin Arbacia lixula (Echinodermata: Echinoidea) from the north-western Algerian coast

The black sea urchin Arbacia lixula (Linnaeus, 1758) is one of the most domi-nant echinoids in the sublittoral communities of the Mediterranean Sea, where it is considered an essential structuring species by its grazing activity. The present work is considered to be the first study to address the diet of the species A. lixula in Algeria. This study aims to perform on the one hand; a temporal monitoring of the food preferences of two populations of A. lixula living in two different sites in shallow water (port of Salamandre, Stidia) on the coast of Mostaganem (Algeria) during the years 2015 and 2016, and on the other hand; get an idea of the variations of the different trophic sources used and appreciated by this echinoid. The quantitative and qualitative aspect is achieved by monitoring the evolution of the repletion index as well as the identification of the items present in the digestive contents by the contact method of Jones (1968). The results of this monitoring showed that it is an opportunistic species which adapts its diet according to the quality and quantity of food available. Arbacia lixula prefers encrusted coralline algae with a large faunal fraction. In areas rich in nutrients, the spines of these sea urchins may elongate to half the diameter of the test. Based on the results, A. lixula can be associated with habitat, seasonal changes or other specific environmental parameters that merit further development in order to fully understand its functioning in marine ecosystems.

Diet and histological features of digestive tube from four discarded fish species by trawl bycatch in Northeastern Brazil

Abstract: Fish feeding habit associated to the morphology of their digestive tube can provide useful biological and ecological information. Between January and December 2012, we examined 16 fish species discarded by trawl in the Potiguar basin, northeastern Brazil, and classified them into four groups according to Alimentary Index - IAi. Our aims were to: (1) provide information on diet composition of one species represented by each group (Opisthonema oglinum, Conodon nobilis, Larimus breviceps and Sphoeroides testudineus), (2) examine the morphology of their digestive tube, and (3) associate ingested food items with the morphological features. Stomach contents were collected and classified according to IAi: main, accessory and secondary categories; fragments of esophagus, stomach, and small intestine were examined using paraffin section technique. Biometric data (total length-TL, standard length-SL and total weight-TW), stomach weight-SW, and gonadal weight-GW were recorded and applied in two indices: (1) the stomach Repletion Index - SRI (SRI = SW/TW × 100) and (2) the gonadosomatic index - GSI (GSI = GW/TW × 100) for the analyses of feeding and reproductive activities, respectively. The main food categories were (1) Teleostei for C. nobilis, (2) Crustacea for L. breviceps and O. oglinum, and (3) Mollusca for S. testudineus. The feeding activity was higher during the dry season, while the GSI was higher in the rainy season. The morphological analysis revealed a regular structure of the tissues analyzed. We highlight the presence of tubular gastric glands and strong muscular walls in the stomach (O. oglinum; L. breviceps); well-developed pyloric caecum in the intestine (O. oglinum; C. nobilis; L. breviceps); and presence of pseudo-stomach (S. testudineus). Our study confirms that the digestive tube of the examined species has morphological adequacy for carnivorous feeding habit, providing useful information on tissue structures associated to diet composition.

Diet composition and temporal changes in the trophic patterns of Plesionika narval (Crustacea-Decapoda) in the Aegean Sea (Eastern Mediterranean Sea)

The feeding habits of the Plesionika narval, narwal shrimp, from the south-eastern Aegean Sea (E. Mediterranean) were studied monthly during an annual cycle between 2014–2015. A total of 2516 specimens (1631 females and 885 males) was studied from two depth zones (A = 10–30 m, C = 150–170 m). P. narval consumed a wide variety of preys, mostly dominated by crustaceans, molluscs and polychaetes. The Shannon–Wiener diversity index (H′), did not reveal significant differences in its diet composition, either between sexes or seasons. However, the female’s diet was found to significantly differ between months and depth zones. The diet varied within sex, the average dietary dissimilarities were 18.87% among males and 12.04% among females, possibly attributed to the sexual dimorphism and/or the size differences between sexes. The low variation (<16%) in the diet composition from shallow and deep water was most possibly related to migration of females to shallower waters during spring and summer and differences in benthic preys inhabiting the two depth zones studied. The high repletion index (%RI) values observed for females in late spring and summer and for males in autumn and winter could be associated with metabolic processes, such as reproduction and moulting. The highest number of stomach emptiness in females during August in the deeper depth zone coincides with the spawning period of this species in the area under study and migration of females to shallower waters.

