Early development and growth of the laboratory reared north-east Atlantic mackerel Scomber scombrus L.

The early development, growth and morphological changes of mackerel Scomber scombrus were investigated at different incubation temperatures (8, 10, 13, 15 and 18° C). Details on the early life history are illustrated with special reference to morphological transformations. Culture techniques to rear larval mackerel stages are described using laboratory cultured foods. Artificially fertilized eggs were hatched after 80·6 h at 18·4° C and 256·8 h at 8·7° C. The standard length ( L _S) of the individuals at first feeding was 4·71 ± 0·18 mm. Four mortality critical periods and cannibalistic behaviour were identified. A maximum average larval size of 37·5 ± 4·41 mm L _S was attained 30 days post-hatch (dph) at 18·4° C. Development and growth were affected significantly by temperature during both endogenous and exogenous feeding periods. Larvae grew more rapidly at high, than at low temperatures. Daily specific growth rate (in mass) ranged from 2·4% at 10·6° C to 16·9% at 18·4° C. Likewise, average growth rate (in length) ranged from 0·05 mm day⁻¹ at 8·4° C to 0·37 mm day⁻¹ at 18·4° C. The allometric relationship of L _S, with several body measurements was not affected by temperature. Comparison with larvae collected in the Bay of Biscay did not show any significant difference in the dry mass and L _S relationship; conversely, the growth rate in length differed significantly between both laboratory and field conditions. The trends observed in the laboratory are described in relation to some aspects of the year-class strength regulation.     

Development of the pectoral, pelvic, dorsal and anal fins in cultured sea bream

The pectoral fin girdle was the first element of the fins to develop in Sparus aurata. By 3·1mm L _N (notochord length) the cleithrum was ossified and the cartilaginous caracoid-scapula was present. The fin was fully developed at 11·6 mm L _S (standard length) and by 16·0 mm L _S most elements of the fin were ossified. The pelvic fins were the last pair to develop and rudiments of these were first detected at 7·9 mm L _S. The pelvic fin and girdle were completely formed and ossified at 16·0 mm L _S. The development of dorsal and anal fins began at c. 6·5–7·0 mm L _S with the formation of 10 cartilaginous dorsal proximal radials and eight cartilaginous ventral proximal radials. The three cartilaginous predorsals (supraneurals) appeared at 7·7 mm L _S and the ossification of dorsal and anal proximal and distal radials began, respectively, at 10·5 mm L _S and 11·3 mm L _S. Ossified structures in the fins were also classified according to their origin, as being either dermal or endochondral. Finally the chronology of appearance of fin structures in S. aurata was compared with that reported for other Sparidae, Engraulidae and Haemulidae.     

Ontogenic changes in the allometric scaling of the mass and length relationship in Sprattus sprattus

An analysis of mass ( M ) and standard length ( L _S) data for larval, juvenile and adult sprat ( Sprattus sprattus ; Clupeidae) revealed marked changes in the allometric scaling factor ( b in     ). For sprat <44 mm L _S, b was 5·0, whereas in larger juveniles and adults, b was c. 3·4 indicating a relatively protracted metamorphic period for this species.     

Feeding and growth of early juvenile Japanese sardines in the Pacific waters off central Japan

