Age and growth of Lessepsian rabbitfish from the eastern Mediterranean

Rabbitfish are currently an important component of the eastern Mediterranean inshore fishery. This study estimates age and calculates growth of Siganus rivulatus and S. luridus from the Lebanese coastal waters based on otolith analysis and compares results with available data from different geographical locations. Annual periodicity of alternating zones was confirmed for S. rivulatus, in which one opaque and one translucent zone were observed to deposit each year, but not for S. luridus. Both species appear to have a maximum lifespan of 6 years. The von Bertalanffy growth functions were L_t = 318.9(1 ? e^{?0.225(t+1.307)}) for S. rivulatus and L_t = 274.9(1 ? e^{?0.330(t+1.039)}) for S. luridus and length–weight relationships were estimated as for S. rivulatus and for S. luridus. The rabbitfish catches of the Lebanese fishery consist mainly of individuals which have not reached their first maturity. Rabbitfish from the eastern Mediterranean coastal waters appear to grow rapidly most of the year and are thus able to maintain relatively important population size despite intensive fishing pressure.     

Diet composition of the Lessepsian bluespotted cornetfish Fistularia commersonii in the eastern Mediterranean

Adaptability is an important factor in defining success or failure of an introduced species. The bluespotted cornetfish, Fistularia commersonii , invaded the Mediterranean from the Red Sea and spread quickly, displaying an explosive growth pattern in the eastern and central Mediterranean. Stomach contents of the Lessepsian piscivore were studied from off the Lebanese coast in order to describe aspects of its feeding ecology in the new environment. Cornetfish of different sizes (25–112 cm L_t) and from various habitats and depths (1–40 m) were sampled over an 18-month period (May 2003 to November 2004). Only 29% of the individuals contained identifiable prey items. The diet of the invasive cornetfish comprised a large variety of prey (41 taxa), Spicara smaris and Boops boops being the most important. Comparisons among prey habitats showed that the invasive cornetfish fed preferably on schooling species living in the water column. A large diversity of prey species characterized autumn and winter seasons while S. smaris and B. boops dominated in the spring and summer. Diet did not vary significantly with predator size except for S. smaris , which was a more important prey to middle size-classes cornetfish. The invasion of F. commersonii might have an important effect on structure and population dynamics of native communities, however it seems premature to predict the potential impact on eastern Mediterranean ecosystems or fisheries.     

Westward range expansion of the Lessepsian migrant Fistularia commersonii (Fistulariidae) in the Mediterranean Sea, with notes on its parasites

One adult female bluespotted cornetfish Fistularia commersonii was captured near the coast of Arbatax (Sardinia, Italy) in late October 2005. Macroscopic and microscopic analysis of the gonad revealed a postspawning ovary. Several body parts of the damselfish Chromis chromis were found in its stomach contents. Different developmental stages of 58 metazoan parasites belonging to Arthropoda, Nematoda and Platyhelminthes were detected in its mouth and digestive tract. The lepocreadiid Allolepidapedon fistulariae was reported for the first time from the Mediterranean and, with the exception of this species, all the parasites found were reported for the first time in this host. This new record of F. commersonii may confirm the rapid range expansion of this Lessepsian migrant in the western Mediterranean Sea, as well as the presence of its endoparasite A. fistulariae .     

Feeding habits of anglerfish,Lophius budegassa (Spinola, 1807) in the Adriatic Sea,north‐eastern Mediterranean

Stomach contents of 283 anglerfish (Lophius budegassa), collected in the Adriatic Sea (north‐eastern Mediterranean) from experimental trawl surveys in 2005 and 2006, were examined to assess their diet as influenced by fish size, sex and water depth. Changes in food quantities in the stomach were observed, the percentage of empty stomachs decreasing with increasing body size and depth. No differences were found between male and female diets. The anglerfish is essentially an ‘opportunistic feeder’ that consumes mainly fishes, crustaceans and molluscs. Fishes were the primary food consumed by all size classes; the favourite prey was Merluccius merluccius (TL >150 mm for medium and large anglerfish) and Gaidropsarus biscayensis (TL <150 mm for smaller anglerfish). However, the proportion of fish species and molluscs changed with the body size of the anglerfish. The trophic level of L. budegassa estimated in the study area reached a mean value of 4.38, confirming that the species was a carnivore with a preference for large decapodes, cephalopods and fish.     

