Otolith Microstructure Analysis Research Articles

Impact of the Great East Japan Earthquake tsunami on growth and survival of Pacific cod (Gadus macrocephalus)

A massive tsunami hit the north Pacific coast of Japan on 11 March 2011. We evaluated the effects of the tsunami on the distribution, growth, and survival of young Pacific cod (Gadus macrocephalus) using data from benthic trawl surveys and otolith microstructure analysis. The distribution of Pacific cod juveniles differed between 2011 and 2008–2010. The 2011 year class was smaller in body size than those in 2008–2010. The majority of 2011 year-class juveniles was captured in deeper areas at a smaller body size, whereas those of previous year classes were primarily distributed in shallower water. The peak hatch of the 2011 year-class juveniles was from early to late February, which was several days later than those of the 2008 and 2010 year classes. The 2011 year class grew at the same rate as those from 2008 and 2010 until the day of the tsunami, but had a lower growth rate during the 30 days after the tsunami, resulting in a decrease in fish size at settlement. Growth of the 2011 year class was also inferior soon after the day of the tsunami in almost all groups divided by the hatching period. Growth of juveniles captured in shallower water following the tsunami in 2011 tended to be slower than that of juveniles captured in deeper water. Our results suggest that the tsunami caused a decrease in growth rates for approximately 30 days and a change in the distribution of juvenile fish relative to prior years. The change in distribution was primarily the result of mortality in shallow water caused by physical damage and (or) subsequent decreased growth. Considering these results and the finding that the recruitment level and the recruits per spawning in the 2011 year class were low, the tsunami may have affected the determination of the recruitment level.

Interannual variation in the larval development of a coral reef fish in response to temperature and associated environmental factors

Climate change is predicted to increase ocean temperatures and influence weather patterns. Here, we examine the influence of temperature and other environmental variables on key early life traits of the coral reef damselfish, Pomacentrus moluccensis, based on ten cohorts of newly settled fish collected over 13 years from around Lizard Island (Great Barrier Reef, Australia). Pelagic larval duration (PLD), larval growth and size at settlement were estimated through otolith microstructure analysis. Multiple regression techniques were used to measure the strength of the associations between these traits and developmental temperature, rain, wind speed and solar radiation. Temperature accounted for 18.4, 26.7 and 25.0 % of the variability in PLD, growth rates and settlement size, respectively. PLDs generally declined and growth rates generally increased with increasing temperatures to ~28 °C, above which PLDs tended to increase and growth rates tended to decrease. Size at settlement did not differ between ~25 and ~28 °C, but tended to decrease with increasing temperature above ~28 °C. Together rain, wind speed and solar radiation explained 6.3, 26.3 and 33.7 % of the remaining variability in PLD, growth rates and size at settlement, respectively. Higher wind speeds were generally associated with longer PLDs. Increasing wind, high rainfall and increasing solar radiation were associated with slower growth rates and smaller sizes at settlement. Overall, results suggest that ~28 °C is likely to be a thermal optimum for larval development for this species and other environmental factors associated with climate change including rainfall, wind speed and solar radiation should be considered in predictions of effects on larval fish.

Interannual variations in the hatching pattern, larval growth and otolith size of a sand-dwelling fish from central Chile

The interannual variation (2010–2013) of larval abundance, growth and hatching patterns of the Chilean sand stargazer Sindoscopus australis (Pisces: Dactyloscopidae) was investigated through otolith microstructure analysis from samples collected nearshore (<500 m from shore) during austral late winter-early spring off El Quisco bay, central Chile. In the studied period, the abundance of larval stages in the plankton samples varied from 2.2 to 259.3 ind. 1000 m−3; larval abundance was similar between 2010 and 2011, and between 2012 and 2013, but increased significantly from 2011 to 2012. The estimated growth rates increased twice, from 0.09 to 0.21 mm day−1, between 2011 and 2013. Additionally, otolith size (radius, perimeter and area), related to body length of larvae, significantly decreased from 2010 to 2012, but increases significantly in 2013. Although the mean values of microincrement widths of sagitta otoliths were similar between 2010 and 2011 (around 0.6–0.7 μm), the interindividual variability increases in 2011 and 2013, suggesting large environmental variability experienced by larvae during these years. Finally, the hatching pattern of S. australis changed significantly from semi-lunar to lunar cycle after 2012.

