Otolith microstructure reveals consequences for juvenile growth of fractional spawning in an invasive goldfish Carassius auratus (Linnaeus, 1758) population

The consequences of fractional spawning on the early‐life growth rates of invasive goldfish (Carassius auratus) from the Qinghai‐Tibet Plateau were studied using the otolith microstructure of samples collected in June 2011. The effect of the estimated hatching date on the subsequent growth of individual fish was determined by back‐calculating their number of growth days, daily growth rates and the onset of their second growth season. The number of growth days in the first growth season ranged from 93 to 186 days. Following hatching, daily growth rates increased rapidly to a maximum of 0.55 mm days^?1 before declining to 0.09 mm days^?1. The effect of the duration of the first growth season on individuals was significant (P < 0.01), with later spawned fish having faster growth rates. These later spawned fish were, however, still significantly smaller in body length at the end of the first growth season (37 ± 4 mm in late hatched fish vs 55 ± 9 mm in early hatched fish). However, the smaller, later hatched fish started growing earlier in their second growth season than all other fish (P < 0.01) and subsequently achieved larger growth increments (P < 0.01), suggesting that the larger, early‐hatched fish were investing more resources in gonadal growth than somatic growth in their second growth year. Thus, this invasive population revealed considerable plasticity in their early‐life growth rates that were associated with the hatching date, potentially having substantial effects on their development in their second year of life.     

Validation of daily otolith increments in larval and juvenile Chinese sucker, <Emphasis Type="Italic">Myxocyprinus asiaticus</Emphasis>

Otolith development was observed and the formation of daily growth increments in otoliths of Chinese sucker, Myxocyprinus asiaticus, was validated by monitoring known-age larvae and juveniles in the laboratory from 2003 to 2005. Otolith shape changed with larval and juvenile development, and there was an exponential relationship until a body length of 16 mm or so, and a linear relationship after a body length of 16 mm between otolith size and fish size. The first increment was identified in larvae 1 day after hatching. The regressed equations between daily age (D) and increment number in otoliths (N) were N = −0.64 + 0.96D in lapillus, and N = −0.31 + 0.98D in sagitta. The slopes were not significantly different than 1.0. This demonstrated that otolith increments in this species were formed daily and can be used for daily age determination.     

Growth of larval and juvenile Diaphus theta (Pisces: Myctophidae) in the transitional waters of the western North Pacific

Diaphus theta is one of the most common myctophid fish species in the subarctic and transitional waters of the North Pacific. The growth of larval and juvenile D. theta was investigated using sagittal otolith increment analysis of specimens caught in transitional waters of the western North Pacific. Samples taken over a 24-h period demonstrated that otoliths exhibited daily growth cycles, allowing accurate determination of age. Calcification of the incremental zone of otoliths took place only at night, suggesting that the formation cycle of the increment of juvenile D. theta was different from that of shallow-water fishes and would be related to their diel vertical migration. The relationships between standard length (SL) and daily growth increment (D) were expressed as linear equations: SL = 2.65 + 0.141D (r ² = 0.942) for larvae of 5.1–9.6 mm SL and SL = 3.54 + 0.129D (r ² = 0.933) for juveniles of 13.7–27.6 mm SL. The growth rates were 0.14 mm d⁻¹ in larvae and 0.13 mm d⁻¹ in juveniles; this is slow compared with tropical or subtropical mycto-phid species, in which growth occurs at about twice these rates. The larval period, including the metamorphic stage, was long compared with species at lower latitudes and was estimated to be 71 days. The slow growth rate and long period of larval stage of D. theta would be the life history pattern of high-latitudinal species adapted to a low-temperature habitat. Received: March 23, 2001 / Revised: July 5, 2001 / Accepted: July 19, 2001     

Embryo and early larval stages of the Humboldt Current krill Euphausia mucronata (Crustacea: Euphausiacea)