Feeding habits and trophic levels of Mediterranean fish

The estimation of fractional trophic levels(TROPHs) is essential for the management offisheries resources as well as for quantifyingthe ecosystem effects of fishing. We gatheredall available information concerning thefeeding habits of 332 fish stocks, belonging to146 species, 59 families and 21 orders,throughout the Mediterranean Sea, and estimatedtheir TROPH values. The latter ranged from 2.0to 4.5 and the following functional trophicgroups were identified: (a) pure herbivores (TROPH = 2.0–2.1, mean = 2.02, SD = 0.03),which were very rare and represented by Siganus luridus, Siganus rivulatus andSarpa salpa, all of which feed on red,brown, green and blue-green algae; (b)omnivores with a preference for vegetablematerial (2.1 < TROPH < 2.9, mean = 2.5,SD = 0.12), but feeding on other prey, such assponges, hydrozoans, anthozoans, polychaetes,ostracods, isopods, amphipods and copepods. This type of omnivore was very rare among thecases reviewed; (c) omnivores with a preferencefor animal material (2.9 < TROPH < 3.7,mean = 3.4, SD = 0.19) feeding on a wide variety ofprey (e.g., algae, foraminifera, brachyurans,balanoids, ascidians, amphipods,appendicularians, annelids, isopods,gastropods, cnidarians, ophiurids, polychaetes,cladocerans, mysids, euphausids, fish larvae,cephalopods). They were the most numerous andwere mainly represented by species of thefamilies Blenniidae, Bothidae, Centracanthidae,Gobiidae, Labridae, Lotidae, Macrouridae,Mullidae, Ophidiidae, Soleidae, Triglidaeand Engraulidae; and (d) carnivores witha preference for large decapods, cephalopodsand fish (3.7 < TROPH < 4.5). They werethe next most abundant group among the casesreviewed. They were mainly represented byspecies of the families Dalatiidae, Lophiidae,Scombridae, Scyliorhinidae, Synodontidae,Torpedinidae, Merlucciidae, Xiphiidae andZeidae. This group was divided into twosubgroups: one exhibiting a preference fordecapods and fish (3.7 < TROPH < 4.0,mean = 3.85, SD = 0.09) and another one exhibitinga preference for fish and cephalopods (4.0 相似文献   

Feeding habits and trophic levels of Mediterranean fish

Reviews in Fish Biology and Fisheries - The estimation of fractional trophic levels(TROPHs) is essential for the management offisheries resources as well as for quantifyingthe ecosystem effects of...     

Reproductive features of the non-native Siganus luridus (Teleostei, Siganidae) during early colonization at Linosa Island (Sicily Strait, Mediterranean Sea)

In July 2003, the finding of a newly settled population of Siganus luridus at Linosa Island (Sicily Strait, Mediterranean Sea) gave us the unusual opportunity to examine the reproductive condition of a Lessepsian migrant during early phases of colonization. Aspects of gonad morphology, fecundity, atresia and oocyte dynamics were investigated by using 43 pioneer specimens collected in concomitance with their first record in the Pelagie Islands. Ovarian development was consistent with the group‐synchronous type, and testicular organization was of the unrestricted spermatogonial testis type, with cystic spermatogenesis. Both males and females had reached final stages of gonad maturation. The rates of follicular atresia were moderate: out of 17 adult females, 10 individuals did not present atretic oocytes; six exhibited <15.1% of secondary growth phase (SGP) oocytes in α‐atresia, while one female presented 45.7% of SGP in α‐atresia. Fecundity estimates did not diverge from what was observed in a reference population along the Lebanese coast. Absolute fecundity ranged from 115 739 to 740 433 oocytes per female (16.5–24.5 cm L_T). Relative fecundity ranged from 1239 to 3162 oocytes g⁻¹, with a mean of 1885 ± 868 oocytes g⁻¹. Our observations indicated that these early settled siganids are reproductively active at Linosa and suggested the forthcoming of self‐maintaining populations across the central Mediterranean area.     

Age and growth of the Randall’s threadfin bream Nemipterus randalli (Russell, 1986), a recent Lessepsian migrant in Iskenderun Bay,northeastern Mediterranean

Randall’s threadfin bream, Nemipterus randalli, first recorded in Iskenderun Bay in Turkey in 2008, seems to have increased in the region. The species, widespread in the western Indian Ocean and with a rapid expansion, appears to have migrated to the bay via the Red Sea. Although its presence in the region has been published, there has been little or no information as to age and growth parameters of this Lessepsian migrant in its new habitat. The present study aims to determine the basic age and growth parameters of the species colonized in the region. A total of 379 collected individuals were studied from November 2007 to October 2008. Total specimen lengths ranged from 4.80 to 21.50 cm, and weights from 1.10 to 138.36 g. Maximum age was 3 years for both sexes. The length–weight relationship was described as W = 0.0011 × L^3.061 (r² = 0.982). The von Bertalanffy growth parameters were: L_∞ = 34.96 cm; K = 0.214 year^?1; t₀ = ?1.244 year for the entire population. These data were compared with results from studies made in other geographic areas.     

