Mediterranean juvenile bluefin tuna: life history patterns

As there is a lack of information on the growth and migrations of bluefin tuna, information about them was gathered using the structural and chemical characteristics of their otoliths and mercury levels in body tissues as indicators of physiological and habitat characteristics. The otoliths of juvenile tuna caught in the Spanish Mediterranean littoral were studied. Otolith increments, assumed to be formed daily, were enumerated. Measurements by wavelength dispersive electron microprobe confirmed the presence of strontium in otolith tissue, and an inverse relationship between strontium/calcium (Sr/Ca) concentration ratio and temperature is suggested. Electron microprobe analyses combined with daily increment analyses of otoliths provided life history profiles for individual fish. Additional Sr/Ca concentration ratio data on fish supported the idea that Sr/Ca ratios can provide information on the environmental history of individual fish. Body concentrations of mercury were related to otolith analyses to suggest age structure, critical life history periods, growth environment, stock structure, food web position, and migration history. The techniques applied present an innovative approach to management-related problems, and the combination of chemical analyses with structural analyses promises to expand our knowledge of the life history of migratory fishes.     

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.     

L'otolithe: la ≪ boîte noire ≫ des Téléostéens

Calcified structures such as otoliths have been used successfully for estimating the age of teleost fishes for many years. Otoliths record age as well as annual and/or seasonal events in the lives of fish and they are an important source of life history information. Otoliths have been found to contain characteristics that are stock specific. Elemental composition might be useful for identifying non-mixing groups of fish that may be regarded as separate stocks for fisheries management. Examination of otolith microstructure has been used to study early life history. Papers describe the use of otolith microstructure combined with chemical analysis to assess the relative significance of environmental variables: feeding frequency, photoperiod and temperature, migration from freshwater to marine water, pollution, etc. Otoliths are the first calcified structures that appear during the early development of fish and they provide a more adequate record of the growth history than scales. Otoliths represent the black box of teleost fish.     

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.     

Electron microprobe analysis of juvenile walleye pollock,Theragra chalcogramma,otoliths from Alaska: a pilot stock separation study

Synopsis The incorporation of dissolved oceanic constituents in the otoliths of fish has potential as a chemical tracer for reconstructing the early life history of marine fish. Wavelength dispersive spectrometers on an electron microprobe were used to measure Na, Mg, P, S, Cl, K, Ca, and Sr concentrations on the outer margins of 57 juvenile walleye pollock, Theragra chalcogramma, otoliths from five locations in the Gulf of Alaska and Bering Sea. Discriminant analyses that used various combinations of Na, P, K, Sr, and fish standard length and/or age showed that 60–80% of the samples could be assigned to the correct capture locality. While the concentrations of some of the measured elements correlated with standard length or age of the fish, there are measurable differences among localities when concentrations are length or age corrected, mainly due to differences in Na and K concentrations. Elemental composition of otoliths potentially could be used to assign fish from a mixed stock fishery to original stocks, information that is greatly needed for the effective management of fish stocks.     

Age validation,and comparison of otolith,vertebra and opercular bone for estimating age of <Emphasis Type="BoldItalic">Schizothorax o’connori</Emphasis> in the Yarlung Tsangpo River,Tibet

A collection of 514 Schizothorax o’connori was made between August 2008 and August 2009 from Yarlung Tsangpo River to assess the suitability of three bony structures for age estimation. The annulus characteristics of otolith, vertebra and opercular bone were described. Location of the first annulus was validated by daily growth increment (DGI) analysis in the otoliths. Annual periodicity was verified by marginal increment ratio (MIR) analysis in otoliths and edge analysis in vertebrae and opercular bones. Annuli formed, once a year, between March and May for all three bony structures. Otoliths, vertebrae and opercular bones were examined to determine which structure produced the most precise and accurate age estimates in S. o’connori. Vertebrae and otoliths matched closely for the first 21 years of life, while opercular bones appeared to underestimate age. For older fish, the counts diverged and otoliths consistently providing higher age estimates. Sectioned otoliths proved to be the most precise and accurate structure for age estimation. The oldest observed schizothoracine fish was 50, more than twice the longevity previously accepted in S. o’connori.     

