The biology of the Red Sea migrant,Saurida undosquamis in the Mediterranean and comparison with the indigenous confamilial Synodus saurus (Teleostei: Synodontidae)

A study of the biology of Red Sea — Suez Canal migrant, the lizardfish Saurida undosquamis and the indigenous Synodus saurus was carried out in the Mediterranean coast of Israel. The spawning season of S. undosquamis lasts from March to December indicating a curtailment of the year-round spawning season of the source population in the Gulf of Oman. The spawning season of S. saurus is from February to August. The diameter of ripe oocytes of S. undosquamis is 500–600 μm. Females of S. undosquamis grow slightly faster than males and reach a larger size (340 mm TL versus 280 mm TL). Niche partitioning between the two lizardfishes is primarily on the basis of depth. The invador occupying deeper water. Both species are chiefly piscivorous but as a result of their depth distribution there is little diet overlap on the specific level.     

Molecular analysis of the recently described lizardfish Saurida lessepsianus (Synodontidae) from the Red Sea and the Mediterranean,with remarks on its phylogeny and genetic bottleneck effect

The opening of the Suez Canal in 1869 led to a massive influx of Red Sea species that invaded the Mediterranean; this was termed ‘Lessepsian migration'. Among these species was a species of lizardfish, identified by some authors as Saurida undosquamis and by others as S. macrolepis. Recently, the Red Sea and the Mediterranean populations were described according to external characteristics as a unique taxon, Saurida lessepsianus. Our molecular study confirms this finding and determines that all previous records of S. undosquamis and S. macrolepis in the Red Sea and the Mediterranean are misidentifications of S. lessepsianus. The Mediterranean population of S. lessepsianus exhibits a lower genetic variability than that of the Red Sea population, suggesting a bottleneck effect.     

The Saurida undosquamis group (Aulopiformes: Synodontidae), with description of a new species from southern Japan

Four lizardfishes of Saurida (family Synodontidae), S. undosquamis, S. umeyoshii sp. nov., S. macrolepis, and S. longimanus, are described. All are recognized here as the Saurida undosquamis group, characterized by having dark dots on the upper margin of the caudal fin, pectoral fin exceeding origin to pelvic fin, anterior rays of dorsal fin neither elongate nor filamentous, predorsal length greater than distance between dorsal-fin and adipose-fin origins, 46–55 pored lateral-line scales, and vomer with 0–8 teeth. Saurida undosquamis, from northern West India and West Pacific, excluding East Asia, differs from others in having lateral-line scales ridged on the caudal peduncle, conspicuously concave posterior margin of the pectoral fin, 51–55 pored lateral-line scales, and 50–53 vertebrae. Saurida umeyoshii sp. nov., from southern Japan and the East China Sea, is defined by three rows of indistinct dark blotches on, above, and below the lateral line, distribution of scale pockets with melanophores on their posterior part extending over the entire abdominal region from the lateral line in specimens over ca. 130 mm SL, lateral-line scales not ridged on caudal peduncle, 49–52 pored lateral-line scales, and 48–50 vertebrae. Saurida macrolepis, from the Indo-West Pacific, is characterized by 46–49 pored lateral-line scales and 45–48 vertebrae. Saurida longimanus, from northern West India, northwest Australia, and southern Indonesia, differs from the others in having a long pectoral fin extending past the origin of the dorsal fin. Some geographic variations are found in S. macrolepis. Saurida grandisquamis is confirmed as a junior synonym of S. undosquamis, based on examination of the type specimens. A key to species in the S. undosquamis group is included.     

Feeding ecology of the estuarine dolphin (Sotalia guianensis) on the coast of Rio Grande do Norte,Brazil

We analyzed the stomach contents of 40 estuarine dolphins, Sotalia guianensis (van Benédén 1864), beached on the coast of Rio Grande do Norte, Brazil, between February 2000 and February 2007. A total of 223 prey items were identified, including 18 species of teleosts and 5 species of cephalopods. The index of relative importance (IRI) showed that Larimus breviceps, Haemulon plumieri, Lutjanus synagris, Trichiurus lepturus, Mugil curema, and Diapterus rhombeus were the six most important species. The IRI showed that L. breviceps was the main prey for both adults and the young. H. plumieri was the most important for the males and T. lepturus for the females. Seven species of teleosts and two of cephalopods were recorded in the diet of estuarine dolphins for the first time in the country. Our results suggest that the estuarine dolphin can be a feeding specialist and that foraging activity occurs mainly in estuarine areas, where the animals can use passive listening to detect prey.     

