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Growth is a fundamental biological process, driven by a multitude of intrinsic (within-individual) and extrinsic (environmental) factors, that underpins individual fitness and population demographics. Focusing on the comprehensive information stored in aquatic and terrestrial organism hard parts, we develop a series of increasingly complex hierarchical models to explore spatial and temporal sources of growth variation, ranging in resolution from within individuals to across a species. We apply this modeling framework to an extensive data set of otolith increment measurements from tiger flathead (Platycephalus richardsoni), a demersal commercially exploited fish that inhabits the warming waters of southeast Australia. We recreated growth histories (biochronology) up to four decades in length from seven fishing areas spanning this species' range. The dominant pattern in annual growth was an age-dependent, allometric decline that varied among individuals, sexes, fishing areas, years, and cohorts. We found ev...

This study tests the sensitivity of genetically based pest control options based on sex ratio distortion to intra- and intersexual aggressive interactions that affect male and female survival and fitness. Data on these interactions and their impacts were gathered for the mosquitofish Gambusia holbrooki (Poeciliidae), a promiscuous species with a strongly malebiased operational sex ratio and well-documented male harassment of females. The experimental design consisted of an orthogonal combination of two population densities and three sex ratios, ranging from strongly male-biased to strongly female-biased, and longterm observations of laboratory populations. Contrary to expectations, the number of males in a population had little evident effect on population demographics. Rather, the density of adult females determined population fecundity (as a result of a stock-recruitment relationship involving females, but not males), constrained male densities (apparently as a result of cannibalism or intersexual aggression), and regulated itself (most likely through effects of intrasexual aggression on female recruitment). The principal effect of males was to constrain their own densities via effects of male-male aggression on adult male mortality rates. Through use of a realistically parameterized genetic/demographic model, we show that of three different genetic options applied to control G. holbrooki, one based on recombinant sex ratio distortion (release of Female Lethal carriers) is marginally more efficient than a sterile male release program, and both outperform an option based on chromosomal sex ratio distortion (Trojan W). Nonlinear dependence of reproductive rate on female density reduces the efficacy of all three approaches. The major effect of intra- and intersexual aggression is mediated through females, whose interactions reduce female numbers and increase the efficacy of a control program based on sex ratio. Socially mediated male mortality has a small impact on control programs due to operational sex ratios that are heavily male-biased. The sensitivity of sex ratio-based control options to social factors will depend on the mating system of the targeted pest, but evidence of widespread density-dependent population regulation suggests that, for most species, the effects of elevated adult mortality (due to intra- and intersexual aggression) on control programs are likely to be slight. © 2013 by the Ecological Society of America.

Based on a series of correlations and the results of several experimental series on the territorial behavior of the threespot damselfish Eupomacentrus planifrons, a two-component system of the causation of territorial aggression is proposed. The first component, spatial commitment, determines the size of the area defended; the second, attack readiness, determines the vigor of such defense. The two differ in their responses to such factors as social isolation and repeated conspecific stimulation (and stimulation from non-related fishes). By their interaction, these two independent systems can account for not only many of the apparently contradictory results reported in the literature concerning the causation of aggressive behavior (such as the effects of social isolation), but also the stability of social systems based on territoriality. Forms of territorial advertisement, such as bird song and poster-coloration, are considered in terms of this two-component system.

We examined site differences in the elemental composition of the primordium and ontogenetic variability of Sr in otoliths of fish from Australia and New Zealand and, as an out-group, the North Atlantic. Differences among sites in primordium composition are slight, but significant for all five elements assayed (Sr, Pb, Cu, Zn and Hg), but principally reflect differences between the North Atlantic and SW Pacific specimens, do not replicate for independent samples in the SW Pacific and constitute a poor “natural tag” in roughy, with

The oceanographic consequences of climate change are increasingly well documented, but the biological impacts of this change on marine species much less so, in large part because of few long-term data sets. Using otolith analysis, we reconstructed historical changes in annual growth rates for the juveniles of eight long-lived fish species in the southwest Pacific, from as early as 1861. Six of the eight species show significant changes in growth rates during the last century, with the pattern differing systematically with depth. Increasing temperatures near the ocean surface correlate with increasing growth rates by species found in depths 1,000 m) species have declined substantially during the last century, which correlates with evidence of long-term cooling at these depths. The observations suggest that global climate change has enhanced some elements of productivity of the shallow-water stocks but also has reduced the productivity, and possibly the resilience, of the already slow-growing deep-water species.