Combining otolith microstructure and trace elemental analyses to infer the arrival of juvenile Pacific bluefin tuna in the California current ecosystem

Abstract Juvenile Pacific bluefin tuna (PBT, Thunnus orientalis) are known to migrate from western Pacific spawning grounds to their eastern Pacific nursery and feeding grounds in the California Current Large Marine Ecosystem (CCLME), but the timing, durations, and fraction of the population that makes these migrations need to be better understood for improved management. To complement recent work focused on stable isotope and radiotracer approaches (“tracer toolbox”; Madigan et al., 2014) we explored the suitability of combining longitudinal analyses of otolith microstructure and trace elemental composition in age ∼1–2 PBT (n = 24, 66–76 cm curved fork length) for inferring the arrival of individuals in the CCLME. Element:Ca ratios in transverse otolith sections (9–12 rows, triplicate ablations from primordium to edge, ø50 μm) were quantified for eight elements: Li, Mg, Mn, Co, Cu, Zn, Sr, and Ba, which was followed by microstructure analysis to provide age estimates corresponding to each ablation spot. Age estimates from otoliths ranged from 328 to 498 d post-hatch. The combined elemental signatures of four elements (Ba, Mg, Co, Cu) showed a significant increase at the otolith edge in approximately half of the individuals (30–60 d before catch). Given the different oceanographic properties of oligotrophic open Pacific vs. high nutrient, upwelling CCLME waters, this signal is consistent with the entry of the fish into the CCLME, which was estimated to occur primarily in July after a transoceanic migration of ∼1.5–2.0 months. Our approach comprises a useful addition to the available tracer toolbox and can provide additional and complementary understanding of trans-Pacific migration patterns in PBT.

Larval and juvenile growth of chub mackerel Scomber japonicus in relation to recruitment in the western North Pacific

To detect indices of recruitment intensity of the Pacific stock of chub mackerel Scomber japonicus, the relationship between the growth rate during early life and recruitment variability and the effects of temperature on annual change of the growth rate were examined. Growth-trajectories in larval and juvenile stages were back-calculated by otolith microstructure analysis using juveniles collected in the Kuroshio–Oyashio transition region of the western North Pacific in May and June from 2002 to 2011. A total of 532 otoliths were analysed. Hatch dates were distributed from mid-March to mid-May and most chub mackerel hatched in April. Mean daily growth rates ± standard deviation (SD) of the April cohort in larval and juvenile stages ranged between 1.03 ±0.10 (2006) and 1.52 ±0.23 mm day−1 (2009). The mean daily growth rate and larval stage duration were significantly related to recruitment which had been estimated by virtual population analysis. The results indicated the growth rate of the April cohort was an important index of year-class strength. There was a significant correlation between sea surface temperature experienced by each fish and the mean daily growth rate during the larval period. Higher water temperature led to faster growth and shorter larval stage duration of the April cohort of the Pacific stock of chub mackerel.

Larval fish feeding ecology, growth and mortality from two basins with contrasting environmental conditions of an inner sea of northern Patagonia, Chile

During austral spring 2011, a survey was carried out in the inland sea (41°30′–44°S) of north Patagonia, South Pacific, studying a northern basin (NB: Reloncaví Fjord, Reloncaví Sound and Ancud Gulf) characterized by estuarine regime with stronger vertical stratification and warmer (11–14 °C) and most productive waters, and a southern basin (SB: Corcovado Gulf and Guafo mouth), with more oceanic water influence, showed mixed conditions of the water column, colder (11–10.5 °C) and less productive waters. Otolith microstructure and gut content analysis of larval lightfish Maurolicus parvipinnis and rockfish Sebastes oculatus were studied. Larval M. parvipinnis showed similar growth rates in both regions (0.13–0.15 mm d−1), but in NB larvae were larger-at-age than in SB. Larval S. oculatus showed no differences in size-at-age and larval growth (0.16 and 0.11 mm d−1 for NB and SB, respectively). M. parvipinnis larvae from NB had larger number of prey items (mostly invertebrate eggs), similar total volume in their guts and smaller prey size than larvae collected in SB (mainly calanoid copepods). Larval S. oculatus had similar number, volume and body width of prey ingested at both basins, although prey ingestion rate by size was 5 times larger in NB than in SB, and prey composition varied from nauplii in NB to copepodites in SB. This study provides evidence that physical–biological interactions during larval stages of marine fishes from Chilean Patagonia are species-specific, and that in some cases large size-at-age correspond to increasing foraging success.