Impacts of variability of habitat factors on species composition of ichthyoplankton and distribution of fish spawning ground in the Changjiang River estuary and its adjacent waters

During June, August and October 2006, there were three multi-disciplinary surveys carried out in the Changjiang River estuary and its adjacent waters (122°00′–125°00′E, 27°50′–34°00′N) by R/V Beidou to study the species composition and abundance of ichthyoplankton (including fish eggs, larvae and juveniles), the spatial distribution of fish spawning ground and their relationship with habitat factors. There were 29, 29 and 25 grid stations sampled in the three cruises, respectively. The ichthyoplankton samples were collected by horizontally towing with a macro-plankton net (mouth diameter 80 cm, length 270 cm, mesh size 0.50 mm) at the sea surface, and the towing speed was 3.0 n mile/h at each sampling station. The towing lasted for 10 min. After hauling for each station, habitat factors including temperature and salinity were measured by Sea Bird-25 CTD. Samples were preserved in 5% formaldehyde solution immediately after sampling for analysis in laboratory. Since the trawl speed could not be accurately evaluated due to the effects of ocean currents and wind-induced wave, the amount of ichthyoplankton was evaluated by actual number of the sampling haul in each station. Ichthyoplankton collected were divided into three categories: dominant species, important species and main species by the index of relative importance (IRI). There are 71 species (including 1200 fish eggs and 2575 fish larvae and juveniles) collected during 3 cruises and 59 species have been correctly identified to species level, which belongs to 50 genera, 37 families and 9 orders; while 5 species can only be identified to genera level, 1 species only identified to family level and 6 species identified to order level. These 59 species identified to species level and 5 species identified to genera level are divided into three ecological patterns, i.e., brackish water species, neritic water species and coastal water species. Warm water species have 34 species in those 59 species identified to species level, accounting for 57.63%, warm temperature species have 25 species, accounting for 42.37%. According to the analysis of IRI, the dominant species are Engraulis japonicus (in June and August, that is important species in October), Scomber japonicus (in August), and Johnius grypotus (in October) during the survey; important species are Cynoglossus joyneri (in June and August), Trichiurus lepturus (in June, August and October), Gonorhynchus abbreviatus (in August), Stolephorus commersonii (in October), Saurida undosquamis (in October) and Saurida elongate (in October), and main species have 12 species in June, 9 species in August and 10 species in October, respectively. The amount of fish eggs and larvae of the dominant species, important species and main species (28 species) are 97.50% and 97.13% of the total amount of fish eggs and larvae, respectively, which are the important composition of fish eggs and larvae in the Changjiang River estuary and its adjacent waters.
In June and August of 2006, if compared with that in corresponding months in 1986, there are great changes in the habitat factors especially for temperature and salinity in the investigating areas: high salinity water from off-shelf is much closer to the coastal areas which results in the dramatic increase of sea surface salinity during all three surveys. Sea surface temperature, on the other hand, decreases distinctively in June, but significantly increases in August. The run-off of the Changjiang River greatly reduced due to the long-term drought in summer 2006, which is responsible for the great changes of habitat factors in the Changjiang River estuary and its adjacent waters. The habitat of the Changjiang River estuary is greatly changed, which consequently has significant influences on the spawning, breeding and the spatial distribution of spawning ground of neritic water species, such as Sardinella zunasi, Thryssa kammalensis, Thryssa mystax, Setipinna taty and S. commersonii ect, and coastal water species, such as Ilisha elongate and Konosirus punctatus ect.     