Larval and early juvenile growth was backcalculated for individual Japanese sardines Sardinops melanostictus using the biological intercept method based on the allometric relationship between otolith radii and fish lengths. Sardines grew at 0·81 mm day⁻¹ during the larval stage. In the early juvenile stage, they grew from 32·3 to 45·4 mm fork length ( L ) over a 20-day period (0·64mm day⁻¹). Using the observed relationship between L and wet body weight ( W ), W = 0·00942 L ^2.99, W of the sardine juveniles was calculated to increase from 306 to 832 mg during the 20-day period. The carbon (C) requirement to achieve this growth in weight was estimated to increase from 5·7 to 9·6 mg day⁻¹. Stomach contents of the sardines were composed mostly of copepods (73%) and larvaceans (25%). Wet stomach content weight ( W_s ) was expressed by a power function of the W , W_s=0·731 W ^0·658. Carbon and nitrogen constituted 41·7 ± 1·5 and 10·0 ± 0·4% of the dry W_s , respectively. Stomach C content increased from 2·0 to 3·9 mg during the 20-day period. Three to four cycles of the daily turnover of stomach contents during the 16 h of daytime, corresponding to a gastric evacuation rate of 0·2–0·3 h⁻¹ under continuous feeding, met the C requirement to achieve the backcalculated growth in early juvenile sardines. The Kuroshio frontal waters seem to provide Japanese sardine juveniles with favourable growth conditions.     

Larval development of five species of blenny (Teleostei: Blenniidae) from the western central North Atlantic, with a synopsis of blennioid family characters

Light trap collections on oil and gas platforms in the northern Gulf of Mexico off Louisiana from 1995 to 1997 contained young of tessellated blenny Hypsoblennius invemar , freckled blenny Hypsoblennius ionthas , featherduster blenny Hypleurochilus multifilis , molly miller Scartella cristata and seaweed blenny Parablennius marmoreus , which are described. Interspecific differences were: number of dorsal, anal, pelvic and caudal fin elements; number of mandibular pores; presence or absence of canine teeth, hypural 5 and pectoral fin pigment; width of gill openings; length of preopercular spines (in larvae). Size at settlement differed among some taxa, but all five species settled within a narrow size window of c . 1·5 mm standard length ( L _S). Hypsoblennius invemar , H. ionthas , H. multifilis and S. cristata settled at mean sizes between 11·3 and 12·1 mm L _S, whereas P. marmoreus settled at a mean size of 19·3 mm L _S. Sexually dimorphic differences were consistently evident by 17–18 mm L _S in all species but P. marmoreus . The two smallest blennies with external characters normally associated with sexual maturity were a 20 mm male and 21 mm female H. multifilis . Primary caudal fin rays began to bifurcate between 17·0 and 18·3 mm L _S in H. invemar , H. ionthas , H. multifilis and S. cristata . Hypleurochilus multifilis displayed the external characteristics of being sexually mature at 20–21 mm L _S. Thus, bifurcation of primary caudal fin rays was an indicator of approaching sexual maturity in H. multifilis and this may also be true in the other species studied.     

Growth rate, age and size of bonefish from the Gulf of California

Growth rates of cultured first-year bonefish Albula sp. averaged 0·32 mm day⁻¹. Maximum theoretical growth (±95% CI) was 278 (±11·2) mm L _S (sexes combined), confirming that Albula sp. from the Gulf of California grow less than other species in the' vulpes 'complex.     

Larval development of Argentine hake Merluccius hubbsi

The ontogeny of the developmental stages of the hake Merluccius hubbsi is described. Fish larvae and post-transitional juveniles were collected in the Nor-Patagonian area from 1989 to 2004. The opening of the mouth and the pigmentation of the eyes are coincident with yolk resorption, finishing the yolk-sac stage. This species presents pigmentation on the head, trunk and tail typical of gadiform larvae. Pectoral fin development is completed during the transformation stage. The post-transitional juvenile stage begins when the fin-ray complements are complete and squamation begins. The fins become fully formed in the following sequence: pelvic fins, first dorsal fin, second dorsal and anal fins together, caudal fin and pectoral fins. The caudal complex is totally developed in larvae of 22·0–23·0 mm standard lengths ( L _S) and all vertebral elements are first observed in larvae of 8·5 mm L _S. The rate of development of M. hubbsi observed in this study could be faster than the rates reported for other species of Merluccius by different authors.     