Early life stages of plaice Pleuronectes platessa in cold-water nurseries

Event Abstract Back to Event Early life stages of plaice Pleuronectes platessa in cold-water nurseries Filipe Martinho1*, Vânia Freitas2, 3, Paulo T. Santos4, Camila Bremm4, Joana Campos2, 3 and Henk W. Van Der Veer2 1 Centre for Functional Ecology - CFE, Department of Life Sciences, Portugal 2 NIOZ - Royal Netherlands Institute for Sea Research, Netherlands 3 CIIMAR – Interdisciplinary Centre of Marine and Environmental Research, Portugal 4 FCUP – Faculdade de Ciências da Universidade do Porto, Portugal Plaice Pleuronectes platessa (Linnaeus, 1758) is one of the most important commercial flatfish in the European continent, whose captures have reduced considerably in recent decades due to the high pressure of fisheries. Despite the wide distribution of this species, most studies have focused on the North Sea, its central area of occurrence, and very little information is available concerning the populations living at the northern limit of its distribution. Age determination is essential to study population dynamics of commercially important species such as plaice, and can be inferred through otolith microstructure analysis. The aim of this work was to investigate the timing of early life events (spawning, larval, metamorphosis and settlement stage duration) and growth of juvenile plaice in two cold-water nursery areas in northern Norway (Valosen estuary and Storfjord). A latitudinal cline was observed in the main life-history events, such as spawning, and the onset of larval and metamorphosis stages. Settlement to benthic habitats (which coincides with metamorphosis) was estimated to have occurred between mid-May and early-September (peak from the end May and mid July) in the Valosen, and between the end of May and early July (peak in June) in the Storfjord. In the Storfjord area, larval and metamorphosis stage duration seemed to be shorter, probably due to a reduced window of opportunity for growth and survival at the northernmost extremes. Size at settlement was negatively related with hatch day, implying that the older larvae were larger at settlement, a consequence of higher fecundity of females earlier in the spawning season. A significant relationship between size at settlement and total length reinforced this evidence. The results demonstrate the influence of latitude in the early life stages of plaice, mainly by the regulatory effect of temperature in the growth and survival of larvae and juveniles. Acknowledgements This study was funded by the Portuguese Foundation for Science and Technology, through the following grants, with funds from the European Social Fund and the Portuguese Operational Human Potential Program (POPH): F Martinho - Investigador FCT programme IF/01410/2012 V Freitas - Post doc grant SFRH/BPD/75858/2011 J Campos - Post doc grant SFRH/BPD/71205/2010 Keywords: latitudinal gradient, Plaice, otolith microstructure, Nursery grounds, Norway Conference: XV European Congress of Ichthyology, Porto, Portugal, 7 Sep - 11 Sep, 2015. Presentation Type: Oral Presentation Topic: Otoliths as a tool to study fish life cycles Citation: Martinho F, Freitas V, Santos PT, Bremm C, Campos J and Van Der Veer HW (2015). Early life stages of plaice Pleuronectes platessa in cold-water nurseries. Front. Mar. Sci. Conference Abstract: XV European Congress of Ichthyology. doi: 10.3389/conf.fmars.2015.03.00090 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 18 Nov 2015; Published Online: 19 Nov 2015. * Correspondence: Dr. Filipe Martinho, Centre for Functional Ecology - CFE, Department of Life Sciences, Coimbra, 3000-456, Portugal, fmartinho@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Filipe Martinho Vânia Freitas Paulo T Santos Camila Bremm Joana Campos Henk W Van Der Veer Google Filipe Martinho Vânia Freitas Paulo T Santos Camila Bremm Joana Campos Henk W Van Der Veer Google Scholar Filipe Martinho Vânia Freitas Paulo T Santos Camila Bremm Joana Campos Henk W Van Der Veer PubMed Filipe Martinho Vânia Freitas Paulo T Santos Camila Bremm Joana Campos Henk W Van Der Veer Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Impact of environmental factors on recruitment and hatching patterns of Horse Mackerel (L.) collected in a nearshore rocky reef system