Biochemical systematics of Trichiurus lepturus and T. japonicus (Perciformes,Trichiuridae) from Taiwan Strait

Two morphological different species of hairtails, Trichiurus lepturus and T. japonicus were compared by starch gel electrophoresis. Isozyme patterns of eight metabolic enzymes and general muscle proteins using extracts of eye, muscle, liver and heart revealed 16 loci. The polymorphic loci were sAAT-1, GPI-A, GPI-B, IDHP-1 and PGM-2 for at least one of the two species. There were no fixed allelic isozyme patterns to differentiate among them. NEI's genetic identity (I) between the two species was calculated. An I index of 0.986 suggests that the two morphologically different hairtails belong to the same species, Trichiurus lepturus.     

Genetic divergence in lizardfishes of the genusSaurida from southern Japan

Genetic divergence in four taxa of three species ofSaurida, S. undosquamis south (S) and north (N) types,S. wanieso andS. elongata caught from the East China Sea, Sea of Hyuga and Tosa Bay, was studied based on allelic frequencies at 23 genetic loci surveyed electrophoretically. Fixed allele substitution was observed at eight loci between the S and N types ofS. undosquamis and their genetic distance was 0.5582, within a range of differentiation at the species level. The S type ofS. undosquamis was found to inhabit the Sea of Hyuga and off Cape Ashizuri along the Kuroshio Current, in addition to the East China Sea. The low level of genetic variation found for this type was discussed in relation to its restricted habitat at the edge of the continental shelf. These factors, along with some morphological characters, indicate that the two types ofS. undosquamis should be recognized as distinct species.     

Genetic Variation at the Mitochondrial 16S rRNA Gene among Trichiurus lepturus (Teleostei:Trichiuridae) from Various Localities: Preliminary Evidence of a New Species from West Coast of Africa

The taxonomic classification of large head hairtail (Trichiurus lepturus) is controversial because of similar body appearance and silvery coloration. Ten samples of T. lepturus caught off the west coast of Africa and 43 samples of T. lepturus caught off the western Atlantic coast and Indo-Pacific waters were used for sequence comparison of mitochondrial DNA encoded partial 16S ribosomal RNA(16S rRNA) gene. Ten samples of T. japonicus (obtained from various parts of southern Japan) were also included in the comparative analysis. For the 509 bp sequence determined, 58 sites were variable, of which 53 were parsimony informative. Phylogenetic analyses using maximum parsimony, maximum likelihood and Bayesian algorithm with Eupleurogrammus muticus as outgroup, showed that the haplotypes of T. lepturus obtained from the West coast of Africa, Indo-Pacific and Western Atlantic coast constituted clearly distinct and well supported lineages without any sharing and overlapping between them. Previous morphological analyses and this genetic study strongly indicate that the morphotypes of T. lepturus obtained from the West African coast are genetically distinct and probably represents a separate species.     

Comparison of a rigid grid to a square‐mesh panel in size selection for commercial fishing in the Persian Gulf shrimp trawl fishery

Two bycatch reduction devices (BRDs): a juvenile and trash fish excluder device (JTED) and a square‐mesh panel (SMP), were tested in the Persian Gulf shrimp fishery from a small‐scale shrimp trawler in October–November 2012. Each device was alternatively tested by using a small‐mesh cover net to retain individuals that escaped the BRDs. Three valuable fish species—tigertooth croaker (Otolithes ruber), silver pomfret (Pampus argenteus) and silver sillago (Sillago sihama)—were selected for detailed analyses. Average escapement rates by number for commercial species in the trawl nets with either JTED or SMP were calculated as 24% and 33%, respectively. There were significant differences in escapement rates for Otolithes ruber and Sillago sihama between JTED and SMP (p < .05). In both BRDs, Pampus argenteus had the smallest escapement rate. A two‐sample Kolmogorov–Smirnov test detected a significant difference (p < .05) in the length‐frequency of Sillago sihama, and Otolithes ruber captured in the codend and cover net equipped with JTED. Selectivity curves of both BRDs indicated that for each species, the length of 50% retention probability (L50) was substantially smaller than the length at maturity (Lm), except for Otolithes ruber. From an ecological perspective, the codend equipped with SMP was superior to the codend equipped with JTED because it retained substantially fewer under‐sized fish and had the smallest selection range. It therefore seems that replacing the standard codend with a codend equipped with SMP provides the best outcome for the fishery whereby fishermen will increase their catches of larger fish while simultaneously reducing their under‐sized fish catches.     