Genomic signatures of rapid adaptive evolution in the bluespotted cornetfish,a Mediterranean Lessepsian invader

Biological invasions are increasingly creating ecological and economical problems both on land and in aquatic environments. For over a century, the Mediterranean Sea has steadily been invaded by Indian Ocean/Red Sea species (called Lessepsian invaders) via the Suez Canal, with a current estimate of ~450 species. The bluespotted cornetfish, Fistularia commersonii, considered a ‘Lessepsian sprinter’, entered the Mediterranean in 2000 and by 2007 had spread through the entire basin from Israel to Spain. The situation is unique and interesting both because of its unprecedented rapidity and by the fact that it took this species c. 130 years to immigrate into the Mediterranean. Using genome scans, with restriction site‐associated DNA (RAD) sequencing, we evaluated neutral and selected genomic regions for Mediterranean vs. Red Sea cornetfish individuals. We found that few fixed neutral changes were detectable among populations. However, almost half of the genes associated with the 47 outlier loci (potentially under selection) were related to disease resistance and osmoregulation. Due to the short time elapsed from the beginning of the invasion to our sampling, we interpret these changes as signatures of rapid adaptation that may be explained by several mechanisms including preadaptation and strong local selection. Such genomic regions are therefore good candidates to further study their role in invasion success.     

Genetic bottlenecks and successful biological invasions: the case of a recent Lessepsian migrant

Our current understanding of the mechanisms that lead to successful biological invasions is limited. Although adaptations play a central role in biological invasions, genetic studies have so far failed to produce a unified theory. The bluespotted cornetfish, a recent Red Sea invader in the Mediterranean Sea via the Suez Canal, provides an ideal case study for research in the mechanisms of invasive genetics. In this study, we show that the invading bluespotted cornetfish underwent a severe population bottleneck that reduced the genetic diversity of this immigrant to only two mitochondrial haplotypes. Although loss of genetic diversity is considered detrimental to the need to adapt to new environments, bluespotted cornetfish experienced an unprecedented success and rapid spread across the Mediterranean.     

Feeding ecology of the shortnose greeneye Chlorophthalmus agassizi Bonaparte, 1840 (Pisces: Chlorophthalmidae) in the eastern Ionian Sea (eastern Mediterranean)

The feeding ecology of Chlorophthalmus agassizi from the North Ionian Sea was examined in specimens caught during daylight hours on a seasonal basis from December 1996 to November 1997, at depths between 250 and 800 m (92 stations, total). Chlorophthalmus agassizi showed a mixed feeding strategy, exploiting a wide range of prey including mesopelagic, benthic and endobenthic organisms. Crustaceans and fishes were dominant food items in the diet year round. Diet composition showed slight seasonal fluctuations; these variations were correlated with food availability and reproductive activity. However, ontogenetic changes in the diet were relatively clear, despite the high overlap observed between small, medium and large individuals. Larger individuals are more efficient hunters that exhibit selection of prey with good swimming capabilities; smaller individuals consume prey with low mobility. Chlorophthalmus agassizi seem to be adapted to a food‐scarce environment, as typified in the deep‐water habitats of the Ionian Sea, and exploit all available niches.     

No reduction in neutral variability of mitochondrial and nuclear genes for a Lessepsian migrant, Upeneus moluccensis

Using nuclear (introns) and mitochondrial markers, two populations of the Lessepsian fish Upeneus moluccensis sampled from its original (Red Sea) and new habitat (Mediterranean Sea) were compared. No significant genetic difference was observed hence the passage through the Suez Canal does not seem to have affected the genetic diversity at the presumably neutral loci studied.     

Feeding habits and trophic levels of bluefin tuna Thunnus thynnus of different size classes in the Mediterranean Sea

Possible changes in diet and trophic levels in relation to size of Mediterranean bluefin tuna, Thunnus thynnus, were investigated using labelled carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotopes. Samples were obtained from two locations in the southern Tyrrhenian Sea (Western Mediterranean Sea) in May and October 2004. The δ¹³C and δ¹⁵N analyses revealed at least three significant isotopic groups [small juveniles (0.7–2.2 kg), sub‐adults (15–50 kg) and adults (70 to 225 kg)]. δ¹³C was negatively dependent on weight, while δ¹⁵N was positively dependent on weight [TW = 8.2 (±0.16) + 0.03 (± 0.0) *δ¹⁵N (n = 49; r = 0.91; P < 0.001)]. Different prey contribution to the diet was highlighted for each class. The diet of juveniles comprised zooplankton, small pelagic fish and some coastal fish; sub‐adults relied on medium pelagic fish, shrimps and cephalopods, and adults relied mainly on cephalopods and larger fish. The trophic level (TL) of tunas belonging to each size class was closely correlated to weight, starting from ca 3.0 TL for Group I and reaching 4.4–4.8 TL for the giants. Bluefin tuna, from small juveniles to giants, showed a shift in feeding preferences due to different use of habitats and food items as a function of the life stage.