Event Abstract Back to Event Impact of environmental factors on recruitment and hatching patterns of Horse Mackerel (L.) collected in a nearshore rocky reef system Maria Klein1, 2*, Elisabeth Van Beveren1, 3, Diana Rodrigues2, Emanuel J. Gonçalves2, Ester A. Serrão1 and Rita Borges1, 2 1 Centre of Marine Sciences, Portugal 2 MARE - Marine and Environmental Sciences Centre, ISPA – Instituto Universitário, Portugal 3 IFREMER (Institut Français de Recherche pour l’Exploitation de la MER), CRH, Research Unit EME (UMR 212), France Horse mackerel (Trachurus trachurus, Linnaeus, 1758) is a highly exploited fish species, common throughout the North-East Atlantic. As a pelagic-neritic fish it typically occurs over the shelf at 100-200 m depth on sandy bottom and most research has focused on adults or early life stages (eggs and larvae), caught or examined in deeper waters. Nevertheless, larvae and early stages of Trachurus species have been observed in the nearshore environment of a rocky reef system in Portugal. More research is needed in order to understand the importance of nearshore environments for horse mackerel. In addition little is known on how environmental processes might affect early life parameters of this species. In this study we monitored the arrival of early juvenile horse mackerel to the reef environment at a fine time scale, and analyzed the relationship of environmental factors with patterns of recruitment and hatching, revealed by otolith microstructure analysis. In total around 2500 fish were collected with Standard Monitoring Units for the Recruitment of Fish (SMURF) and a distinct depth preference was recorded as 99% of fish were sampled with surface SMURFs. A GAM and GAMM analysis of the recruitment and hatching pattern, respectively, revealed a strong relationship with the lunar cycle and local up-welling. Both recruitment and hatching had a periodic pattern with peaks near the new moon; upwelling had a negative impact. Further, the study indicated that the nearshore environment might be an important nursery area for the post-larval growth of horse mackerel. Keywords: Trachurus trachurus, Lunar pattern, upwelling, juvenile, cohort, generalized additive models Conference: XV European Congress of Ichthyology, Porto, Portugal, 7 Sep - 11 Sep, 2015. Presentation Type: Oral Presentation Topic: Otoliths as a tool to study fish life cycles Citation: Klein M, Van Beveren E, Rodrigues D, Gonçalves EJ, Serrão EA and Borges R (2015). Impact of environmental factors on recruitment and hatching patterns of Horse Mackerel (L.) collected in a nearshore rocky reef system. Front. Mar. Sci. Conference Abstract: XV European Congress of Ichthyology. doi: 10.3389/conf.fmars.2015.03.00066 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 11 Nov 2015; Published Online: 11 Nov 2015. * Correspondence: Ms. Maria Klein, Centre of Marine Sciences, Faro, 8005-139, Portugal, mariaklein55@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Maria Klein Elisabeth Van Beveren Diana Rodrigues Emanuel J Gonçalves Ester A Serrão Rita Borges Google Maria Klein Elisabeth Van Beveren Diana Rodrigues Emanuel J Gonçalves Ester A Serrão Rita Borges Google Scholar Maria Klein Elisabeth Van Beveren Diana Rodrigues Emanuel J Gonçalves Ester A Serrão Rita Borges PubMed Maria Klein Elisabeth Van Beveren Diana Rodrigues Emanuel J Gonçalves Ester A Serrão Rita Borges Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Close encounters with eddies: oceanographic features increase growth of larval reef fishes during their journey to the reef.

Like most benthic marine organisms, coral reef fishes produce larvae that traverse open ocean waters before settling and metamorphosing into juveniles. Where larvae are transported and how they survive is a central question in marine and fisheries ecology. While there is increasing success in modelling potential larval trajectories, our knowledge of the physical and biological processes contributing to larval survivorship during dispersal remains relatively poor. Mesoscale eddies (MEs) are ubiquitous throughout the world's oceans and their propagation is often accompanied by upwelling and increased productivity. Enhanced production suggests that eddies may serve as important habitat for the larval stages of marine organisms, yet there is a lack of empirical data on the growth rates of larvae associated with these eddies. During three cruises in the Straits of Florida, we sampled larval fishes inside and outside five cyclonic MEs. Otolith microstructure analysis revealed that four of five species of reef fish examined had consistently faster growth inside these eddies. Because increased larval growth often leads to higher survivorship, larvae that encounter MEs during transit are more likely to contribute to reef populations. Successful dispersal in oligotrophic waters may rely on larval encounter with such oceanographic features.

Age estimation of juvenile European hake Merluccius merluccius based on otolith microstructure analysis: a slow or fast growth pattern?