Molecular identification and phylogenetic relationships of seven Indian Sciaenids (Pisces: Perciformes,Sciaenidae) based on 16S rRNA and cytochrome c oxidase subunit I mitochondrial genes

The partial sequences of 16S rRNA and cytochrome c oxidase subunit I (COI) mitochondrial genes were analyzed for species identification and phylogenetic relationships among the commercially important Indian sciaenids (Otolithes cuvieri, Otolithes ruber, Johnius dussumieri, Johnius elongatus, Johnieops vogleri, Otolithoides biauritus and Protonibea diacanthus). Sequence analysis of both genes revealed that the seven species fell into three distinct groups, which were genetically distant from each other and exhibited identical phylogenetic resolution. Partial sequences of both the genes provided sufficient phylogenetic information to distinguish the seven sciaenids indicating the usefulness of mtDNA-based approach in species identification.     

Growth and mortality of exploited fishes in China's coastal seas and their uses for yield‐per‐recruit analyses

Given the scarcity of information suitable for other forms of fish stock assessments, the growth, and mortality of 10 important marine exploited fishes in China's coastal seas were estimated, based on published length‐frequency data and the ELEFAN approach and software. The resulting parameters, complemented with growth curves from FishBase were then used for yield‐per‐recruit analyses. These 10 species were both traditional commercial species (Trichiurus lepturus, Larimichthys polyactis, Scomber japonicus) and less commercial interest species (Coilia nasus, Engraulis japonicus, Decapterus maruadsi, Psenopsis anomala, Coilia mystus, Setipinna tenuifilis, Harpadon nehereus). The yield‐per‐recruit analyses indicated that the fishing mortality experienced by these 10 fish species was very high, especially in view of the extremely small cod‐end mesh sizes deployed by Chinese trawlers, of about 10 mm or less (vs. 25 mm as minimum legal size). More precisely, all 10 species suffered from growth overfishing, which was very pronounced in large species. Indeed, enlarging cod‐end mesh size, by increasing mean sizes at first capture, would increase yield‐per‐recruit for all 10 fish species by a factor of up to 2.5. Obviously, such increases in mesh size would have to be in tandem with other management measures designed to ensure the sustainability of China's marine fisheries resources.     

Age,growth and reproduction of cutlassfishes Trichiurus spp. in the southern East China Sea

The cutlassfish is one of the most commercially important continental fishes in the East China Sea. However, the current classification of cutlassfishes is suboptimal and complicates fisheries management. This study investigated the growth and reproduction of three cutlassfish species in the southern East China Sea. Between August 2002 and September 2003, a total of 2717 specimens of Trichiurus japonicus, T. sp.2 (likely synonymous for T. nanhaiensis) and T. lepturus were collected monthly from Daxi, Anping, Nanfangao, Donggang and Xingang fishing ports. The von Bertalanffy growth model in preanal length (PL) resulted in PL (mm) for T. japonicus, PL(mm) for T. sp.2 and PL (mm) for T. lepturus. Their growths were significantly different between sexes for T. japonicus and T. sp.2 and among the three species. From macroscopic examination of ovaries, histological inspection of oocytes, and analyses of gonosomatic and hepatosomatic indices, T. japonicus was likely to spawn all year round, with two peaks in February–July and November–December. T. sp.2 spawned relatively later, between April and August. The length at sexual maturity of T. japonicus females was 264 mm PL or 746 mm total length. The sex ratios of T. japonicus and T. sp.2 were significantly different from 1 : 1 whereas T. lepturus showed no significant difference. The three species of trichiurids have different geographical distributions in this region.     

