A nitrogen isotopic shift in fish otolith-bound organic matter during the Late Cretaceous.

The nitrogen isotopes of the organic matter preserved in fossil fish otoliths (ear stones) are a promising tool for reconstructing past environmental changes. We analyzed the 15N/14N ratio (δ15N) of fossil otolith-bound organic matter in Late Cretaceous fish otoliths (of Eutawichthys maastrichtiensis, Eutawichthys zideki and Pterothrissus sp.) from three deposits along the US east coast, with two of Campanian (83.6 to 77.9 Ma) and one Maastrichtian (72.1 to 66 Ma) age. δ15N and N content were insensitive to cleaning protocol and the preservation state of otolith morphological features, and N content differences among taxa were consistent across deposits, pointing to a fossil-native origin for the organic matter. All three species showed an increase in otolith-bound organic matter δ15N of ~4‰ from Campanian to Maastrichtian. As to its cause, the similar change in distinct genera argues against changing trophic level, and modern field data argue against the different locations of the sedimentary deposits. Rather, the lower δ15N in the Campanian is best interpreted as an environmental signal at the regional scale or greater, and it may be a consequence of the warmer global climate. A similar decrease has been observed in foraminifera-bound δ15N during warm periods of the Cenozoic, reflecting decreased water column denitrification and thus contraction of the ocean's oxygen deficient zones (ODZs) under warm conditions. The same δ15N-climate correlation in Cretaceous otoliths raises the prospect of an ODZ-to-climate relationship that has been consistent over the last ~80 My, applying before and after the end-Cretaceous mass extinction and spanning changes in continental configuration.

Angular and Linear Accelerations, Ear, and the Skeletal Muscle.

The ear serves two vital functions of hearing and maintaining balance. It achieves these roles within three major compartments: the outer, the middle, and the inner ear. Embryological development of the ear and its associated structures have been studied in some animal models. Yet, the role of skeletal muscle in ear development and its related structures is largely unknown. Research suggests the outer ear and parts of the inner ear may require skeletal muscle for normal embryogenesis. Here, we describe the role of skeletal muscle in the development of the ear and its associated structures. Moreover, we report the possible consequences of defect in the skeletal muscle of the ear and the clinical correlates of such consequences.

Fish otoliths as biological dosimeter: internal dose calculation.

Otoliths are organs used by fish for hearing and keeping balance. They consist of biogenic crystals of hydroxyapatite and do not contain any living cells. Upon exposure to ionizing radiation, otolith hydroxyapatite accumulates radiation-induced stable CO2- radicals whose amount is proportional to absorbed dose. In electron paramagnetic resonance (EPR) dosimetry, carbonate ions are registered and, hence, the total accumulated dose in the fish otolith can be quantified. Therefore, otoliths can be used as individual fish dosimeters to support radiobiological and radioecological studies. An important aspect of otolith-based EPR dosimetry on fish from contaminated water bodies is the potential presence of bone-seeking 90Sr. Consequently, cumulative absorbed doses measured with EPR in otoliths may reflect the superposition of internal exposure to 90Sr/90Y and external exposure due to radionuclides circulating in soft tissue of the fish as well as due to environmental contamination. The objective of the present study was to develop a method that allows for an assessment of the contribution of 90Sr to the total dose in otolith. The method has been tested using otoliths from seven fish taken from reservoirs located in the Southern Urals contaminated with radionuclides including 90Sr. It has been shown that dose to otoliths is largely determined by 90Sr in the hydroxyapatite. The internal dose component can be calculated using activity concentration-to-dose conversion factors, which vary slightly in the range of 2.0-2.8 × 10-3 Gy year-1 per Bq g-1 depending on fish species and age. Internal doses to fish from water bodies with different levels of 90Sr contamination were calculated in the range from 2 mGy to ~ 200 Gy. External dose contribution was derived for two fish only to be about 100 and 40 Gy. It is concluded that EPR dosimetry on fish otoliths is a promising tool when external exposure prevails or is comparable to internal exposure due to 90Sr.

Otolith mineralogy affects otolith shape asymmetry: a comparison of hatchery and natural origin Coho salmon (Oncorhynchus kisutch).

