Spawning frequency, fecundity, egg weight and spawning type of silver pomfret, Pampus argenteus (Euphrasen) (Stromateidae), in Kuwait waters

Silver pomfret, Pampus argenteus, were collected by fishing with drift gillnets on one spawning ground in Kuwait waters during 1998–2000. Fish size frequency, sex ratio, maturation cycle, spawning frequency, fecundity and egg weight were assessed. The length–weight relationship differed between sexes whereby females were significantly bigger than males. Spawning started in mid‐May and continued until early October. During this time the water temperature ranged from 26.0 to 32.8°C, salinity was ? 39.0‰ and water depth ranged between 5 and 12 m. Large females spawned earlier than young spawners and the overall percentage of males during the spawning period was 70.3%. Spawning occurred after 13.00 h, with peak spawning between 15.00 and 18.00 hours during outgoing tide. Mean daily spawning frequency amounted to 63.2%. Spawning activity was found to be associated with the lunar cycle and spawnings were concentrated during the first and third quarters of the moon period, indicating a semilunar reproduction cycle. It was concluded that a female would spawn at least six times during the season. No change was observed in relative fecundity during the peak spawning season (June–August). Average relative batch fecundity was 176.3 eggs g^?1 somatic weight (SW), corresponding to a relative total fecundity of 1058 eggs g^?1 SW, which is 1.5 times higher than estimates obtained from counting the standing stock of oocytes. Bigger fish produced heavier eggs and the egg weight decreased as the spawning season progressed. Based on gonadal cycles, oocyte size frequency distribution and total fecundity, we concluded that silver pomfret is a multiple batch spawner with indeterminate fecundity.     

Molecular identification of Pampus fishes (Perciformes, Stromateidae)

Concerning the nomenclature, most problems arise from the great confusion due to the morphological similarities in Pampus. Twenty-five individuals in Pampus were sampled from different localities about 2,000 km apart along the coast of China covering the Yellow Sea, the East China Sea and the South China Sea. The sequences of cytochrome c oxidase I (COI) and 16S rRNA (16S) genes of the mitogenomes were determined. Combined with the morphological characteristics, five Pampus species, P. minor, P. punctatissimus, P. chinensis, P. cinereus and Pampus sp., were identified. The genetic distance of intraspecies ranged from 0.000 to 0.004, while it varied from 0.012 to 0.133 for interspecies based on the 16S sequences. For COI sequence data analysis, the genetic distance of intraspecies ranged from 0.000 to 0.005, while it varied from 0.057 to 0.162 for interspecies. Phylogenetic trees showed that all Pampus fishes reciprocally constituted a monophyletic group with strong support. The sister-group relationships between P. minor and Pampus sp. and between P. chinensis and P. punctatissimus were revealed respectively. In the current GenBank data, P. minor is considered P. cinereus or P. argenteus by mistake. For the lack of a P. echinogaster specimen, we cannot decide on the name of Pampus sp. as P. argenteus or P. echinogaster.     

Reproductive biology of the silver pomfret, Pampus argenteus (Euphrasen), in Kuwait waters

The reproductive activities of the silver pomfret, Pampus argenteus (Euphrasen), in Kuwait waters were investigated from March 1996 to February 1998. Observations on the seasonal distribution of maturity stages and variations in seasonal fluctuations in the gonadosomatic index (GSI) confirmed recent findings that the spawning period begins in May. The species has a prolonged spawning period in the females extending from May to August, whereas the males mature in April and ripe specimens were encountered in monthly samples until September. The recruitment pattern confirmed the one breeding season. There are two spawning peaks, the first in May and the second in August. Variations in GSI relative to fish length indicated that females and males are most fecund at about 24.5–26.4 cm and 20.5–22.4 cm length classes, respectively. The males mature earlier than females, at a minimum size of 12.5–14.4 cm, while the females mature at 20.5–22.4 cm. The oocyte diameter‐frequency distribution suggests a serial rhythm of spawning. Fecundity ranged from 28 965 to 455 661 and correlated positively with: (a) standard length (P < 0.006); (b) ovary weight (P < 0.001); and (c) body weight (P < 0.001), and negatively with egg size (P < 0.003).     