Differences in temperature conditions and somatic growth rate of larval and early juvenile spring-spawned herring from the Vistula Lagoon, Baltic Sea manifested in the otolith to fish size relationship

Larval and juvenile herring Clupea harengus collected in the Polish part of the Vistula Lagoon in May-July 1997 had hatched between 17 April and 9 June and originated from three cohorts. The spawning season began on 1 March at 3·8° C and was completed on 3 June at 12·7° C. Mortality among larvae was high in the first 2 weeks of April, probably associated with significant temperature decrease at the beginning of the spawning season. The growth of 10–48 mm L _S herring was linear, highest for larvae and juveniles from the first cohort (0·58 mm mm^-1 day^-1), slower for the second cohort (0·55 mm mm^-1 day^-1) and the slowest for the third cohort (0·45 mm mm day^-1). Temperature effects on the growth were inconclusive and potentially unfavourable feeding conditions in June might have been responsible for the relatively slow growth of third cohort larvae and juveniles.
Relationships between otolith size (perimeter, length, width, area, and weight) and fish size ( L _S) differed among the three cohorts, related mostly to the positive temperature effect on otolith growth, individuals growing in warmer water had larger otoliths. Although a negative growth rate effect was observed as well, it was less significant.     

Gape morphology of cod Gadus morhua L., haddock Melanogrammus aeglefinus (L.) and whiting Merlangius merlangus (L.) through metamorphosis from larvae to juveniles in the western Irish Sea

Variations in standard length ( L _S), gape size ( S _G) and jaw length ( L _J) were studied in larval and juvenile gadoids (cod Gadus morhua , haddock Melanogrammus aeglefinus and whiting Merlangius merlangus ) from 4 to 70 mm. The increase in S _G and L _J was not linear with respect to L _S. The relationship was best described by segmented regression lines in all three species, with an inflection point at c . 10·5 mm. The S _G and L _J increased more rapidly in relation to larval L _S for individuals smaller than this inflection point size. The rates of increase slowed significantly post-inflection, an effect more noticeable in S _G data compared to L _J data. In each case, the inflection point fell in the intermediate period of development between the larval and juvenile stages, which could be considered as metamorphosis. Published equations that have been used to predict S _G from L _J lead to the overestimation of gape. New relationships are presented, which may be used to predict S _G from measurements of either L _S or upper jaw length in cod, haddock and whiting.     

Age and growth of Anguilla anguilla in the Camargue lagoons

Age and total length ( L _T) data from a 11 year monitoring of the Anguilla anguilla eel population of the Camargue lagoons (Rhône delta, southern France) were collected for glass, yellow and silver eels. Three distinct models were calibrated to describe the growth process of undifferentiated eels, females and males, respectively. Uncertainty of parameter estimates was evaluated by bootstrapping. Females were characterized by larger asymptotic body size ( L _T) than males (580 ± 50 v . 388 ± 13 mm) and faster growth, whilst the Brody growth coefficient was larger for males than for females (means ±  s . d . 3·00 10⁻³ ± 1·68 10⁻³ v . 1·73 10⁻³ ± 0·50 10⁻³). Sexual differentiation was estimated to begin at 204 ± 38 mm mean ±  s . d ., i.e . at the end of the second year in the lagoons, well before the L _T at which macroscopic differentiation became possible ( c . 300 mm). Males probably leave the lagoon or die (due to either natural or fishing mortality) within the first 3 years, whilst females can remain up to 5 years. Sexual differentiation and maturation have a major role in shaping the L _T structure of the population. The L _T and mass ( M ) data were fitted by allometric curves     . The calibration of distinct curves for data from different years indicated that the allometric coefficient a was subject to wider interannual fluctuations than the allometric exponent b . A negative correlation linked the average L _T and the allometric exponent ( r  = −0·58, P  < 0·01).     