The main goal of this study was to examine otolith microstructure and to estimate the age and growth of European hake Merluccius merluccius from the eastern Mediterranean Sea. One hundred and twenty-nine specimens ranging from 102 to 438 mm in total length (LT ) were used. Age estimations were based on the study of the otolith microstructure, which was revealed after grinding both frontal sides of otoliths. The enumerations of the daily growth increments (DGI) as well as their width (WDGI ) measurements were made on calibrated digital images. The number of DGI in otoliths ranged between 163 and 717. Four phases in the WDGI evolution were distinguished: (1) larval-juvenile pelagic phase, with an increasing trend in WDGI up to the 60th DGI, (2) settlement phase, with a short-term deceleration in WDGI between the 61st and 150th DGI, (3) juvenile demersal phase, characterized by a stabilization of WDGI from 151st to 400th DGI and (4) adult phase, with a decreasing trend in WDGI after the 400th DGI. Age, sex and month of formation were found to affect the WDGI in all phases, with the exception of age at the juvenile demersal phase. The power curve with intercept model described best the relationship of M. merluccius LT with age (TDGI ), according to Akaike criteria, revealing differences in growth between females [LT = 65 · 36(TDGI )(0 · 40) - 388 · 55] and males [LT = 69 · 32(TDGI )(0 · 37) - 352 · 88] for the sizes examined. The mean daily growth rates were 0·61 mm day(-1) for females and 0·52 mm day(-1) for males, resulting in an LT of 283 and 265 mm at the end of their first year of life. In comparison with previous studies on the Mediterranean Sea, the results of this study showed a greater growth rate, similar to results from tagging experiments and otolith microstructure analyses for M. merluccius in other geographic areas.

Daily otolith growth and ontogenetic geochemical signatures of age-0 anchovy (Engraulis encrasicolus) in the Gulf of Cádiz (SW Spain).

The European anchovy fishery in the Gulf of Cádiz (ICES Division IXa South) is largely influenced by age-0 individuals. Knowledge of young of the year growth dynamics is crucial for management, yet data on daily growth are lacking in the area. Linking growth patterns to the environment requires information on habitat occupancy through ontogeny of the fish that reach the fishery, as anchovy use different areas of the Gulf and the Guadalquivir Estuary through development. We describe the growth dynamics of age-0 anchovy through otolith microstructure analysis, and couple these data with data on microchemical signals in the otoliths to shed light into habitat use and growth dynamics in the area. Age-0 anchovy captured in September, 2011 in the Gulf ranged from 3 to 6 months old for similar sizes, with average growth rates varying twofold. Individual non-linear growth curves showed that maximum otolith growth was positively correlated with the date of spawning, which in turn was negatively correlated with the time to reach maximum growth. There was no correlation between growth parameters and body length or condition (Fulton K) at capture. The strontium:calcium (Sr/Ca) and magnesium:calcium (Mg/Ca) ratios were significantly lower at the edge of the otolith (approximately the age of capture) than at ages corresponding to larval and early juveniles (&lt;60 days old), but values fell within typical estuarine-dwelling species. The barium:calcium ratio (Ba/Ca) increased significantly in the edge of the otolith, which possibly resulted from residency in highly productive coastal waters or from ontogenetic effects. The variance in otolith elemental ratios was larger at otolith back-calculated ages around 50 days old, age which coincides with the presumed closer dependence of estuarine waters. Our data are a first step towards understanding the contribution of the estuarine system to the fishery of anchovy in the Gulf. The limitations of the approach and future steps are discussed.

Larval growth of two species of lanternfish at nearshore waters from an upwelling zone based on otolith microstructure analyses

Summary Larval growth and hatching days of lanternfishes Diogenichthys laternatus and Myctophum nitidulum (Myctophidae) collected in September 2012 in nearshore waters (<1 km offshore) at Mejillones Bay, northern Chile, were estimated on the basis of microstructure analyses of sagitta otoliths, to establish potential differences in early traits of both species from the productive coastal waters of the Humboldt Ecosystem. Growth increments were well defined, and no accessory primordia were observed in the analyses of the largest individuals in either species (8.61 and 9.17 mm BL, respectively). Both larval species displayed slow and similar growth rates: 0.057 ± 0.016 mm day−1 for D. laternatus, and 0.061 ± 0.005 mm day−1 for M. nitidulum. A large variability in the size-at-age in larvae of both species was detected. However, a recent otolith growth index showed all M. nitidulum in similar condition 5 days before capture, but with three D. laternatus in better condition and only one in a poorer condition than the other D. laternatus individuals. Growth trajectories estimated by the microincrement width of sagitta otoliths, indicated the presence of fast- and slow-growing larvae for both species. Also, the back-calculated ‘birth’ days suggest a large hatching pulse for D. laternatus near the third-quarter moon. The small sampling size of M. nitidulum precluded a robust conclusion on hatching patterns, although most individuals were hatched between the third quarter and the new moon. It is suggested that the slow growth rates estimated for both larval species might be caused by cold waters from upwelling events and/or allometric growth during early development of these lanternfish.