The Humboldt Current krill, Euphausia mucronata (Crustacea: Euphausiacea), is an endemic and keystone species in the food web of this highly productive eastern border current ecosystem. The morphology and ontogeny of E. mucronata is known from calyptopis I to the adult phase, but the embryonic and early‐life stages (nauplius and metanauplius) of this broadcast spawning species are unknown. We describe the morphology and development time of these life stages to complete the knowledge of its life cycle. Embryos were obtained from purple‐gonad gravid females collected off Dichato, central Chile, during November 2012. Eight gravid females (mean=16 mm total length) were incubated in seawater at 12°C under laboratory conditions. The average development time from single‐cell embryos to the metanauplius stage was 2.2 d and hatching occurred between 20 and 25 h. The average growth rate was 0.35 mm d^?1 from the late limb bud to the metanauplius stage (range=0.21–0.48 mm d^?1). Embryos of E. mucronata had a mean chorion diameter of 0.460 mm, embryo diameter of 0.343 mm, and perivitelline space of 0.056 mm. Our biological information reported here constitutes a baseline for future ecological studies on distribution and temporal variability of spawning activity and reproductive strategies of E. mucronata in the highly variable and productive Humboldt Current ecosystem.     

Otolith features and growth of Malawian characid Hemigrammopetersius barnardi from the southwestern coast of Lake Malawi

Macro- and microstructures of the sagitta, asteriscus, and lapillus of juveniles of Malawian characid Hemigrammopetersius barnardi were observed. The sagittae were arrowhead shaped and showed development of rostra. Increments in the sagitta were observable until the bases of the rostra but were invisible in the rostra. The asteriscus had an irregular shape with an ambiguous core and notches at the margin. The ambiguous core of the asteriscus led to difficulty in discerning the first increment. The lapilli were round and fan shaped. Increments in the lapilli were distinct from the core to the margin. The daily increment deposition was validated by alizarin complexone treatment, and the increments increased at the rate of 1 day⁻¹ after hatching. These features suggested that in this species the lapillus is most appropriate for daily increment analysis. The hatching months were estimated based on the lapillus increment counts, and the results showed that this species continuously hatched in the rainy season for 6 months from November to April. The growth trajectory indicated that H. barnardi attains a total length of 50 mm within 4 months of hatching.     

Hatching patterns and larval growth of a triplefin from central Chile inferred by otolith microstructure analysis

The subtidal rocky reefs are home to a diverse range of marine animals, including small cryptic fishes, characterised by a bipartite life cycle, with benthic adults and pelagic larval stage that lasts from several days to several months. Using the otolith microstructure analysis, this study determines the hatching and larval growth patterns of the abundant triplefin Helcogrammoides chilensis (Pisces: Tripterygiidae). Fish larvae were collected during September–October 2010 and between July 2012 and April 2013 in nearshore waters (<500 m) of central Chile. Nearshore time series of ichthyoplankton samples showed that large abundance of this species occurs during early austral spring and autumn seasons. Body lengths ranged from 3.11 to 16.57 mm (1–57 days old). Sagittal microincrement analyses estimate that during the main reproductive season, larval growth rates are slow, varying between 0.145 and 0.156 mm day^?1 at a weekly scale. Back-calculated hatch days and circular statistics indicate a major hatch pulse occurring near full moon of the lunar cycle. These results suggest that reproduction occurs coupled with the upwelling season, which reduces the probability of starvation, and hatching occurs during spring tides (full moon), which increases larval dispersion and population connectivity.     

Age and growth information available from the otoliths of the Hawaiian snapper,Pristipomoides filamentosus

The otoliths of tropical fish may provide important life history information incorporated within their structural and chemical constituents. All three otoliths (sagitta, lapillus, asteriscus) of the tropical fish Pristipomoides filamentosus were examined internally by Scanning Electron Microscope methods to observe micro-increments and externally to determine three dimensional structure. It was discovered that the sagitta contained four cores and that the plane chosen to be sectioned for micro-increment enumeration could result in errors if more than one core were transversed. The medial cross sectional plane was consequently resolved to effer the most accurate micro-increment counts. Obserations of lapilli also revealed micro-increments and subsequent counts were closely correlated to those detected in the sagittae. The visualization of increments made it feasible to assess age and evolve a growth model. In addition, sagitta weight was found to be related to growth rate and may provide a quick estimate of relative growth. Chemical analyses of otoliths for stable isotopes and Sr/Ca ratios all suggested that an individual fish inhabited warmer waters as it became older. A combination of otolith structural and chemical information can provide age and growth data which is essential to the calculation of accurate population parameters.     