The reproductive ecology of the southern red tabira bitterling Acheilognathus tabira jordani in Japan

The life history, population and reproductive variables of the southern red tabira bitterling Acheilognathus tabira jordani were investigated in a lowland reach of the River Ohara in Shimane Prefecture, western Honshu, Japan. Acheilognathus t. jordani , like all other species of bitterling, lays its eggs on the gills of freshwater mussels. It was the only species of bitterling present in the study reach, and three species of bivalve mussel were available to it for spawning: Anemina arcaeformis, Anodonta lauta and Corbicula leana . Spawning by A.t. jordani was recorded between early April and early July in 2003 and began at a size of 38· 0 mm standard length ( L _S) in the 1+ age class. Ovipositor length ( L _OP) during oviposition was positively correlated with female L _S, and showed significant seasonal variation, with a mean ± s.d. L _OP of 27· 5 ± 5· 3 mm ranging from 16· 8 to 42· 0 mm during the spawning period, which was shorter than that of a previously studied A. t. tabira population. Eggs of this subspecies are relatively long and elliptic in shape, with a volume of c. 2· 4 mm³. Egg number correlated positively with female L _S and both egg shape and volume changed significantly with season. The population size of adults was estimated to be 850 individuals, and comprised age 0+ to 3+ individuals with L _S ranging from 12· 0 to 72· 2 mm. The population sex ratio was significantly female biased, with seven females: three males. Egg shape and size and L _OP during oviposition in the present A. tabira population may be the result of local adaptations to the mussel species utilized and no competition with other bitterling species for spawning sites.     

Larval Konosirus punctatus(Clupeidae) in a brackish river mouth on the Pacific coast of central Japan

Eggs of Konosirus punctatus in early developmental stages were collected from the eastern part of the mouth of Sagami Bay on the Pacific coast of central Japan. Advanced‐stage eggs and early larvae with notochord length ( L _N) of <7·5 mm were collected from the inner bay near the mouth of the Sagami River. Feeding larvae of >8·4 mm L _N were distributed in the mouth of the river, and juveniles of 24–90 mm standard length ( L _S) were collected from the lower reaches of the river between the river mouth and c . 3 km upstream of the river mouth. Hatch dates of larvae and juveniles collected in 2001 ( n  = 158) and in 2002 ( n  = 109) extended from late March to late July. The relationship between the otolith radius ( R _O) and L _N or L _S changed during the metamorphosis stage as characterized by 320 μm R _O and 22 mm L _S. Otolith growth rate, as an index of somatic growth rates in larval and early juvenile stages, was higher in cohorts that hatched later in the spawning season, i.e . from March to July. Konosirus punctatus that were spawned in the bay mouth area survived with different growth histories in the bay and lower reaches of the river, and recruited to the young‐of‐year population in the Pacific coastal waters of central Japan.     

Oreoglanis infulatus, a new species of glyptosternine catfish (Siluriformes: Sisoridae) from central Vietnam

A new species of glyptosternine catfish, Oreoglanis infulatus , is described from the Lam River drainage in central Vietnam. The new species is distinguished from all its congeners by possessing the following combination of characters: a dark band running across the anal fin, a lunate and uniformly dark caudal fin, the lower lip lacking a medial notch and with a lobulate posterior margin, maxillary barbel with a rounded tip, length of caudal peduncle 19·0–22·6 % L _S, depth of caudal peduncle 2·6–3·2 % L _S, post-adipose distance 6·8–8·0 % L _S, eye diameter 10·5–12·1 % L _H, 12 principal caudal-fin rays.     

Consumption and gut evacuation rate of laboratory‐reared spotted seatrout (Sciaenidae) larvae and juveniles