Disentangling the effects of inherent otolith growth and model-simulated ecosystem parameters on the daily growth rate of young anchovies

Otolith increment widths have often been used to infer somatic growth history when studying the influence of temperature and food supply. However, there is no functional relation- ship between otolith accretion rate ('inherent otolith growth') and somatic growth rate; although both may be mediated by temperature and food, the uncoupling of these rates under changing environmental conditions or during ontogenetic transitions can undermine the sensitivity of incre- ment width analyses. We used otolith microstructure analysis to model the daily growth of anchovy Engraulis encrasicolus juveniles collected from the North Aegean Sea in July 2007, December 2007 and February 2009. To assess the environmental causes of seasonal variability in growth we used daily outputs of environmental variables from a coupled 3D hydrodynamic-bio- geochemical model (POM-ERSEM) as a proxy for the potential environment that fish experienced during their development. According to the simulation, juveniles that hatched in late autumn- winter developed in unfavorable conditions (low temperature, low productivity); however, they exhibited wider otolith increments before metamorphosis. To specifically study environmental influences on the daily growth rates, we used the simulated environmental variables in gener- alised additive model (GAM) analysis of otolith increment widths, while also taking into con - sideration inherent otolith growth, expressed by the explanatory variables 'previous increment width' and 'age'. The inclusion of the interaction term 'age' × 'sampling period', rather than 'age', accounted for the seasonal effects on ontogenetic changes (timing and duration of metamorphosis) and the differences in growth-selective mortality among samples. Results showed that the daily growth rate of anchovy is influenced by temperature, exhibiting an optimum at 24.5°C, and increases significantly with increased mesozooplankton concentration (i.e. food availability). The analysis highlights that, in order to infer the daily somatic growth from fish otolith increment data and understand the environmental influences, inherent otolith growth has to be disentangled and otolith width trajectories standardised for between-sample differences in ontogenetic changes and growth selective mortality.

Comparing early life traits of hakes from Chilean Patagonian fjords inferred by otolith microstructure analysis

Comparison of larval growth and back-calculated hatch dates on the basis of microstructure analysis of sagitta otoliths were carried out in wild-caught larvae of three commercially important gadiform fishes from Northern Patagonia, South Pacific, Chilean hake Merluccius gayi, southern hake Merluccius australis, and Patagonian grenadier Macruronus magellanicus. Because of the morphological similarities in their larval stages, we hypothesize that early life traits (ELT) will be different among the hake species in order to avoid/reduce interspecific competition. During October–November 2011, there was differences in the spatial distribution of the surviving larvae from the three species along the inner sea; while larval Chilean hake were concentrated in the warmer and fresher seawaters of the Reloncaví fjord, larval Patagonian grenadier were aggregated southward, in the Ancud Gulf, while larval southern hake were found throughout the area, but in low density. Temporal differences were evident in the back-calculated hatch days among species; larval hakes of genus Merluccius hatched during late October, while larval grenadier hatched between August and September. Estimated larval growth rates differed among hake species; larval M. magellanicus experienced the fastest growth rates (0.334±0.01mmd−1), while larval M. australis experienced growth rates of 0.220±0.01mmd−1, and larval M. gayi showed the slowest growth rates (0.180±0.01mmd−1). Therefore, resource partitioning both in time and space are occurring among early life stages of M. gayi, M. australis and M. magellanicus during austral spring season in Northern Patagonian fjords of Chile.