Genetic differences among three species of the genus Trichiurus (Perciformes: Trichiuridae) based on mitochondrial DNA analysis

The mitochondrial DNA segment encoding the 16S ribosomal RNA (16S rRNA) gene sequence (ca. 600 bp) was compared among Trichiurus sp. 2 (sensu Nakabo, 2002) (obtained from various areas of Japan), T. japonicus Temminck and Schlegel (collected from various localities within Japan), and true T. lepturus Linnaeus (caught off the Atlantic coast of the United States and Brazil) of the family Trichiuridae using 10, 10, and 15 specimens, respectively. Based on phylogenetic analysis using a neighbor-joining (NJ) algorithm, the haplotypes of Trichiurus sp. 2, T. japonicus, and T. lepturus indicated three distinct monophyletic lineages, being supported by 100% bootstrap values with no haplotypes overlapping or sharing among the lineages. Trichiurus sp. 2, T. japonicus, and T. lepturus are genetically different from each other, suggesting that they are three distinct species.     

The diet of native and invasive fish species along the eastern Mediterranean coast (Osteichthyes)

The opening of the Suez Canal in 1869 enabled the invasion of more than 100 alien fish species into the Mediterranean. The aim of the present study was to compare the diet of native and alien fish species and to identify possibly shared food resources. We examined the diet composition of 13 of the most abundant fish species (6 alien, 7 native) on shallow soft bottom off southern Israel. All 13 species are omnivorous/carnivorous. The native fish exhibited a wider diversity of food types than the aliens. Alien fish prey upon and are preyed by native species as well as by other alien fish. A high level of diet overlap was found among some species, the aliens Saurida lessepsianus and Scomberomorus commerson overlapped with the native Synodus saurus; and the alien Nemipterus randalli with the native species Pagrus caeruleostictus, Lithognathus mormyrus and Pagellus erythrinus. The identified diet overlap is discussed, and the possibility of competitive interactions between these species is considered.     

Winter spatial distribution of fish larvae assemblages relative to the hydrography of the waters surrounding Taiwan

The aim of this study was to investigate the species composition and distribution of fish larvae in relation to hydrographic conditions in the waters surrounding Taiwan Island (TI) in February 2003. In total, 242 kinds of fish larvae belonging to 127 genera and 75 families were recognized. Among these, 109 taxa were identified to the family or genus level, others to the species level. The 12 predominant types, which constituted 71% of the total fish larvae, were Engraulis japonica, Scomber sp., Diaphus spp., Benthosema pterotum, Carangoides ferdau, Embolichthys mitsukurii, Maurolicus sp., unidentified Myctophidae, Gonostoma gracile, Trichiurus lepturus, unidentified Gobiidae, and Myctophum asperum. The distribution of fish larvae showed a clear association with water masses around TI, with higher abundances and lower species richness northwest of TI where the China Coastal Current prevails, and lower abundances and higher species diversity east of TI where the Kuroshio Current dominates. Cluster analysis distinguished three station groups and four species groups, and the distribution patterns of fish larvae also corresponded to hydrographic conditions. The total abundances of fish larvae and eight of the 12 predominant taxa showed significant and positive correlations with zooplankton abundance, which suggests that food source might be a key factor determining the abundance and distribution of fish larvae during the winter.     

The complete mitochondrial genome sequence of the cutlassfish Trichiurus japonicus (Perciformes: Trichiuridae): Genome characterization and phylogenetic considerations

Mitochondrial genome sequence and structure analysis has become a powerful tool for studying molecular evolution and phylogenetic relationships. To understand the systematic status of Trichiurus japonicus in suborder Scombroidei, we determined the complete mitochondrial genome (mitogenome) sequence using the long-polymerase chain reaction (long-PCR) and shotgun sequencing method. The entire mitogenome is 16,796 bp in length and has three unusual features, including (1) the absence of tRNA^Pro gene, (2) the possibly nonfunctional light-strand replication origin (O_L) showing a shorter loop in secondary structure and no conserved motif (5'-GCCGG-3'), (3) two sets of the tandem repeats at the 5' and 3' ends of the control region. The three features seem common for Trichiurus mitogenomes, as we have confirmed them in other three T. japonicus individuals and in T. nanhaiensis. Phylogenetic analysis does not support the monophyly of Trichiuridae, which is against the morphological result. T. japonicus is most closely related to those species of family Scombridae; they in turn have a sister relationship with Perciformes members including suborders Acanthuroidei, Caproidei, Notothenioidei, Zoarcoidei, Trachinoidei, and some species of Labroidei, based on the current dataset of complete mitogenome. T. japonicus together with T. brevis, T. lepturus and Aphanopus carbo form a clade distinct from Lepidopus caudatus in terms of the complete Cyt b sequences. T. japonicus mitogenome, as the first discovered complete mitogenome of Trichiuridae, should provide important information on both genomics and phylogenetics of Trichiuridae.     