Many aspects of natural and hatchery origin salmonid genetics, physiology, behaviour, anatomy and life histories have been compared due to the concerns about what effects domestication and hatchery rearing conditions have on fitness. Genetic and environmental stressors associated with hatchery rearing could cause greater developmental instability (DI), and therefore a higher degree of fluctuating asymmetry (FA) in various bilaterally paired characters, such as otoliths. Nonetheless, to appropriately infer the effects of DI on otolith asymmetry, otolith mineralogy must be accounted for. Vateritic otoliths differ substantially from aragonitic otoliths in terms of mass and shape and can artificially inflate any measurement of FA if not properly accounted for. In this study, measurements of otolith asymmetry between hatchery and natural origin Coho salmon Oncorhynchus kisutch from three different river systems were compared to assess the overall differences in asymmetry when the calcium carbonate polymorph accounted for 59.3% of otoliths from hatchery origin O. kisutch was vateritic compared to 11.7% of otoliths from natural origin O. kisutch. Otolith mineralogy, rather than origin, was the most significant factor influencing the differences in asymmetry for each shape metric. When only aragonitic otoliths were compared, there was no difference in absolute asymmetry between hatchery and natural origin O. kisutch. The authors recommend other researchers to assess otolith mineralogy when conducting studies regarding otolith morphometrics and otolith FA.

Utility of body and otolith morphometry to discriminate cryptic juveniles of two sympatric red snappers (Perciformes: Lutjanidae).

The sympatric red snappers, Lutjanus erythropterus and Lutjanus malabaricus, are highly valued by commercial and recreational fishers along the tropical northern coasts of Australia and throughout their distribution. Studies on the life history and ecology of these congeners are confounded by difficulties in distinguishing the cryptic juveniles of each species (i.e., < 200 mm total length). This study aimed to validate a robust and cost-effective method to discriminate these juveniles using body and/or otolith morphometric data in a multivariate analysis. Juvenile samples were collected from the northwest (n = 71) and northeast (n = 19) coasts of Australia, and species identification was confirmed using DNA barcoding. The most parsimonious multivariate models achieved accurate species prediction rates of 98.8%, which consisted of just three body variables (dorsal fin length, the distance from the snout to the anterior edge of the eye, and either jaw length or distance from the snout to the preoperculum). The high level of discrimination for these cryptic juveniles highlights the robustness of this morphometric approach. The slightly lower rate of discrimination using otolith morphology (84.9%) was associated with greater regional variation in L. malabaricus between the northwest and northeast coasts. Slight variations in otolith shape are typically used to determine stock structure, which highlights the potential need to collect samples over a broader area of a species geographic range when using an otolith morphometric discrimination model. The method outlined in this study could be applied to distinguish other cryptic congeneric fish species, including from archived otolith collections. Moreover, this method has the potential to be utilized in assessing species compositions using body measurements from in situ stereo-video.

Retinoic acid signaling regulates late stages of semicircular canal morphogenesis and otolith maintenance in the zebrafish inner ear.

BACKGROUND: The vitamin A derivative all-trans retinoic acid (RA) regulates early stages of inner ear development. As the early disruption of the RA pathway results in profound mispatterning of the developing inner ear, this confounds analyses of specific roles in later stages. Therefore, we used the temporal-specific exposure of all-trans RA or diethylaminobenzaldehyde to evaluate RA functions in late otic development. RESULTS: Perturbing late RA signaling causes behavioral defects analogous to those expected in larvae suffering from vestibular dysfunction. These larvae also demonstrate malformations of the semi-circular canals, as visualized through (a) use of the transgenic strain nkhspdmc12a, a fluorescent reporter expressed in otic epithelium; and (b) injection of the fluorescent lipophilic dye DiI. We also noted the altered expression of genes encoding ECM proteins or modifying enzymes. Other malformations of the inner ear observed in our work include the loss or reduced size of the utricular and saccular otoliths, suggesting a role for RA in otolith maintenance. CONCLUSION: Our work has identified a previously undescribed late phase of RA activity in otic development, demonstrating that vestibular defects observed in human patients in relation to perturbed RA signaling are not solely due to its early disruption in otic development.

Life history of the humpnose big-eye bream Monotaxis grandoculis.