Interactive effects of ontogeny, food ration and temperature on elemental incorporation in otoliths of a coral reef fish

The potential for environmental and physiological modification of elemental incorporation in otoliths is significant and must be validated before otoliths can be used reliably to estimate water parameters over the life history of a fish. We experimentally manipulated temperature and diet quantity for juvenile, sub-adult, and adult Acanthochromis polyacanthus, a tropical damselfish of the SW Pacific. Significant interactive effects between life history stage, temperature and food quantity were observed for otolith Ba/Ca, while significant interactions between stage and food were observed for Sr/Ca. Specific growth rates were negatively correlated with D_Ba and D_Sr for juveniles and sub-adults. These interactions indicated elemental incorporation dynamics varied depending on the life history stage, suggesting variation in effects of stage-specific metabolism or reproductive status. Our results highlight complex responses of elemental incorporation to both endogenous and exogenous factors. Interpretations of life history transects across otoliths must account for these effects to avoid confounding environmental variability with ontogenetic changes in physiology.     

Use of otolith chemistry to examine patterns of diadromy in the threatened Australian grayling Prototroctes maraena

Otolith chemical analyses (proton-induced X-ray emission and laser ablation inductively coupled plasma mass spectrometry) were used to examine patterns of diadromy in Australian grayling Prototroctes maraena collected from three rivers in south-eastern Australia. Concentrations of Sr:Ca and Ba:Ca were measured in the sagittal otoliths of 25 fish and in water samples collected on two occasions from multiple sites within freshwater, estuarine and marine reaches of the rivers. The results provide evidence of marine residency during the juvenile phase, with high Sr:Ca and low Ba:Ca in the inner region of the otoliths that were consistent across all three rivers. This general pattern was apparent for all individuals examined, suggesting that diadromous migration may be an obligate aspect of the life history. The chemical signatures of the outer regions of the otoliths were distinct between the three rivers, whilst there was no difference in the inner regions of the otoliths. This suggests that juveniles from different rivers may reside in a relatively homogenous chemical environment, such as the sea, and populations in coastal Victorian rivers may share a common marine recruitment source.     

Strontium-calcium concentration ratios in fish otoliths as environmental indicators

• 1.1. External and internal examinations of otoliths in fishes for macrostructure and microstructure has demonstated yearly, daily and population rhythmic patterns.
• 2.2. Chemical analyses (atomic absorption) of otolith carbonate from reared Fundulus heteroclitus for strontium-calcium concentration ratios demonstrated changes in chemistry related to temperature.
• 3.3. Microprobe analyses made it feasible to interpret almost daily changes in temperature to provide the temperature history of an individual fish.
• 4.4. A combination of microprobe analyses and daily increment analyses of otoliths can provide a life history profile for individual fish and can provide information on the environmental history of each fish.
• 5.5. Such information is vital to our understanding of the processes underlying recruitment and growth rates, and would make it possible to link growth and mortality rates to environmental occurrences.

     

Validation of the periodicity of increment formation in the otoliths of a cichlid fish from Lake Tanganyika, East Africa

Tetracycline was used as a chemical tag in a mark‐recapture study to examine the pattern of increment formation in the otoliths of Tropheus moorii , a rock‐dwelling cichlid from Lake Tanganyika. A total of 256 fish were captured by divers and injected with tetracycline. Of these, nine were recaptured after either 1 or 2 years at liberty and eight retained tags within their otoliths. Comparison of the number of growth increments formed after the tag and the time at liberty demonstrated that increments were deposited on an annual basis in the otoliths of this species. Furthermore, there was a strong relationship between otolith mass and age suggesting that otoliths grew at a predictable rate throughout the life of the fish. Validation of an annual pattern of increment deposition allowed age and growth information to be derived from otoliths. This showed that T. moorii grew rapidly to attain adult size by 3 years of age. Males grew faster than females and also attained a larger size than females (8·74 v . 7·91 cm L _S respectively). The longevity of some of these small freshwater fish was surprising; the oldest individual had an age of 10 years, while the average age of adults was 4 years.     