Atmospheric circulation in the southern mid-latitudes is dominated by strong circum-Antarctic zonal west winds (ZWW) over the latitude range of 35 to 60°S. These winds exhibit coherent seasonal and interannual variability, which has been related both to Antarctic (e.g. polar ice) and low-latitude climate (e.g. El Nino–southern oscillation) parameters. Historical and recent studies suggest that, at its northern margins, variability in the ZWW also has a marked quasi-decadal component. Analysis of sea-level pressure and rainfall data for the Australian region, South Africa and South America confirms frequent indications of quasi-decadal variability in parameters associated with the ZWW, which appears to be in phase around the hemisphere. This variation broadly correlates with the sunspot cycle, and specifically appears to reflect sunspot-correlated, seasonally modulated shifts in the latitude range each year of the sub-tropical ridge over eastern Australia. Sunspot-correlated variability in the southern mid-latitudes is likely to have substantial effects on temperate climate and ecology and is consistent with recent models of solar effects on upper atmospheric climate, though the mechanisms that link these to winds and rainfall at sea level remain obscure. Copyright © 2002 Royal Meteorological Society

The elemental composition of otoliths is increasingly being examined as a means of resolving the fine scale stock and population structure of fishes. The technique has been applied to three sets of problems: (1) discriminating between marine and freshwater populations (or life history stages), (2) determining links between natal rivers or nursery areas and adult stocks, and (3) assessing population structure in marine fishes. Thus far, there are few consistent patterns in the data. Diagnostic elements differ between species and systems; experimental and correlative studies provide little support for strong environmental effects on otolith composition (other than effects of extreme differences in salinity/strontium concentrations); and the physiological mechanisms that would allow such an effect for most elements are not well documented. The area of investigation suffers from: a lack of well-established benchmark studies against which ‘reality’ of results can be assessed; small sample sizes and incomplete analysis; and non-critical evaluation of results. Two areas of research look promising: the use of marked differences between marine and freshwater fishes (or the corresponding portions of otoliths of anadromous fish) in strontium concentrations to track migrating coastal fishes, and apparently robust indications of regional structuring of some marine fish populations. The relative youthfulness of the field dictates the need for work in a number of areas, but priorities at this stage should include developing a better understanding of the physiological mechanisms that determine otolith composition and its variability, including distinguishing the effects of handling and contamination from ‘real’ composition, and validating apparent patterns of stock structure both by independent replication of results and comparisons against other sources of information, such as genetic and tagging studies. To assure data quality and form a base for corroboration of results, widespread use of certified reference materials and careful documentation of analytic procedures are essential.

The use of otolith chemistry as a tool for analysing the biology of fishes assumes that the procedures used to collect and prepare otoliths for analysis do not alter their composition. With otoliths of Nemadactylus macropterus, Hoplostethus atlanticus, and Rhombosolea tapirina, we show that this assumption is not valid for the elements that can be detected using electron-probe microanalysers (those present at concentrations greater than ≃100 parts per million): all six elements routinely measured using these techniques were affected by at least one post-mortem procedure tested. Measured concentrations of calcium and strontium were relatively insensitive to most procedures tested, whereas concentrations of sodium, potassium, sulphur and chlorine were affected substantially by many commonly used procedures. The ease with which otolith composition could be modified post-mortem suggests that apparent geographic, habitat-specific or ontogenetic differences in otolith composition should be interpreted with extreme caution because of easily induced artefacts and the problem of pseudo-replication associated with the ways otoliths are sampled and prepared for analysis.

Analysis of the chemistry of calcified tissues has been suggested to be a source of useful information on the population structure and environmental history of fishes. We have investigated this approach as a means of determining the number of spawning areas and diversity of migration routes in the large pelagic scombrid, Thunnus maccoyii (southern bluefin tuna). Analysis was based on ontogenetic variation in the composition of sagittal otoliths, as measured using two probe microanalysers (wavelength dispersive electron probe microanalysis and proton-induced X-ray emission microanalysis), of 9 larvae collected on the single known spawning ground (NE Indian Ocean), of 29 juveniles caught at different points along the known migration routes (off western Australia, southern Australia, and South Africa), and of 14 adults caught in the high-seas fishery (off SE Australia). Fifteen elements were detected in T. maccoyii sagittae, but only six (Ca, Na, Sr, K, S, and Cl) were consistently present at concentrations above minimum detection limits. No attempt was made to measure the concentrations of C, N and O, which are assumed to also be present. Comparisons among different samples indicated that: (1) variation in the composition of the otolith primordium was unimodal and, generally, normally distributed; (2) this composition varied among specimens as a function of their size or, apparently, year-class; (3) individuals collected from widely separated locations did not differ clearly in the composition of the most recently deposited sections of their otoliths; and (4) all variation in the composition of adult otoliths was encompassed in the range of variation of juveniles collected along the major known migration route. These observations are consistent with the hypothesis of a single spawning area for T. maccoyii, but also indicate that the range of environmentally correlated variation in composition is too low to provide a robust test of the diversity of migration routes. It is not clear why this variation is so low, but we suspect that it reflects both the relative homogeneity of the pelagic environment and a weak effect of environmental factors on the concentration of elements present in otoliths at levels≳1 ppm.