Biology and ecology of the accidentally introduced bleak, Alburnus alburnus (Actinopterygii: Cypriniformes: Cyprinidae), in Keddara Dam Lake, Algeria

Background. In this study, we present the results concerning the growth, reproduction, and trophic activities of bleak, Alburnus alburnus (Linnaeus, 1758), a cyprinid fish recently introduced to Algeria. We need to show that this species is adapted to local conditions. We have also characterized the biological activity of the bleak and the impact of environmental parameters on this activity. Materials and methods. The fish sampling was carried out monthly from May 2008 through February 2012 in Keddara Dam Lake, from a single sampling station located in the proximity of the dam. We studied the biometric parameters of the fish, their length&ndash;weight relation, growth parameters, the reproductive and trophic activities, as well as the physical and chemical properties of the water.&nbsp; The data collected were processed and interpreted using selected biological indices. The climatic data were obtained from the Algerian National Office of Meteorology. The statistical analysis was performed using the R program. Results. The length&ndash;weight relation of bleak represented positive allometry. The females grew less rapidly than males between 2&ndash;3 years of age. Beyond this age, females grew faster. The condition factor of females and males indicated that environmental conditions were unstable and varied between poor and good. The sex ratio was in favour of females. The reproduction activity was relatively spread over time. During the year there were many phases of sexual maturation and several spawning periods (3&ndash;4), which started from the end of January and lasted until the end of July. The last late spawning was between November and December. The sexual rest period was observed between August and September. The hepatosomatic index, in both sexes, showed no great differences. Also, the viscerosomatic index was stable. However, the repletion index was steadily increasing throughout the year. The RDA analysis&nbsp; analysis allows characterizing the biological activity of the bleak and the impact of environmental parameters. Conclusion. We have characterized the biological and ecological variability of Alburnus alburnus in its new biotope and the relation of this species to the environmental parameters. This study brings new evidence for the adaptive potential of exotic species introduced in North Africa.

Do advantages in resource exploration lead to better body condition?

The colonization of novel reservoirs tends to support opportunistic species that undergo mass proliferation after the reservoir is formed. It is common that in this process, a species will change its diet based on resource availability. This is the case in the Salto Caxias reservoir, Iguacu River, where five Astyanax species presented changes in their diets after damming. The present study aimed to evaluate possible changes in the feeding activity and condition factor of five sympatric species of Astyanax in the Salto Caxias reservoir in different areas impacted by damming. Sampling was carried out before and after damming the Salto Caxias reservoir. The fish feeding activity and nutritional status were inferred by the mean stomach repletion index and the mean condition factor, respectively. Most of the studied species showed a general decrease in feeding activity and condition factor. Both studied regions, the upstream region and the dam region, presented changes in the analyzed factors. These observations suggest that regardless of diet changes, nutritional status is negatively impacted in altered environments. The nutritional deficit occurs (i) if the diet is altered due to adaptive limitations on the use of the available resources and (ii) if the diet remains unaltered due to the scarcity of the preferred feeding resource. Such decreases might lead to reductions in the population size due to limitations on growth and reproduction until the environment feeding resources can sustain those populations.

Energy acquisition and allocation to the gonadal development of Cynoscion leiachus (Perciformes, Sciaenidae) in a tropical Brazilian bay

ABSTRACTThe process of energy acquisition and allocation to the gonadal development involves the use of reserves obtained from the food intake and/or stored in different parts of the body. Some fish species acquire and store energy prior the spawning season (capital breeders). For others species, the energy acquisition through by feeding activity continues actively throughout the spawning season (income breeders). This process of acquisition/allocation of energy to gonadal development was investigated for Cynoscion leiarchus an important fishery resource in southeastern Brazil. Monthly measurements of the gonadosomatic, hepatosomatic, condition factor and stomach repletion indices were carried out. Size at the first maturation was also assessed. Fish, mainly teleosts, were the main source of energy in the diet suggesting a carnivorous behaviour. We found evidences of use of stored body energy reserves during the spawning period, associated concomitantly with a decrease of feeding activity, suggesting a capital breeder. However, the wide spawning season, together with asynchronic oocyte development and indeterminate fecundity (typical of income breeders) suggest that the mixed-breeder strategy should be more suitable for this species. The high plasticity regarding the capital-income breeder strategy during the reproductive cycle of the genus Cynoscion is discussed.