Multiplex genotyping based on the melting temperature of a single locked nucleic acid probe

Locked nucleic acid (LNA) is a modified RNA nucleotide that can be incorporated at specific positions to generate probes with the desired length, melting temperature (T_M), and specificity. Here, we describe a method of multiplex genotyping based on dramatic shifts in the T_M of a single dual-labeled LNA probe. Using this method, two varieties of the hairtail fish Trichiurus lepturus can be distinguished from each other, as well as from Trichiurus japonicus, based on a 1- to 2-bp difference in a fragment of mitochondrial cytochrome oxidase subunit 1. The shift in T_M was 15 °C for a 1-bp mismatch and 27 °C for a 2-bp mismatch, indicating remarkable specificity. We anticipate that the method will be widely useful in applications such as species identification that require accurate, multiplex, and efficient detection of DNA polymorphisms.     

The first record of two demersal calanoid copepods,Pseudodiaptomus poplesia and P. nihonkaiensis in Korea,with remarks on morphology of the genital area

The demersal calanoid copepods Pseudodiaptomus nihonkaiensis Hirakawa, 1983 and P. poplesia (Shen, 1955) are redescribed from Korean waters. Using scanning electron microscopy, we examine the morphology of the female genital systems of four species of Pseudodiaptomus (P. inopinus, P. marinus, P. nihonkaiensis and P. poplesia), revealing interspecific differences. The zoogeography of these four species is discussed.     

The mysid-feeding guild of demersal fishes in the brackish zone of the Westerschelde estuary

The demersal fish fauna of the mesohaline zone of the Westerschelde estuary (south-west Netherlands) was sampled intensively in the period 1990–1992. Almost 500 beam trawl samples were taken in both subtidal (330 samples) and intertidal (144 samples) habitats. These yielded 44 fish species, mostly as juveniles. The area functioned as a nursery for several demersal fish species, and harboured large populations of hyperbenthic mysids. Three gobies, three flatfish, one clupeoid and one gadoid dominated the fish fauna, while three mysid species were important components of the holohyperbenthos. From c. 1500 stomach contents of 25 fish species, 44 prey species were identified, the most abundant of which were also common in the hyperbenthal. The demersal fish community consisted of a group that foraged subtidally on fast-moving epi-and hyperbenthic prey (for example gadoids, gobies and clupeoids) and a group that foraged on slow-moving or sessile endobenthic organisms, mainly in intertidal areas (for example most flatfish species). Mysidacea occurred in >50% stomachs analysed and were taken as prey by 19 of the 25 fish species. Mysids were most important in the diets of Pomatoschistus minutus, P. lozanoi, Trisopterus luscus and Merlangius merlangus, and were present in appreciable numbers in Pleuronectes flesus, Trigla lucerna, Clupea harengus and Pleuronectes platessa. These species fed mainly on the brackish water endemic Neomysis integer. Mesopodopsis slabberi (present in 35% of the gobiid stomachs) and Gastrosaccus spinifer(present in 25% of the gadoid stomachs) were of secondary importance. P. minutus and T. luscus showed a diet shift from calanoids (Eurytemora aYnis and Temora longicornis) to mysids at L_S of 30 and 50 mm, respectively. Only 1% of the standing stocks of the N. integer and M. slabberi populations was removed by the local demersal fish community, so top–down control of mysid populations in estuaries seems unlikely.