Assessing the role of ontogenetic movement in maintaining population structure in fish using otolith microchemistry

Identifying the mechanisms maintaining population structure in marine fish species with more than a single dispersing life stage is challenging because of the difficulty in tracking all life stages. Here, a two‐stage otolith microchemistry approach to examining life‐stage movement was adopted, tracking a year‐class from the juvenile to adult stage and inferring larval sources from clustering, in order to consider the mechanisms maintaining population structuring in North Sea cod. Clustering of near‐core chemistry identified four clusters, two of which had either a southern or northern affinity and were similar to juvenile edge chemistry. The other two clusters, common to the central North Sea, had intermediate chemical composition and may have reflected either larval mixing in this region or a lack of geographic heterogeneity in the elemental signature. From the comparison of whole juvenile and the corresponding component of adult otoliths, adults from the southern North Sea mostly recruited from adjacent nursery grounds. In contrast, many adults in the northern North Sea had a juvenile chemistry consistent with the Skagerrak and juveniles from the northern Skagerrak site had a near‐core chemistry consistent with the northern North Sea. Similarities in otolith chemistry were consistent with retention of early life stages at a regional level and also juvenile and adult fidelity. The links between the northern North Sea and Skagerrak indicate natal homing, which when considered in the context of genetic evidence is suggestive of philopatry. The approach used here should be useful in exploring the mechanisms underlying population structuring in other species with multiple dispersive life stages and calcified hard parts.     

Age and terminal reproductive attempt influence laying date in the thorn‐tailed rayadito

Age‐specific variation in reproductive effort can affect population dynamics, and is a key component of the evolution of reproductive tactics. Late‐life declines are a typical feature of variation in reproduction. However, the cause of these declines, and thus their implications for the evolution of life‐history tactics, may differ. Some prior studies have shown late‐life reproductive declines to be tied to chronological age, whereas other studies have found declines associated with terminal reproduction irrespective of chronological age. We investigated the extent to which declines in late life reproduction are related to chronological age, terminal reproductive attempt or a combination of both in the thorn‐tailed rayadito Aphrastura spinicauda, a small passerine bird that inhabits the temperate forest of South America. To this end we used long‐term data (10 years) obtained on reproductive success (laying date, clutch size and nestling weight) of females in a Chilean population. Neither chronological age nor terminal reproductive attempt explained variation in clutch size or nestling weight, however we observed that during the terminal reproductive attempt older females tended to lay later in the breeding season and younger females laid early in the breeding season, but this was not the case when the reproductive attempt was not the last. These results suggests that both age‐dependent and age‐independent effects influence reproductive output and therefore that the combined effects of age and physiological condition may be more relevant than previously thought.     

Compressed vertebrae in Atlantic salmon Salmo salar: evidence for metaplastic chondrogenesis as a skeletogenic response late in ontogeny

Anterior/posterior (a/p) compression of the vertebral column, referred to as 'short tails', is a recurring event in farmed Atlantic salmon. Like other skeletal deformities, the problem usually becomes evident in a late life phase, too late for preventive measures, making it difficult to understand the aetiology of the disease. We use structural, radiological, histological, and mineral analyses to study 'short tail' adult salmon and to demonstrate that the study of adult fish can provide important insights into earlier developmental processes. 'Short tails' display a/p compressed vertebrae throughout the spine, except for the first post-cranial vertebrae. The vertebral number is unaltered, but the intervertebral space is reduced and the vertebrae are shorter. Compressed vertebrae are characterized by an unchanged central part, altered vertebral end plates (straight instead of funnel-shaped), an atypical inward bending of the vertebral edges, and structural alterations in the intervertebral tissue. The spongiosa is unaffected. The growth zones of adjacent vertebrae fuse and blend towards the intervertebral space into chondrogenic tissue. This tissue produces different types of cartilage, replacing the notochord. The correspondence in location of intervertebral cartilage and deformed vertebral end plates, and the clearly delimited, unaltered, central vertebral parts suggest that the a/p compression of vertebral bodies is a late developmental disorder that may be related to a metaplastic shift of osteogenic tissue into chondrogenic tissue in the vertebral growth zone. Given the lack of evidence for infections, metabolic disorders and/or genetic disorders, we propose that an altered mechanical load could have caused the transformation of the bone growth zones and the concomitant replacement of the intervertebral (notochord) tissue by cartilaginous tissues in the 'short tails' studied here. This hypothesis is supported by the role that notochord cells are known to play in spine development and in maintaining the structure of the intervertebral disk.     