Characteristics of juvenile survivors reveal spatio-temporal differences in early life stage survival of Baltic cod

The spatio-temporal origin of surviving juvenile Baltic cod Gadus morhua was investigated by coupling age information from otolith microstructure analysis and hydrodynamic modeling, which allowed backtracking of drift routes in time and space. The suitability of hydrodynamic modeling for drift simulations of early life stages of Baltic cod up to the pelagic juvenile stage was validated by comparing model simulations with the catch distribution from a survey targeting pelagic juveniles, and mortality rates and hatch date distributions of pelagic and demersal juveniles were estimated. Hatch dates and hatch locations of juvenile survivors showed distinct patterns which did not agree well with the abundance and spatial distribution of eggs, suggesting marked spatio-temporal differences in larval survival. The good agreement of the spatio-temporal origin of survivors from this field investigation with previous modeling studies on the survival chances of early-stage larvae and with general spatio-temporal patterns of larval prey availability suggests that differences in survival are related to food availability during the early larval stage. Results are discussed in relation to the recruitment process of Baltic cod, in particular with respect to the critical period and match-mismatch hypotheses, and to possible implications for the placement of a Marine Protected Area which was established to ensure undisturbed spawning of Baltic cod.

Daily growth rates and hatch date distributions of common two-banded seabream, Diplodus vulgaris inhabiting the Çanakkale shallow waters of Turkey

Otolith microstructure analysis was used to determine daily age, growth rate and hatching periods of young of the year (YOY) common two-banded seabream, Diplodus vulgaris, collected at two sites by using beach seine from Çanakkale shallow waters between January and December 2007. Total length of the YOY D. vulgaris was between 12 and 86 mm and the daily ages ranged between 42 and 313 days. Somatic growth rate estimated by fitting a linear regression to the age–length data set was calculated as 0.273 mm day−1. According to the length–age regression analysis, maximum daily growth rates were found 0.277 mm day−1 in the lowest sea temperature period and minimum values of 0.274 mm day−1 were observed in the declining sea temperature period. Analysis of covariance indicated that there were no significant differences in the linear growth equations for the two cohorts (F = 0.4008, P = 0.527). Hatching period of the YOY was estimated to occur between October and March with relatively higher frequency in January. This study has shown that YOY D. vulgaris is a winter spawner in the Çanakkale shallow waters.

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.

A semi-automated method for daily age estimation in larval populations by discriminant function models

Discriminant analysis including the best age-correlated variables selected by SMLR's to construct a predictive model based on somatic and otolith biometry was applied. Age of anchovy larvae ranging from 10 to 12mm collected along Western Mediterranean coasts during MEDIAS209 survey were estimated by otolith microstructure analysis and compared with the number of daily increments estimated by the model. The model compound by Perimeter2+Area2 was able to estimate correctly the age of the otoliths in 75% of the cases assuming ±1 day of error increasing to 90% assuming ±2 days of error with mean values of APE (3.33%) and CV (4.71%) systematically low. The results indicate the precision of the increment estimates. Moreover, no differences between the estimated ages from direct readings and those estimated by the model were observed. The proposed method implies a reduction in the subjectivity factor and the cost/benefit ratio for ageing studies in fish larvae.

Growth and hatching of annular seabream, Diplodus annularis, from Turkey determined from otolith microstructure

Otolith microstructure analysis was used to determine daily growth rate and hatching periods of young of the year (YOY) annular seabream, Diplodus annularis, collected by using beach seine from Çanakkale shallow waters between January and December 2007. Total length of the YOY D. annularis was between 20 and 85 mm and the daily ages ranged between 27 and 205 d. Somatic growth rate, estimated by fitting a linear regression to the age–length data set, was calculated as 0.369 mm d−1. Seasonal changes in the growth rate of the YOY D. annularis have been found to be 0.381, 0.369, 0.357 and 0.308 mm d−1 for individuals that hatched in spring, summer, autumn and winter, respectively. Analysis of covariance indicated that there were no significant differences (P &gt; 0.05) in the growth rates between the seasons. Hatching period of the YOY D. annularis was estimated to occur between March and September, with relatively higher hatching frequency in June.

Growth, mortality and hatch-date distributions of striped sea bream Lithognathus mormyrus inhabiting the Çanakkale Strait, Turkey

This paper studies age, growth and hatch date distributions of young of the year striped sea bream Lithognathus mormyrus from Canakkale near shores by using a beach seine during September 2006–December 2007. Using otolith microstructure analysis, a total of 416 specimens ranging from 20 to 103 mm LT were aged and found to be between 30 and 307 days old. Average growth rates were estimated to 0.325 mm d−1. The juvenile instantaneous mortality coefficient was found to be 0.0219, which corresponds to a daily mortality of 2.16%. The hatching period of the striped sea bream was determined to occur between April and January, with relatively higher hatching frequency in August.