This study provides estimates of growth rate, longevity, maturity, spawning seasonality and mortality for Hawai'i's only lethrinid, the humpnose big-eye bream (known as Mu in Hawai'i) Monotaxis grandoculis, a commercially and recreationally important species in Hawai'i and throughout the Indo-Pacific. M. grandoculis reaches maturity at 303 mm fork length or 3.6 years of age for both sexes. Males were significantly larger than females for a given age. The von Bertalanffy growth parameters for males and females were L∞  = 506 mm fork length and von Bertalanffy growth coefficient (K) = 0.24 year-1 , and L∞  = 427 mm fork length and K = 0.33 year-1 , respectively. Both males and females reached ages over 20 years old, with a maximum age of 23 years. M. grandoculis had a distinct spawning season from May through August with corresponding elevated female gonadosomatic index. An age-based multinomial catch curve indicated that the commercial exploitation rate (natural mortality/fishing mortality) was 0.48 year-1 , which is considered below the overfishing limit.

Varying frequency of vateritic otoliths in the Baltic herring Clupea harengus membras.

We report observations of vateritic crystallization in the sagittal otoliths of the Baltic herring Clupea harengus membras in the northern Baltic Sea. While the existence of vaterite in the calcium carbonate matrix of sagittal otoliths has been observed in various species globally, reports from the brackish Baltic Sea are few in number. Large variation in the frequency of vaterite in 1984, 1988, 1997, 2010 and 2017 was observed, suggesting that the phenomenon is not static and more long-term studies should be conducted in search of the ultimate causing factors.

Eyes and ears: A comparative approach linking the chemical composition of cod otoliths and eye lenses.

Fish eye lenses are a protein-based chronological recorder of microchemical constituents that are a potentially useful tool for interpretations of environmental, ecological and life-history experienced by fish. Here, we present the first study with data on the chemical composition of eye lenses from Baltic cod examined using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) and compare these spatially resolved data to otoliths from the same fish also analysed by LA-ICPMS, measuring the isotopes 27 Al, 137 Ba, 43 Ca, 52 Cr, 65 Cu, 57 Fe, 39 K, 7 Li, 25 Mg, 55 Mn, 31 P, 208 Pb, 85 Rb, 45 Sc, 29 Si, 88 Sr, 47 Ti, 50 V, 149 Yb, 66 Zn and 90 Zr. Comparison of the variation in element concentrations between eye lenses and otoliths from the same individuals showed minor similarities, suggesting a different governance in the uptake processes. A strong overlap between the concentric growth rings in the eye lenses and the otolith Sr periodicity was observed, where each consecutive minima in the chemical profile with high accuracy correspond to the width of each lens ring. No comparable trends were seen between growth rings and all other elements measured from both lenses and otoliths. The characteristic rings observed in cod eye lenses do not seem to represent seasonal fluctuation nor are they found to be directly linked to age. With this research, we provide a baseline study identifying elements in corresponding eye lenses and otoliths that show potential for unravelling the environmental and biological conditions experienced by fish.

Impact of gravity on the perception of linear motion.

Accurate perception of gravity and translation is fundamental for balance, navigation, and motor control. Previous studies have reported that perceptual thresholds for earth-vertical (i.e., parallel to gravity) and earth-horizontal (i.e., perpendicular to gravity) translations are equivalent in healthy adults, suggesting that the nervous system compensates for the presence of gravity. However, past study designs were not able to fully separate the effect of gravity from the potential effects of motion direction and body orientation. To quantify the effect of gravity on translation perception relative to these alternative factors, we measured vestibular perceptual thresholds for three motion directions (inter-aural, naso-occipital, and superior-inferior) and three body orientations (upright, supine, and ear-down). In contrast to prior reports, our data suggest that the nervous system does not universally compensate for the effects of gravity during translation, instead, we show that the colinear effect of gravity significantly decreases the sensitivity to stimuli for motions sensed by the utricles (inter-aural and naso-occipital translation), but this effect was not significant for motions sensed by the saccules (superior-inferior translations). We also identified increased thresholds for superior-inferior translation, suggesting decreased sensitivity of motions sensed predominantly by the saccule. An overall effect of body orientation on perception was seen; however, post hoc analyses suggest that this orientation effect may reflect the impact of gravity on self-motion perception. Overall, our data provide fundamental insights into the manner by which the nervous system processes vestibular self-motion cues, showing that the effect of gravity on translation perception is impacted by the direction of motion.NEW & NOTEWORTHY Perception of gravity and translation are fundamental for self-motion perception, balance, and motor control. The central nervous system must accurately disambiguate peripheral otolith signals encoding both linear acceleration and gravity. In contrast to past reports, we show that perception of translation depends on both motion relative to gravity and motion relative to the head. These results provide fundamental insights into otolith-mediated perception and suggest that the nervous system must compensate for the presence of gravity.