Effects of warming on annual production and nutrient‐use efficiency of aquatic mosses in a high Arctic lake

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The function of the ocelloid and piston in the dinoflagellate Erythropsidinium (Gymnodiniales,Dinophyceae)

The marine dinoflagellate Erythropsidinium possesses an ocelloid, the most elaborate photoreceptor organelle known in a unicellular organism, and a piston, a fast contractile appendage unknown in any other organism. The ocelloid is able to rotate, often before the cell swims. The ocelloid contains lenses that function to concentrate light. The flagellar propulsion is atrophied, and the piston is responsible for locomotion through successive extensions and contractions. During the “locomotion mode”, the contraction is ~4 times faster than the extension. The piston attained up to 50 mm · s^?1 and the cell jumps backwards at ?4 mm · s^?1, while during the piston extension the cell moves forwards. The net speed of ~?1 mm · s^?1 is faster than other dinoflagellates. The piston usually moved in the “static mode” without significant cell swimming. This study suggests that the piston is also a tactile organelle that scans the surrounding waters for prey. Erythropsidinium feeds on copepod eggs by engulfing. The end of the piston possesses a “suction cup” able to attach the prey and place it into the posterior cavity for engulfing. The cylindrical shape of Erythropsidinium, and the anterior position of the ocelloid and nucleus, are morphological adaptations that leave space for the large vacuole. Observations are provided on morphological development during cell division. Most of the described species of Erythropsidinium apparently correspond to distinct life stages of known species, and the genus Greuetodinium (=Leucopsis) corresponds to an earlier division stage.     

Early development of marine catfishes (Ariidae): from mouth brooding to the release of juveniles in nursery habitats

The development and allometric growth patterns of the ariid catfishes Cathorops spixii and Cathorops agassizii were studied from neurula embryos to juveniles. The ontogenetic sequence revealed that prior to hatching, embryos of both species are well developed, and their axial and appendicular skeletons are well ossified. Embryos of both species grow slowly longitudinally, but positively allometric growth (growth coefficient, β₁ > 1) was observed in head width and eye diameter. It is hypothesized that these growth patterns might be related to functional priorities for the development of sensory organs, such as the inner ears (otoliths), the Weberian apparatus, eyes and nostrils, during the embryonic period. The first appearance of vertebrae and otoliths, as well as the ossification of otoliths and the Weberian apparatus, occur earlier in embryos of C. agassizii than in embryos of C. spixii. After hatching, mouth‐brooded free embryos of both species grow isometrically. Negatively allometric growth was observed in head width and eye diameter during the yolk‐sac period, which is expected given that the sensory organs are already formed. Free embryos of C. agassizii are distinguishable from those of C. spixii by their larger eyes, longer snouts, longer heads and heavier yolk sacs. The end of the yolk‐sac period is characterized by a direct change from free embryo to juvenile, without a true larval period. The juveniles of the two species can also be distinguished from each other by the larger eyes of C. agassizii compared with C. spixii, as in adult fishes.     

Otolith formation,microstructure and daily increment validation in juvenile perch Perca fluviatilis

The otoliths of laboratory‐reared larval and juvenile perch Perca fluviatilis of known age were analysed to determine the age of otolith formation and validate the formation of daily increments. There was a linear relationship between number of increments and age in days post‐hatching, although by 82 days post‐hatching daily increment counts underestimated actual age by an average of 5 days. Otolith dimensions in relation to standard length indicated allometric growth of otoliths until completion of yolk absorption, and isometric growth thereafter, up to 82 days post‐hatching.     

Vaterite Otoliths from the Opah,Lampris immaculatus,and Two Species of Sunfish,Mola mola and M. ramsayi

The cosmopolitan opah Lampris immaculatus (also known as the moonfish or mariposa) occurs commonly in New Zealand waters. The otoliths of 23 individuals were examined by light microscopy. All three of the otoliths of the endolymphatic sac of the opah have the characteristic appearance of the Stolkowski crystal form of the vaterite morph of calcium carbonate. Five randomly chosen pairs of asterici and sagittae and two lapilli otoliths were shown by X-ray diffraction to be composed of vaterite. In addition to their mineral composition, the sagitta and astericus of the opah present an unusual combination of anatomical features found in both what are generally regarded as primitive and as advanced fish. Vaterite otoliths also occur in the sunfish Mola mola and M. ramsayi, but with a different crystalline habit to that found in the opah, and in a distinctively different anatomical arrangement of the endolymphatic sac. It is argued that, based on their otolith mineralogy and morphology, the opah and the sunfish are each side of one of the biochemical and anatomical boundaries involved in the separation of the teleosts from other actinopterygian fish (sturgeons, paddle fish, gars and bowfins).     