The deleterious effects of tributyltin (TBT) on spermiation in fish have been attributed to its role in inhibiting aromatisation of androgens to estrogens, and the critical role of the latter in sperm development. We test this hypothesis by examining sperm parameters, fertilisation and hatching success in males of two fish species exposed throughout life to doses of Fadrozole, a non-steroidal aromatase inhibitor (AI), provided in their diets. AI-treatment caused 100% male development in zebrafish, but only partial masculinisation in medaka, in both cases supporting previous studies and suggesting different roles of estrogen in sexual differentiation in the two species. Milt volume, initial sperm motility, maximum sperm swimming duration and sperm morphology did not differ significantly between Control and AI-dosed fish in either species, after excluding low milt volumes in sex-changed females in medaka. Fertilisation rates were also unaffected by the aromatase inhibition, but hatching success in medaka was 31% lower than in Control males, suggesting a previously unreported effect of aromatase on sperm quality. The slight effect of aromatase inhibition on sperm parameters in general contrasts with the marked effect of TBT on fish sperm, and suggests that a mechanism other than depressed estrogen levels is involved.

Electron probe microanalyzers fitted with energy-dispersive (ED) and wavelength-dispersive (WD) X-ray spectrometers are the standard instruments for measuring microscale differences in the chemical composition of the calcified tissues of fishes. We review the principles of using these spectrometers, detail procedures for preparing otoliths for microanalysis, and compare the accuracy and sensitivity of the two instruments. ED systems on electron probes are prone to produce spectral artifacts, peak overlaps and difficulties in modelling nonlinear backgrounds. Current generation ED systems do not, therefore, appear suitable for quantitative analysis of trace elements ( 3μW · μm−2 resulted in unacceptable levels of specimen damage.

Micro-PIXE has been used to measure the trace element distribution in otoliths from several species of ocean fish, in order to investigate its possible use in stock discrimination. Trace elements detected include Sr, Fe, Mn, Ni, Zn, Cu, Se, Cd, Br, Hg and Pb. Trace elements Na, K, Cl, S and Cl were detected with the electron microprobe. The high sensitivity of PIXE demands a meticulous sample preparation procedure to avoid contamination problems. Practical problems associated with the application of the technique were investigated in detail. Preliminary results indicate that most trace elements except Sr, are present at close to the limits of detection at few ppm, but biologically significant data can be obtained for stock discrimination applications.

Brood-directed parental aggression, in which parents attack and even kill their own young, is described for the coral reef fish Acanthochromis polyacanthus . This behaviour involves both parents, occurs on days 7–16 post-hatching, and is characteristic of all broods produced early in the spawning season. Such parental aggression appears to underlie widespread early brood loss in the species, i.e. disappearance of young before they reach an age at which they are viable in the absence of parental defence. Simultaneously, there is also a high frequency of sudden increases in the sizes of some tended broods. The data suggest that some brood-tending parents are forcibly expelling their broods from parental territories, and fostering them on to adults still tending broods. By expelling their young and re-spawning, pairs may realize a 7% increase in annual fecundity over pairs that do not expel their young, despite a low survival rate of expelled young.

The elemental composition of fish otoliths is of considerable interest to those who wish to reconstruct temperature, migration, or environmental histories of individual fish based on assays of the otolith growth sequence. However, reported differences in otolith elemental composition among studies may be due in part to performance differences among four of the most popular instruments for targeted elemental analysis: wavelength-dispersive electron microprobe (WD-EM), energy-dispersive electron microprobe (ED-EM), proton-induced X-ray emission (PIXE), and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). To rigorously compare the sensitivity, accuracy, and precision of these four analytical tools, the International Otolith Composition Experiment distributed blind-labelled real and artificial otoliths of known but varied elemental composition to eight laboratories for assay of 10 selected elements. No one instrument type was sensitive to each element, nor was any one instrument preferred for use in all assays. In general however, abundant elements such as Na and K could only be measured accurately with an electron microprobe, while the trace elements required PIXE or LA-ICPMS. Strontium could be measured with considerable accuracy and precision by WD-EM, PIXE, and LA-ICPMS. The presence of significant, and occasionally large, differences among laboratories suggests that comparisons among published studies should be made cautiously and only after appropriate calibration.