The temperature and mass dependence of maximum consumption rate was measured for larval and early juvenile spotted seatrout Cynoscion nebulosus . Maximum consumption ( C _MAX) estimates were obtained from feeding and gut evacuation experiments on larvae (3·8–19 mm standard length, L _S) at three temperatures (24, 28 and 32° C), and maximum consumption experiments on juveniles at three temperatures (20, 26 and 32° C). Feeding levels were determined for larvae fed live prey ( Brachionus plicatilis and Artemia salina ) ad libitum . The midgut and total evacuation times were estimated for fish feeding continuously and discontinuously using alternate meals of tagged and untagged live prey. Temperature and fish size had significant effects on gut evacuation and consumption. The gut evacuation time increased with increasing fish size, and decreased with increasing temperatures. Mass‐specific midgut contents increased for small larvae <0·156 mg dry mass ( M _D)( c . 4 mm L _S), and decreased for larger larvae and juveniles. Maximum consumption was modelled by fitting a polynomial function to a reduced dataset of individuals feeding at high levels. The C _MAX model predicted an initial increase in specific feeding rate from 70 to 155% M _D day⁻¹ for small larvae, before declining for larger larvae and juveniles.     

Effects of delayed first feeding on the nutritional condition and mortality of California halibut larvae

The effect of the timing of first feeding (3, 4, 5, 6, 7 and 8 days post‐hatch, dph) on laboratory‐reared California halibut Paralichthys californicus larvae was evaluated by means of morphologic, morphometric and histological criteria. Larvae began to feed exogenously at 3 dph (2·7 ± 0·01 mm standard length, L _S) at 18° C. Eye pigmentation, rather than mouth opening was the most distinctive trait of California halibut larvae at first feeding. Larval growth was significantly affected by the time of first exogenous feeding. At notochord flexion (21 dph), the L _S of larvae fed for the first time at 3 dph was significantly larger (5·1 ± 0·1 mm) than that of those fed at 4 and 5 dph (4·9 ± 0·1 mm), although the latter fish had a more uniform size distribution. The point of no return was reached at 7 dph. Survival of larvae initially fed at 3, 4 and 5 dph was similar (58·4–60%), while no larvae were able to survive when food was offered for the first time between 6 and 8 dph. Food deprivation resulted in a progressive deterioration of the larval digestive system and atrophy of skeletal muscle fibres. Significant changes in the anterior and posterior enterocyte height were detected after 2 days of food deprivation. Similarly, tail height: L _S and trunk length: L _S ratios were the most sensitive morphometric indices to detect the effect of fasting on larval condition. Present results show that a combination of morphometric and histological variables can be used to evaluate the nutritional condition of California halibut larvae.     

Effects of river flow on larval growth and survival of Japanese seaperch Lateolabrax japonicus (Pisces) in the Chikugo River estuary, upper Ariake Bay

The abundance and growth history of larval and juvenile Japanese seaperch Lateolabrax japonicus were investigated in the Chikugo River estuary, upper Ariake Bay, from 1990 to 2000. Growth during the larval period (up to 15 mm standard length, L _S, the size at recruitment into the estuary) was backcalculated using sagittal otolith microstructures by the biological intercept method. Growth rates in length declined at body sizes >14 mm L _S. High freshwater discharge through the Chikugo River was associated with high temperatures of the upper Ariake Bay where the larvae spend their planktonic life. Mean larval stage duration (days) from hatch to 15 mm ( D ₁₅) varied between 48·8 and 76·2 days and was inversely correlated with the estimated mean temperature history [mean daily temperature (° C) experienced by the larvae during the period from hatch to 15 mm, T ₁₅]. Mean abundance (number m⁻²) of larvae and juveniles was highest in years when T ₁₅, D ₁₅ and freshwater discharge were at intermediate levels. Although the abundance was not correlated with either of these variables, an exponential relationship between abundance and D ₁₅ was found when data collected during the highest river discharge years (1990, 1991 and 1998) were excluded. The increase in freshwater discharge through the Chikugo River probably had the potential to enhance or diminish Japanese seaperch recruitment in two ways: 1) it could increase recruitment probability by increasing temperature and larval growth and 2) high river flow also had the potential to decrease the probability of immigration into the river by increasing larval seaward dispersion, predation due to decreased turbidity and starvation due to decreased zooplankton prey abundance in the estuary.     