Aspects of reproductive biology of curimba Prochilodus lacustris (Pisces, Prochilodontidae) in a tropical lake in Northeastern Brazil

This study evaluated the annual cycle of biological reproductive aspects of Prochilodus lacustris, a neotropical fish species, in Baixada Maranhense Protection Area in northeastern Brazil. Fish were collected monthly between June of 2015 and June of 2016 using gill nets. In the laboratory, 600 individuals were weighed, measured, and eviscerated to obtain biometric data and data for the microscopic and macroscopic analyses of the maturation stages of the gonads. These analyses allowed the determination of the reproductive period using biological indicators such as the gonadosomatic index and hepatosomatic index, condition factor, stomach repletion index, and spawning season. Abiotic variables were measured in situ during the samplig: temperature, pH, dissolved oxygen, and electrical conductivity. In addition, local rainfall data was also obtained. The results showed that the total body length of individuals varied from 151 to 211 mm in males, and from 142 to 239 mm in females. The sex ratio showed a predominance of females over males, and the species showed negative allometric growth. The annual variation of reproductive indicators and the frequency of individuals in advanced stages of gonadal maturation suggest that the reproductive cycle of the species occurs between November and January, with a reproductive peak in January. This reproductive peak coincides with the beginning of the region's rainy season. Although we did not do the fertility analysis, our results suggest that the species presents partitioned spawning. In conclusion, this results demonstrates that the reproduction of the investigated specie is influenced by associations between environmental variables on a seasonal scale and can be contribute to improve the understanding of the dynamics of the physiological reproductive process in lentic environments.

Effect of flood pulses on the trophic ecology of four piscivorous fishes from the eastern Amazon

This study investigated the effect of hydrological periods on the feeding activity and trophic interactions of four piscivorous fishes from the middle Xingu River, Brazil: pike-characid Boulengerella cuvieri, dogtooth characin Hydrolycus armatus, dogtooth characin Hydrolycus tatauaia and South American silver croaker Plagioscion squamosissimus. Repletion Index (IR %), Alimentary Index (IAi %) and food web properties were calculated for each species. A total of 825 specimens were collected. The IR showed changes in feeding intensity of B. cuvieri, H. armatus and H. tatauaia among hydrological periods. Flood pulse showed no influence on composition and importance of food items consumed. Trophic connections showed that connectivity ranged from 0.025 to 0.038. The highest number of trophic connections (75) occurred in the high-water period, when 51 food items were recorded and the lowest number of trophic connections (43) occurred in receding water, with 31 food items. In all food webs, over 45% of food items were consumed by only one species (ultra-peripheral items), which is common in piscivorous fishes.

Downstream effects of a large reservoir on the reproductive activity of Prochilodus hartii (Pisces: Prochilodontidae)

To analyze the effect of the Irapé reservoir on the reproduction of “curimba”, Prochilodus hartii, a migratory species, 503 specimens were collected during the reproductive period from February 2012 to January 2013. Specimens were collected from two river sections within the Jequitinhonha River Basin: Site 1 – a section of the Itacambiruçu River, a tributary of the Jequitinhonha River upstream of the Irapé reservoir; and Site 2 – a section of the Jequitinhonha River immediately downstream from the Irapé dam. Specimens (n = 270) were captured at Site 1 (160 males and 110 females), and 233 specimens at Site 2 (136 males and 97 females). The following were determined for each specimen: gonadosomatic index (GSI), hepatosomatic index (HSI), stomach repletion index (SRI), coelomic fat index (CFI) and condition factor (K). Both male and female fish were captured at all stages of gonadal maturation at Site 1, whereas only fish in the inactive and initial maturation stages were captured at Site 2. Length and mean GSI were greater (P < .05) at Site 1. Mean HSI and SRI of females was less in the advanced maturation stage. There were lesser values ​​for temperature and dissolved oxygen at Site 2 than 1. It is possible that the lesser values ​​for the physical and chemical characteristics of the water at Site 2 failed to promote advanced gonadal maturation, spawning, and spermiation of P. hartii, thus there are associations that are indicative of a negative effect of the Irapé reservoir on the reproduction of this migratory species.