Ocean acidification effects on fish hearing.

Humans are rapidly changing the marine environment through a multitude of effects, including increased greenhouse gas emissions resulting in warmer and acidified oceans. Elevated CO2 conditions can cause sensory deficits and altered behaviours in marine organisms, either directly by affecting end organ sensitivity or due to likely alterations in brain chemistry. Previous studies show that auditory-associated behaviours of larval and juvenile fishes can be affected by elevated CO2 (1000 µatm). Here, using auditory evoked potentials (AEP) and micro-computer tomography (microCT) we show that raising juvenile snapper, Chrysophyrs auratus, under predicted future CO2 conditions resulted in significant changes to their hearing ability. Specifically, snapper raised under elevated CO2 conditions had a significant decrease in low frequency (less than 200 Hz) hearing sensitivity. MicroCT demonstrated that these elevated CO2 snapper had sacculus otolith's that were significantly larger and had fluctuating asymmetry, which likely explains the difference in hearing sensitivity. We suggest that elevated CO2 conditions have a dual effect on hearing, directly effecting the sensitivity of the hearing end organs and altering previously described hearing induced behaviours. This is the first time that predicted future CO2 conditions have been empirically linked through modification of auditory anatomy to changes in fish hearing ability. Given the widespread and well-documented impact of elevated CO2 on fish auditory anatomy, predictions of how fish life-history functions dependent on hearing may respond to climate change may need to be reassessed.

Development and evolution of the vestibular apparatuses of the inner ear.

The vertebrate inner ear is a labyrinthine sensory organ responsible for perceiving sound and body motion. While a great deal of research has been invested in understanding the auditory system, a growing body of work has begun to delineate the complex developmental program behind the apparatuses of the inner ear involved with vestibular function. These animal studies have helped identify genes involved in inner ear development and model syndromes known to include vestibular dysfunction, paving the way for generating treatments for people suffering from these disorders. This review will provide an overview of known inner ear anatomy and function and summarize the exciting discoveries behind inner ear development and the evolution of its vestibular apparatuses.

Frequency of vateritic otoliths and potential consequences for marine survival in hatchery-reared Atlantic salmon.

Otoliths are inner-ear structures of all teleost fish with functional importance for hearing and balance. The otoliths usually consist of aragonite, a polymorph of calcium carbonate, but may also take the form partly or entirely of vaterite, a different polymorph of calcium carbonate. Vateritic otoliths occur sporadically in wild fish, but with a higher frequency in hatchery-reared fish. Abnormal otoliths have direct consequences for the inner-ear functions of fish and may be a symptom of environmental stress. In this study, the authors assess the differences in the frequency of abnormal otoliths and degree of abnormality (% vaterite) for different groups of hatchery-reared Atlantic salmon (Salmo salar) smolt and adults. The groups differed in parental broodstock origin (number of generations in hatchery) and treatment temperature. Smolt from the same groups were also released to complete their ocean migration. The otoliths of the returning and recaptured adults were subsequently extracted to assess the difference in frequency and degree of abnormality between the adults and the smolt from corresponding groups. Return rate varied among groups (0.2%-2.6%). The frequency of vateritic otoliths was high (11.4%-64.4%) and differed among smolt groups. The lowest return rates corresponded with the highest frequency of abnormal otoliths for the groups, suggesting that abnormal otoliths may have negative consequences for marine survival. Furthermore, indications of an effect of fast growth on the formation of abnormal otoliths were found for only one of the experimental groups, and for none of the groups after correcting for Type 1 error. This contradicts previous reports, suggesting rapid growth as the main cause of abnormal otoliths. Adult return rates were generally low, but abnormal otoliths were common, with high coverage (% vaterite).

Age, growth and maturity for two highly targeted jack species: Caranx ignobilis and Caranx melampygus.

This study provides growth rate, longevity and maturity estimates for the two important species of jack in Hawai'i: ulua aukea/giant trevally Caranx ignobilis and omilu/bluefin trevally Caranx melampygus. Maximum observed ages for C. ignobilis and C. melampygus were 31 years and 24 years, respectively. Combined sex von Bertalanffy growth parameter values for C. ignobilis and C. melampygus were as follows: L∞  = 1064 mm and K = 0.18 year-1 ; and L∞  = 718 mm and K = 0.20 year-1 , respectively. Female size at maturity was significantly greater than males for both C. ignobilis and C. melampygus. Size and age at maturity for C. ignobilis was 594 mm and 4.4 years for females and 465 mm and 2.8 years for males. Size and age at maturity for C. melampygus was 372 mm and 4.1 years for females and 329 mm and 2.9 years for males. This study provides the first robust demographic data for both of these highly prized and ecologically important predatory species in Hawai'i, which can be used for future assessments or management.