Whole body and egg amino acid composition of silver pomfret,Pampus argenteus (Euphrasen, 1788) and prediction of dietary requirements for essential amino acids

Whole body and egg essential amino acid (EAA) composition of silver pomfret, Pampus argenteus, was determined to estimate their dietary requirements using A/E ratios as an indicator. Ten adult fish (sex ratio 1 : 1) were sampled each month from Kuwaiti waters for a 1‐year period (November 2007 to October 2008). There was no significant difference (P > 0.05) between the whole body amino acid (AA) composition of males and females except for glutamic acid and serine. There were no significant differences (P > 0.05) between the contents of leucine, methionine, phenylalanine and threonine in whole body and eggs. However, arginine, isoleucine and valine contents in eggs were significantly higher than those of whole body, while lysine and histidine in whole body was significantly higher than that of eggs. Among non‐essential AAs, cystine, tyrosine, alanine, and serine content in eggs were significantly (P < 0.05) higher than those in whole body. A high correlation between the whole body A/E ratios of silver pomfret with the A/E ratios for P. argenteus (r² = 0.79), P. punctatissimus (r² = 0.90), sea bream (r² = 0.81), sea bass (r² = 0.69) and Japanese flounder (r² = 0.95) was observed. Based on a lysine requirement value of 4.5 g per 100 g protein for Asian sea bass, the EAA requirement values of histidine, leucine, lysine and threonine for silver pomfret estimated using whole body EAA composition was slightly higher than those of eggs values. On the other hand, arginine, isoleucine, Met + Cys, Phe + Tyr, and valine values estimated using egg composition in silver pomfret were slightly higher than those estimated by whole body composition. However, a higher correlation was observed with the whole body EAA composition and estimated EAA requirement values (r² = 0.81) compared to that with eggs (r² = 0.72). Until dose‐response experiments are carried out to determine the EAA requirements precisely, the estimated EAA values using whole body EAA as proposed in this study could be used when formulating diets for silver pomfret.     

Microgemma vivaresi n. sp. (Microsporidia, Tetramicridae), infecting liver and skeletal muscle of sea scorpions, Taurulus bubalis (Euphrasen 1786) (Osteichthyes, Cottidae), an inshore, littoral fish

The ultrastructure of a new microsporidian species Microgemma vivaresi n. sp. causing liver cell xenoma formation in sea scorpions, Taurulus bubalis, is described. Stages of merogony, sporogony, and sporogenesis are mixed in the central cytoplasm of developing xenomas. All stages have unpaired nuclei. Uninucleate and multinucleate meronts lie within vacuoles formed from host endoplasmic reticulum and divide by binary or multiple fission. Sporonts, no longer in vacuoles, deposit plaques of surface coat on the plasma membrane that cause the surface to pucker. Division occurs at the puckered stage into sporoblast mother cells, on which plaques join up to complete the surface coat. A final binary fission gives rise to sporoblasts. A dense globule, thought to be involved in polar tube synthesis, is gradually dispersed during spore maturation. Spores are broadly ovoid, have a large posterior vacuole, and measure 3.6 microm x 2.1 microm (fresh). The polar tube has a short wide anterior section that constricts abruptly, then runs posteriad to coil about eight times around the posterior vacuole with granular contents. The polaroplast has up to 40 membranes arranged in pairs mostly attached to the wide region of the polar tube and directed posteriorly around a cytoplasm of a coarsely granular appearance. The species is placed alongside the type species Microgemma hepaticusRalphs and Matthews 1986 within the family Tetramicridae, which is transferred from the class Dihaplophasea to the class Haplophasea, as there is no evidence for the occurrence of a diplokaryotic phase.     

The new family Caucasichthyidae (Pisces,Perciformes) from the Eocene of the North Caucasus

Caucasichthys kumaensis gen. et sp. nov., a representative of a new monotypic perciform family Caucasichthyidae, from the Middle Eocene (Bartonian, Kuma Horizon) of the North Caucasus (Gorny Luch locality) is described. The new family is characterized by elongated body, strong preopercular spine in adults, absence of supraneurals, large pelvic fins, long caudal peduncle, and anal fin longer at the base than soft dorsal fin. Scales vary from cycloid to spinoid on different parts of the body. Caucasichthys shares a number of apomorphic features with members of certain percoid families, most notably the Priacanthidae. However, because of its unique combination of features, the new family cannot be properly placed within any existing perciform suborder and it is placed incertae sedis among the Perciformes.     