Growth and ingestion rates of larval fish populations in the coastal waters of Israel

Clupeoid larvae were collected on eight cruises between February1984 and February 1985 in the coastal waters of Israel. Fromanalysis of daily growth increments of otoliths, growth ratesof the abundant clupeoids, Engraulis encrasicolus, Sardina pilchardusand Sardinella aurita were found to be 0.55 mm day^–1,0.67 mm day^–1 and 0.60 mm day^–1, respectively, duringthe first month after hatching. Ingestion rates were estimatedusing an equation from the literature relating ingestion andgrowth of larval fish. Ingestion calculated for populationsof fish larvae in pelagic waters ranged from 0 to >23 mgC m^–2 day^–1 with maximum rates observed in April.Annual ingestion by larval fish at a pelagic station near Haifawas calculated to be 2.2 g C m^–2 year^–1, 10–20%of annual primary production estimated from ¹⁴C uptake.     

Growth and habitat separation in eight cohorts of three species of cyprinids in a subalpine lake

Synopsis Distribution and growth of the embryos, larvae and juveniles of Rutilus rutilus (roach), Scardinius erythrophthalmus (rudd) and Leuciscus cephalus (chub) from an oligotrophic subalpine lake in Tyrol, Austria, were studied during the first three to four months after hatching. R. rutilus was the first to spawn, a single cohort hatching around May 23rd. Four cohorts of S. erythrophthalmus hatched between June 19 and August 1. Three cohorts of L. cephalus hatched between July 3 and 25. The length/weight relationship of all species changed at a length of approximately 15–16 mm. R. rutilus, hatching at the lowest temperature, also showed the lowest growth rate during early life (maximum 10.4 per cent fresh body weight day^–1). In the other two species relative growth rates up to 20% day^–1) were measured. Rudd and chub remained in the shallow littoral during the whole period of observation, whereas roach left the littoral a few weeks after hatching and migrated into deeper water. A subtle shift in vertical distribution was observed for the first cohort of rudd which moved into slightly deeper water when the second cohort made its appearance.To whom correspondence should be addressed     

Estimates on age,growth and mortality of the French angelfish Pomacanthus paru (Bloch, 1787) (Teleostei: Pomacanthidae) in the southwestern Atlantic

The aim of the present study was to determine age, growth and mortality of the French angelfish Pomacanthus paru. Age was solely determined by sectioned otoliths. All tetracycline‐treated otoliths were 1 year of age and revealed a clear fluorescent mark when observed under UV light. Otolith weight increased exponentially with standard length, and linearly with age, indicating that otolith growth continues with age and is independent of size. Age of fish in the sample ranged from 1 to 27 years. The von Bertalanffy growth equation was TLt = 36.33 (1 ? e^{?0.12 (t + 0)}). Total rate mortality (Z) was estimated to be 0.10. Attaining maximal size slowly, P. paru has a long life expectancy. Most linear growth is achieved within approximately 74% of the lifetime of the fish. Besides being an important ornamental species, P. paru has been commonly captured for decades as bycatch in trap fisheries. These growth parameters should be used with the purpose of managing fisheries targeting this species before more meaningful limits can be imposed. In the aquarium trade management, it is suggested that conservationist issues should be based on capture‐per‐area and the establishment of protected areas.     

Using otolith shape and morphometry to identify four Alburnus species (A. chalcoides,A. escherichii,A. mossulensis and A. tarichi) in Turkish inland waters

Asteriscus otolith shapes as well as their morphometry and shape contours were investigated in order to identify four allopatric Alburnus species: A. chalcoides (Güldenstädt, 1772) (Ordu), A. escherichii Steindachner, 1897 (Eski?ehir), A. mossulensis Heckel, 1843 (Tunceli), and A. tarichi (Güldenstädt, 1814) (Van) in Turkish inland waters. These were compared using the shape indices (form factor, roundness, circularity, ellipticity, rectangularity and aspect ratio), and the morphological characters [otolith weight (OWE), otolith length (OL), otolith width (OW), otolith perimeter (OP), and otolith area (OA)]. The overall canonical discriminant analysis (CDA) classification score was 93.8%, with the lowest score for A. escherichii (82.5%) and the highest for A. chalcoides (100%). The otolith shapes, morphology and shape contours of all sampled fish were a clear species differentiator, thereby demonstrating that the otolith shape is species‐specific. The current study presents for the first time comprehensive variation information on interspecific left‐right asteriscus otoliths in males and females of each Alburnus species: A. chalcoides from Ordu, A. escherichii from Eski?ehir, A. mossulensis from Tunceli and A. tarichi from Van, based on a total of 307 individuals. Scanning electron microscopy (SEM) images, shape contours and other otolith characters vary within the same genus; these differences should be investigated not only in other freshwater fish species or genera but also in the same species living in different habitats. In addition, further investigation is required not only with respect to the morphometry, biometry, shape, geometry, and shape contours of the otoliths, but also regarding the genetic methods for robust identification of various sympatric and allopatric fish populations.     