The life history characteristics of Neosebastes pandus and the relationship between sexually dimorphic growth and reproductive strategy among Scorpaeniformes.

Scorpaeniformes are an important component of commercial and recreational fisheries world-wide. The Neosebastes species, found in the western Pacific and south-east Indian Ocean, have received little attention from a research perspective. Samples of the bighead gurnard perch, Neosebastes pandus, collected from the lower west and south coasts of Western Australia, were used to undertake the first comprehensive investigation of the biological characteristics of a Neosebastes species. Opaque zones in sectioned sagittal otoliths were validated as forming annually. Female N. pandus grow to a significantly larger size, on average, than males and dominate the largest size classes, while males, growing to a smaller size, accumulate in the intermediate size classes. Although males were far less numerous than females in those age classes in which both sexes were found, males and females attain similar maximum ages >25 years. Neosebastes pandus spawns over a brief period between May (austral late autumn) and July (austral mid-autumn) when water temperature and day length are declining. The mean monthly gonadosomatic indices (GSI, IGS ) values of females during the spawning period are 37-50 times higher than those of males, which mature at an earlier age and smaller length compared to females. Histological examination of the ovaries of females indicate that their structure is consistent with "general" teleost ovarian anatomy and thus differs from Scorpaena, Helicolenus and Sebastes species whose ovaries are adapted for specialized reproductive modes. The reproductive strategy of N. pandus of maximizing the reproductive output of females, by this sex attaining a larger size than males and pair spawning (i.e., large disparity in IGS values) demonstrates the close lineage between the Neosebastes and other Scorpaeniformes, such as the Scorpaena, Helicolenus and Sebastes.

Age and growth of grey triggerfish Balistes capriscus from trans-Atlantic populations.

Anthropogenic factors that negatively impact reef fishes can include changes in life-history patterns of fisheries-targeted species. Understanding these impacts on growth and population age structure is essential in the management of exploited populations of fishes. This is the first study to directly compare age and growth for a major fisheries species between east and west populations of a transatlantic reef fish. The main goal of this study was to document age and growth in grey triggerfish Balistes capriscus from coastal waters of Ghana in the Gulf of Guinea (GOG) and compare those with the previous growth studies from that region and with the western Atlantic population. A secondary objective of this study was to evaluate the use of otoliths to age triggerfish and to provide a preliminary comparison with spine-derived age estimates. The results obtained from this study provided an updated understanding of the growth and age structure of the eastern B. capriscus population in GOG. The authors documented that shifts in population attributes occurred for B. capriscus after its major decline in abundance. The differences in physical and biotic characteristics of the East and West Atlantic regions and the differences in collection methods of samples make direct comparisons of growth parameters difficult. Nonetheless, overall differences in maximum sizes and ages were apparent; the western Atlantic population had a larger maximum size and older maximum age. The authors also documented that sagittal otoliths can be used to provide age estimates for triggerfish species, and otoliths as an ageing structure had better between-reader precision compared to dorsal spines.

The role of acceleration and jerk in perception of above-threshold surge motion.

Inertial motions may be defined in terms of acceleration and jerk, the time-derivative of acceleration. We investigated the relative contributions of these characteristics to the perceived intensity of motions. Participants were seated on a high-fidelity motion platform, and presented with 25 above-threshold 1 s forward (surge) motions that had acceleration values ranging between 0.5 and 2.5 [Formula: see text] and jerks between 20 and 60 [Formula: see text], in five steps each. Participants performed two tasks: a magnitude estimation task, where they provided subjective ratings of motion intensity for each motion, and a two-interval forced choice task, where they provided judgments on which motion of a pair was more intense, for all possible combinations of the above motion profiles. Analysis of the data shows that responses on both tasks may be explained by a single model, and that this model should include acceleration only. The finding that perceived motion intensity depends on acceleration only appears inconsistent with previous findings. We show that this discrepancy can be explained by considering the frequency content of the motions, and demonstrate that a linear time-invariant systems model of the otoliths and subsequent processing can account for the present data as well as for previous findings.