Effect of body size, temperature, and salinity on the routine metabolism of larval and juvenile spotted seatrout

Routine oxygen consumption rates of young spotted seatrout Cynoscion nebulosus (Sciaenidae) were measured over a range of temperatures (24, 28, 30 and 32° C) and salinities (5, 10, 20, 35 and 45). Larvae and juveniles, 4·1–39·5 mm standard length ( L _S), ranging several orders of magnitude in dry body mass were used to estimate the mass–metabolism relationship. Oxygen consumption (μl O₂ larva⁻¹ h⁻¹) scaled isometrically with body mass for larvae <5·8 mm L _S(phase I, slope = 1·04) and allometrically thereafter (phase II, slope = 0·78). The inflection in the mass–metabolism relationship coincided with the formation of the hypural plate and an increase in the relative tail size of larvae. Salinity did not have a significant effect on routine metabolism during phase I. Temperature and salinity significantly affected routine metabolism during phase II of the mass–metabolism relationship. The effect of salinity was temperature dependent, and was significant only at 30° C. Response surfaces describing the environmental influences on routine metabolism were developed to provide a bioenergetic basis for modelling environmental constraints on growth.     

Effects of temperature on prey consumption and growth in mass of juvenile trahira Hoplias aff. malabaricus (Bloch, 1794)

The influence of temperature on prey consumption and growth in mass of juvenile trahira Hoplias aff. malabaricus were investigated. Consumption of small-sized lambari Astyanax altiparanae (mean standard length, L _S, 5·43 cm) varied from zero to 65 over a period of 30 days. Temperatures ranged from 14 to 34° C and the size of trahiras ranged from 17·5 to 24·7 cm L _S. Prey consumption differed significantly among temperatures. Trahiras at 18° C consumed significantly less than those at 30° C. A linear multiple regression model including temperature, prey consumption and L _S explained 89·4% of the variability in growth in mass. Some caution is suggested when inferring the impact of H. aff. malabaricus piscivory on assemblage structures in systems that, despite their location in tropical regions, are subjected to seasonal thermal variations.     

Ontogenetic allometric coefficient changes: implications of diet shift and morphometric traits in Hoplias malabaricus (Bloch) (Characiforme, Erythrinidae)

This study evaluated the relationship between body size and digestive tract characteristics of the important predatory freshwater fish Hoplias malabaricus , which is widely distributed in South America. The allometric coefficients were calculated for the mass and standard length ( L _S) relationships for two different L _S groups: (1) between 20 and 100 mm (characterized as insectivores) and (2) >100 mm (characterized as piscivores). Differential growth measured from the allometric coefficient, b , between the insectivore ( b < 3) and the piscivore ( b > 3) groups was detected. Anterior intestine length and pyloric caeca zone length showed significant differences between groups. Two complementary hypotheses were developed to explain the differential growth: (1) H. malabaricus has a digestive tract adapted to a piscivorous diet, which is independent of its ontogenetic stage of development, and (2) the negative allometry observed in group 1 individuals agrees with a general behavioural strategy, allowing individuals to grow in L _S during a shorter period of time.     

Growth of young-of-the-year mackerel in the Bay of Biscay

The first growth season of young-of-the-year (0+ year) mackerel Scomber scombrus , sampled in the Bay of Biscay, was parameterized to determine growth patterns. Daily increments were identified on sagittae otoliths, for calculation of age and growth of 92 larvae and 54 juveniles over the range 3·6–215·0 mm standard length ( L _S). A Gompertz curve was fitted to the length-at-age data. At the end of the first year of growth L _S was 194·2 mm, with a maximum growth increment of c . 2 mm day⁻¹, observed 62 days after hatching. Backcalculated growth increments for mackerel juveniles, during their larval stage, were higher than those observed for sampled larvae; only 10·9% of sampled larvae were estimated to survive. Growth for north-eastern Atlantic mackerel was slower than that published for north-western Atlantic mackerel. Backcalculated hatching dates for mackerel were consistent with the typical temporal distribution of mackerel spawning in the Bay of Biscay.