Age at recruitment of Hawaiian freshwater gobies

Synopsis Very little is known about the dynamics of native Hawaiian stream fishes. Five species are restricted, as adults, to freshwater streams and estuaries on the major islands of the Hawaiian archipelago. This paucity of information is partly due to difficulties inherent in determination of age and subsequent determinations of life history characteristics. In the present study, we determined the age of newly recruited Hawaiian gobies,Stenogobius genivittatus andAwaous stamineus using otolith microtechniques. Internal otolith increments were enumerated using scanning electron microscopy (SEM). Increments of newly recruited juveniles were deposited on a daily basis as validated through a marking study. Results showed recruitment at an average age of 135 and 161 days for these two species, respectively, with more rapid growth following recruitment to freshwater. Chemical analyses of otolith carbonate of the Hawaiian gobies by electron microprobe for strontium and calcium concentrations provided valuable insights into a fish's past history. A combination of structural and chemical analyses makes it possible to link growth and recruitment to nutritional and environmental factors. Such information developed as a broad model would be applicable to the management of Hawaiian gobies and would greatly improve the quality of information available for these unique fish populations and other fish populations     

All in the ears: unlocking the early life history biology and spatial ecology of fishes

Obtaining biological and spatial information of the early life history (ELH) phases of fishes has been problematic, such that larval and juvenile phases are often referred to as the ‘black box’ of fish population biology and ecology. However, a potent source of life‐history data has been mined from the earstones (otoliths) of bony fishes. We systematically reviewed 476 empirical papers published between 2005 and 2012 (inclusive) that used otoliths to examine fish ELH phases, which has been an area of increasing attention over this period. We found that otolith‐based research during this period could be split into two broad themes according to whether studies examined: (i) biological objectives related to intrinsic processes such as larval and juvenile age, growth and mortality, and/or (ii) spatial objectives, such as habitat use, dispersal and migration. Surprisingly, just 24 studies (5%) explored a combined biological–spatial objective by simultaneously exploiting biological and spatial information from otoliths, suggesting much more scope for such integrated research objectives to be answered via the use of multiple otolith‐based techniques in a single study. Mapping otolith analytical techniques across these two approaches revealed that otolith structural analysis was mainly used to investigate biological processes, while otolith chemical analyses were most often applied to spatial questions. Heavy skew in research effort was apparent across biomes, with most (62%) publications specific to marine species, despite comparable levels of species richness and the importance of freshwater taxa (just 15% of papers). Indeed, around 1% (380 species) of a possible 31400+ extant species were examined in our surveyed papers, with a strong emphasis on temperate marine species of commercial value. Potential model species for otolith‐based ELH ecology research are arising, with the eel genus Anguilla (24 studies) and the European anchovy Engraulis encrasicolis (14 studies) attracting more research effort than most other taxa. While there is a preponderance of common techniques (e.g. daily otolith increment counts, increment widths), novel techniques such as transgenerational marking and computed X‐ray tomography, are increasingly being applied in published studies. The application of an integrative approach based on a combination of emerging techniques and traditional methods holds promise for major advances in our understanding of ELH fish ecology and to shine light into the ‘black box’ of fish ecology.     

Seeking the true time: Exploring otolith chemistry as an age-determination tool

Fish otoliths' chronometric properties make them useful for age and growth rate estimation in fisheries management. For the Eastern Baltic Sea cod stock (Gadus morhua), unclear seasonal growth zones in otoliths have resulted in unreliable age and growth information. Here, a new age estimation method based on seasonal patterns in trace elemental otolith incorporation was tested for the first time and compared with the traditional method of visually counting growth zones, using otoliths from the Baltic and North seas. Various trace elemental ratios, linked to fish metabolic activity (higher in summer) or external environment (migration to colder, deeper habitats with higher salinity in winter), were tested for age estimation based on assessing their seasonal variations in concentration. Mg:Ca and P:Ca, both proxies for growth and metabolic activity, showed greatest seasonality and therefore have the best potential to be used as chemical clocks. Otolith image readability was significantly lower in the Baltic than in the North Sea. The chemical (novel) method had an overall greater precision and percentage agreement among readers (11.2%, 74.0%) than the visual (traditional) method (23.1%, 51.0%). Visual readers generally selected more highly contrasting zones as annuli whereas the chemical readers identified brighter regions within the first two annuli and darker zones thereafter. Visual estimates produced significantly higher, more variable ages than did the chemical ones. Based on the analyses in our study, we suggest that otolith microchemistry is a promising alternative ageing method for fish populations difficult to age, such as the Eastern Baltic cod.     