Bilateral Vestibular Hypofunction in the Time of the Video Head Impulse Test.

OBJECTIVES: Bilateral vestibulopathy is a clinical syndrome in which laboratory testing plays a crucial diagnostic role. We aimed to establish the frequency of detection of that finding in a tertiary level hospital considering the new methods of laboratory vestibular examination nowadays in use, with respect to the conventional caloric and rotatory chair test approaches. DESIGN: Two similar time periods (5 years) were retrospectively evaluated, and the demographic, clinical data and test results from 4,576 patients were reviewed. In the first period, the diagnosis was based on caloric and rotatory chair tests and, in the second, on the video head impulse test. RESULTS: Of the patients included, 3.77% in the first period and 4.58% in the second met the criteria for bilateral vestibular hypofunction; there was no significant difference between both periods. CONCLUSIONS: The functional vestibular evaluation to detect bilateral deficiency makes no significant difference to the number of patients diagnosed with a bilateral vestibulopathy. New diagnostic categories probably depend not only on the availability and accessibility of complete vestibular and visual-vestibular evaluation, but also on recent advances in defining vestibular disorders. Bilateral vestibular hypofunction manifests with very different patterns. Progress in more detailed definition (clinical and laboratory) is needed, in particular when all 6 semicircular canals and both maculae are available for testing.

Bioaccumulation of mining derived metals in blood, liver, muscle and otoliths of two Arctic predatory fish species (Gadus ogac and Myoxocephalus scorpius).

Mining activities can cause adverse and long-lasting environmental impacts and detailed monitoring is therefore essential to assess the pollution status of mining impacted areas. Here we evaluated the efficacy of two predatory fish species (Gadus ogac i.e. Greenland cod and Myoxocephalus scorpius i.e. shorthorn sculpin) as biomonitors of mining derived metals (Pb, Zn, Cd and Hg) by measuring concentrations in blood, liver, muscle and otoliths along a distance gradient near the former Black Angel Pb-Zn mine (West Greenland). We detected metals in all tissues (except Cd and Hg in otoliths) and sculpin generally displayed higher concentrations than cod. For both species, concentrations were generally highest closest to the dominant pollution source(s) and gradually decreased away from the mine. The clearest gradient was observed for Pb in blood and liver (both species), and for Pb in otoliths (sculpin only). Similar to dissolved concentrations in seawater (but in contrast to bottom sediment), no significant decrease was found for Zn, Cd and Hg in any of the tissues. This demonstrates that by including tissues of blood (representing recent accumulation) and otolith (representing more long-term exposure signals) in the sampling collection, the temporal information on contaminant exposure and accumulation can be extended. We therefore conclude that both fish species are suitable as biomonitors near Arctic mine sites and, moreover, that blood and otoliths can serve as important supplementary monitoring tissues (in addition to liver and muscle traditionally sampled) as they provide extended temporal information on recent to long-term contaminant exposure.

Larval parasitic copepods affect early life history traits of a temperate clingfish.

Larval copepods are frequent parasites that infest fish larvae along the Chilean coast. Because these parasites develop on fish during the early development, when their bodies are fragile and in a recent stage, they can affect the fishes' early life history traits (ELHT). The goal of this study was to determine the effect of parasitic copepods on the ELHT of the larvae of the clingfish Gobiesox marmoratus (Teleostei: Gobiesocidae) using otolith microstructure analysis. Ichthyoplankton samples were collected during austral winter (July and August 2012), in the inner shelf waters off Valparaiso Bay, central Chile. A total of 95 non-parasitized larvae (NPL) and 95 parasitized (PL) with copepods were randomly selected for subsequent analyses. Parasitized larvae of G. marmoratus were larger than NPL. The right otolith tended to be larger than the left otolith in the fish larvae, but with a higher asymmetry in PL. The PL showed larger otoliths-at-size than the NPL, particularly in smaller larvae (< 8 mm of standard length, SL). Nonetheless, parasitized larvae larger than 8 mm SL showed the opposite trend that is smaller-at-size otoliths than NPL. The Gompertz models indicated that the asymptotic length of NPL doubled the length of PL; this suggests that parasitic copepods affect the maximum size attained by the PL. In conclusion, parasitic copepods negatively affect the ELHT of G. marmoratus larvae and the greater asymmetry can be attributed to parasitism.