FOOD AND FEEDING HABITS OF SOME FISH SPECIES IN OGUN STATE COASTAL ESTUARY, OGUN STATE, NIGERIA

The food and feeding habits of eight (8) fish species Elops lacerta, Chrysichthys auratus, Schilbe mys-tus, Sardinella maderensis, Synodontis schall, Hepsetus odoe, Tilapia zillii and Mugil cephalus in Ogun estuary, Ogun State, Nigeria were studied and estimated for six months, between February and July, 2014. A total of 470 fishes were randomly collected from the commercial fishermen during the study. Results from the stomach contents analysed using frequency of occurrence and numerical methods showed that S. mystus, E. lacerta, S. maderensis, H. odoe, S. schall, T. zillii, M. cephalus and C. auratus were predators, piscivores, herbivores, piscivores, omnivores, herbivores, herbivores and omnivores respectively while H. odoe and S.mystus partly fed on E. lacerta and T. zillii respec-tively. The Diet Breadth (D) ranged from 0.76 to 0.88 and the percentage Gut Repletion Index (GRI), a reflection of frequency of feeding, ranged between 60-100%.

Impact of abiotic factors on some biological indices of Cyprinus carpio (L., 1758) in Ghrib dam lake, (Algeria)

AbstractThis study was conducted with a sample of 733 Cyprinus carpio collected between May 2013 and February 2016 from the ecosystem lake in the Ghrib dam which is eutrophic. Cyprinus carpio in this dam is characterized by a single fractional spawning that begins in the spring and ends in the late summer. The distributions of the viscerosomatic and gonadosomatic indices decrease between the spring and summer seasons. These periods correspond to the spawning period and the biological break of this species. They progressively increase between autumn and winter when the biological activity of the species returns. The hepatosomatic index progressively decreases between the spring and the summer when the hepatic reserves are used for reproduction. The repletion index shows that the trophic activity of C. carpio is intense in the spring. The condition factor varies between 1.1 and 1.35. The evolution of the biological indices of both sexes is well stressed in well‐defined periods according to the seasons. The values are weak for males and high for females. The redundancy analysis allows the characterization of the influence of the physico‐chemical parameters of the dam water, especially the role of the nutritious elements, in the biological seasonal cycle of C. carpio.

Seasonal assessment of biological indices, bioaccumulation, and bioavailability of heavy metals in sea urchins Paracentrotus lividus from Algerian west coast, applied to environmental monitoring.

The aim of the present work was to extend our knowledge on the variability of trace metals in sea urchin tissues, focusing on seasonal fluctuations (2010 February for "winter," May for "spring," August for "summer," November for "autumn") in the three different sampling sites of Algerian west coast (Oran Harbor (S1), Ain Defla (S2), and Hadjaj (belonging to Mostaganem City S3)). For this purpose, the bioavailability (metal indices) and bioaccumulation (metal concentrations in soft tissues) of heavy metals (Zn, Cu, Pb, and Cd), the physiological characteristics (e.g., biological indices such as condition index (CI), repletion index (RI), gonad index (GI)), and the biometric parameters (diameter (D) and the height (H)) of sea urchins Paracentrotus lividus were assessed and related to seasons and sites. To investigate the metal bioavailability to sea urchins more precisely, the metal indices were used as a reliable tool in the present work, instead of the metal concentrations only. The interest to standardize metal concentrations with the weight of the urchin test is to overcome the metal burden variations in the soft tissues of urchin related to the seasonal weight changes of the soft body of animal. We evidence that the most contaminated sites were S1 and S2. Furthermore, it should be noted that the bioavailability of metals, corresponding to the values of metal indices, is also more pronounced in S1 and S2 compared to that measured in S3. Thus, a correlation is observed between seasonal metal content in urchin tissues from the three sites and the corresponding metal indices. The high metal concentrations were obtained during the period when RI and CI were highest. So, it appears that the bioaccumulation of metals in sea urchins of the three sites studied is significantly influenced by the reproductive cycle and diet, feeding activity, and physiological state of these organisms. We noticed that the sea urchins from the sites S1 and S2 were small in size. It is probable that these animals, whose internal tissues contained high concentrations of metals, have been exposed to metal pollution, which might have affected both their growth and altered their physiological capacity. This approach is very original and might be used in the monitoring of the quality of coastal waters, and the present work provided a useful data set for Mediterranean monitoring network.