Age and growth of Atlantic bluefin tuna, Thunnus thynnus (Osteichthyes: Thunnidae), in the Mediterranean Sea

The objective of the study was to describe the biometry of Mediterranean bluefin tuna, Thunnus thynnus, the biology of which is not yet well understood. A total of 504 specimens was collected from 1998 to 2005 in the central part of the Mediterranean basin. They were sexed and measured; fork lengths (FL) ranged from 51.0 to 255.0 cm while body weights (W) ranged from 2.6 to 247.0 kg. The first spiniform ray (spine) of the first dorsal fin was removed and cross‐sectioned near the condyle base in order to count annuli for age estimation. The regression coefficient (b) of the female FL–W relationship was significantly higher than that of the male, and both sexes displayed a negatively allometric growth (b < 3); male regression equation: ln W = ?2.942 + 2.730 ln FL; female regression equation: ln W = ?3.660 + 2.878 ln FL. Based on counts of the translucent zones in the sections of the first ray of the first dorsal fin, estimated ages ranged from 1 to 15 years for males and 1 to 14 years for females. The correlation between the spine ray (R) and FL fit the allometric model best; the R–FL regression equations of the two sexes did not differ significantly and the overall equation was: ln FL = 3.721 + 0.851 ln R. Due to the R–FL allometric correlation, estimates of fork lengths at previous ages, FL_i, were back‐calculated with a body proportional hypothesis. Von Bertalanffy growth equations were derived from both observed and back‐calculated FLs‐at‐age, which did not differ significantly. Moreover, no significant difference was found between the growth equations of the two sexes; the overall equation was FL_t = 373.08 [1?e^{?0.07(t + 1.76)}]. Weight‐at‐age values were derived from the von Bertalanffy predicted FLs‐at‐age by the FL–W correlation equations for males and females. The paper represents the first comprehensive study on the biometry, including age and growth, of bluefin tuna captured in the Mediterranean Sea.     

Age estimation and specific growth pattern of boxlip mullet,Oedalechilus labeo (Cuvier, 1829) (Osteichthyes,Mugilidae), in the eastern Adriatic Sea

The main objective of this study was to investigate boxlip mullet, Oedalechilus labeo (Cuvier, 1829), a species that lives in open, oligotrophic and stenohaline waters, exhibits slower growth rates and has a longer life span than other mugilids. A total of 1662 specimens ranging from 2.2 to 24.4 cm TL were obtained by beach seine in the eastern Adriatic Sea. The overall sex ratio was unbalanced in favour of females (1.0 : 1.3) and differed statistically from the expected 1 : 1. The reproductive season extended through summer and autumn. All specimens above 15 cm TL were sexually mature. Length‐weight relationship for males was TW (g) = 0.010 × TL (cm)^2.975 and TW (g) = 0.009 × TL (cm)^3.014 for females. The age study comprised 150 (38.5%) males, 192 (49.4%) females, and 47 (12.1%) immature O. labeo, for a total of 389 individuals. Age of the fish was determined by scale readings, with the maximum age of 10⁺ observed for both sexes. A predominance of age classes 1⁺ and 2⁺ (71.0%) in the total catch was noted. Parameters of the von Bertalanffy growth equation for combined samples were: L_∞ = 25.93 cm, k = 0.192 year^?1 and t₀ = ?1.427 year. The growth parameters showed that males grew at a slightly lower rate than females. The size and age frequency distributions of both sexes were not significantly different. When compared to other mugilids, O. labeo reaches the lowest maximum body length and has a relatively slower growth and a longer life span.     

Mass occurrence of an introduced crustacean (Caprella cf. mutica) in the south-eastern North Sea

The caprellid amphipod Caprella mutica is indigenous to coastal waters of north-east Asia and was first recorded in European waters in 1995. We now detected mass occurrences of > 3000 individuals per m² in harbours of the two islands of Sylt and Helgoland in the German Bight, North Sea. Currently, Caprella mutica seems to be restricted to artificial hard substrata but we expect it to become a new species in natural hard bottom assemblages of that region as well.     

Impalement of marine turtles (Reptitia,Chelonia: Cheloniidae and Dermochelyidae) by billfishes (Osteichthyes,Perciformes: Istiophoridae and Xiphiidae)

Synopsis Billfishes have long been known to impale a great variety of objects, but there are only two brief, obscure records of marine turtles being speared. Details are presented on these two, as well as on two other confirmed records; data from two additional unconfirmed records are also presented. In total, three species of marine turtles are known to have been impaled by three species of billfishes; a fourth species of fish and a fourth species turtle are listed in an unconfirmed case. Records come from the eastern and western Pacific as well as the eastern Atlantic. Of the four confirmed cases, the turtles survived in two, and apparently died as an effect of the spearing in the other two. In three confirmed cases only the impaled rostrum was encountered, and in one confirmed case the entire fish was found, with its rostrum piercing the turtle. There is no obvious advantage — or clear disadvantage — involved in impaling turtles. It is argued that these attacks are accidental, and the result of attempts made by the billfish to capture prey that are near the turtle. These spearings indicate that the chelonians serve as shelters for prey animals on the high seas, and thus, are further evidence of the pelagic existence of marine turtles. The impalings are evidence of a singular ecological role of the turtles — as live fish aggregation devices.