Niche partitioning and morphospace in early stages of two sympatric Diogenichthys species (Myctophidae)

Diet and morphospace of larval stages of two sympatric lanternfish Diogenichthys atlanticus and D. laternatus from the south-east Pacific Ocean were compared and the covariance between both variables was assessed for each species. Diogenichthys atlanticus stomach contents consisted mainly of copepod nauplii and digested remains and this species had a broader niche than D. laternatus, in which stomach contents were highly digested. No dietary overlap was found between both species. The covariance between skull shape and diet for D. atlanticus was given by a wider mouth gape related to the presence of copepod nauplii, whilst for D. laternatus, a shorter snout and posteriorly displaced eye were related to the presence of highly digested stomach contents. Interspecific differences between diets and skull shapes suggest that both species may have undergone morphological or niche divergence to avoid competition, such as feeding at different hours or depth stratification.     

Rapid growth and short life spans characterize pipefish populations in vulnerable seagrass beds

The life‐history traits of two species of pipefish (Syngnathidae) from seagrass meadows in New South Wales, Australia, were examined to understand whether they enhance resilience to habitat degradation. The spotted pipefish Stigmatopora argus and wide‐bodied pipefish Stigmatopora nigra exhibit some of the shortest life spans known for vertebrates (longevity up to 150 days) and rapid maturity (male S. argus 35 days after hatching (DAH) and male S. nigra at 16–19 DAH), key characteristics of opportunistic species. Growth rates of both species were extremely rapid (up to 2 mm day^?1), with seasonal and sex differences in growth rate. It is argued that short life spans and high growth rates may be advantageous for these species, which inhabit one of the most threatened marine ecosystems on earth.     

Morphology and ontogenetic changes in otoliths of the mesopelagic fishes Ceratoscopelus maderensis (Myctophidae), Vinciguerria attenuata and V. poweriae (Phosichthyidae) from the Strait of Messina (Mediterranean Sea)

Fish otoliths morphology is an important aid in taxonomic, phylogenetic, palaeoichthyological and dietary studies. This study compares the morphology of the otoliths of the myctophid species, Ceratoscopelus maderensis, and two phosichthyid species, Vinciguerria attenuata and V. poweriae, collected from the Strait of Messina in the central Mediterranean Sea to identify the most appropriate taxonomical characters that separate these species. Ontogenetic changes in the otoliths of the studied fishes are evident. The sagitta of the juvenile C. maderensis is the most similar to the adult otoliths, while otoliths of the juvenile V. poweriae are the least similar to the adult otoliths. A discussion on possible geographical variations in otolith's morphology is provided by comparing our results with sagitta's images of C. maderensis, V. attenuata and V. poweriae in other studies.     

Forensic biological pursuits of exotic fish origins: piranha in Hawaii

Synopsis The otoliths of an adult red-bellied piranha, Pygocentrus nattereri, captured from a reservoir in Hawaii were scrutinized to determine the fish's origin and growth history. Sagittal otoliths of the piranha, P. nattereri, contained internal microincrements visible by Scanning Electron Microscopy. The medial cross sectional plane of the sagitta was resolved to provide counts for the most visible micro-increments. An opportune spawning of confiscated adults provided samples for verification of daily increment formation. Daily formation of microincrements was verified from hatched individuals, and confirmed the suitability of otoliths for revealing daily patterns in the age and growth of piranhas. The central area of the sagitta was diffuse in regards to otolith microstructure and indicated the fish was held in an unchanging environment (aquarium). Therefore, otoliths provide important life history or forensic information incorporated within their structural components. The visualization of daily microincrements in the otolith of a juvenile allowed the determination of age at and since release. Fish grew rapidly after being released into the wild. From otolith increments the date of release for an individual fish can be calculated with acceptable accuracy. As presented, otolith structural information can provide age and growth data which are essential to the management of introduced species.