Age and growth of the common carp, Cyprinus carpio, in the River Murray, Australia: validation, consistency of age interpretation, and growth models

The present study validates age estimates from a suite of calcified structures (scales, opercular bones and otoliths), assesses the consistency of age interpretations and evaluates growth models in common carp from the lower Murray River, Australia. Marginal increment analysis was used to validate annulus counts, with attention to the 'edge interpretation problem'. The formation of annuli occurred annually after pooling annulus groups, and in carp 4 and 5 years old. The regular alternation of opaque and translucent zones in opercular bones and whole otoliths of younger and older carp was also suggestive of annual periodicity. From systematic comparisons, the use of both opercular bones and whole otoliths in routine age determinations is recommended. Six growth models, including the von Bertalanffy growth function (VBGF) and five polynomial curves were tested to describe growth in length. A log-log quadratic function, by virtue of its precision, and the VBGF, with wider applicability and more biological realism, were chosen.     

Clastic cells: mineralized tissue resorption in health and disease

Clastic cells are responsible for mineralized tissue resorption. Bone resorbing cells are called osteoclasts; however, they are able to resorb mineralized dental tissues or calcified cartilage and then they are called odontoclasts and chondroclasts, respectively. They derive from mononuclear precursors of the monocyte-macrophage lineage from hemopoietic tissue, reach target mineralized tissues and degrade them under many different physiologic or pathologic stimuli. Clastic cells play a key role in calcium homeostasis, and participate in skeletal growth, tooth movement, and other physiological and pathological events. They interact tightly with forming cells in bone and dental hard tissues; their unbalance may result in disturbed resorptive activity thus, causing local or systemic diseases.     

Rhythmic structural and chemical patterns in otoliths of the Antarctic fish Notothenia larseni: Their application to age determination

Summary Sagittal otoliths from Notothenia larseni contain microincremental growth rings which are distinctly visible in otolith sections using Scanning Electron Microscopy. These microincrements are similar to those deposited daily in the otoliths of fishes from temperate and tropical waters. Microincrements were easily enumerated and fish length was related to increment number by a logarithmic curve. Otolith microstructure analysis appears to provide a technique to accurately determine age and growth rates in these fish. Sr/Ca ratios in otolith aragonite were analyzed along a radius from the outside edge to the core of an otolith section using an electron microprobe. The strontium/calcium (Sr/Ca) ratios varied with a cyclic periodicity apparently related to seasonal water temperature cycles and the number of cycles agreed closely with age estimated from daily microincrement counts. Sr/ca cycles can potentially be used to determine age, validate growth rates determined by other methods, and establish thermal conditions experienced during the life of a fish. Microstructural and chemical analyses of otoliths demonstrate great potential in helping to answer many questions about the growth processes and ecology of Antarctic fishes.     

Precision of age determination from otoliths,opercular bones,scales and vertebrae in the threatened freshwater snakehead,Channa punctata (Bloch, 1793)

Ages were estimated from otoliths, opercular bones, scales, and vertebrae of 514 specimens of Channa punctata from three Indian rivers – the Ganga, Gomti, and Yamuna – to evaluate the potential bias of age estimates between readers and between pairs of aging structures. Standard procedures were followed to prepare and study the age structures. Among all structures, otoliths showed highest (97.4%) values of agreement between readers' age estimates followed by the opercular bones (89.5%), scales (84.2%) and vertebrae (78.9%). Because of the highest percentage of agreement and lowest average percentage of error (0.05%) and coefficient of variation (0.76%) values between readers, otoliths were considered the most suitable aging structure for C. punctata. When otoliths ages were compared with those of the other structures viz., opercular bones, scales and vertebrae, percentage of agreement was found highest between estimates (90.8%) of otoliths and opercular bones.