Historical changes in juvenile southern bluefin tuna Thunnus maccoyii growth rates based on otolith measurements

Suspected historic changes in juvenile southern bluefin tuna Thunnus maccoyii growth rates were investigated using otolith increment width data. Four hundred and ninety otoliths were selected from fish estimated to be between 1 and 41 years-old. The distance between the first five annuli were measured on the otoliths, giving estimates of otolith growth for age classes 1+ to 4+ years for fish spawned from the early 1960s to mid 1990s. The data showed that growth rates of juveniles (age 1+ and 2+ years) started to increase at around 1979–1980, and that growth continued to increase throughout the 1980s and early 1990s. Lee's phenomenon was not observed in the data. Correlation tests did not reveal clear relationships between annual otolith growth and regional environmental variables such as sea surface temperature or Southern Oscillation Index. The increase in otolith growth, however, was consistent with juvenile growth estimates obtained from other sources, and correlated with large-scale trends in population size and environmental conditions.     

Predicting human walking gaits with a simple planar model

Models of human walking with moderate complexity have the potential to accurately capture both joint kinematics and whole body energetics, thereby offering more simultaneous information than very simple models and less computational cost than very complex models. This work examines four- and six-link planar biped models with knees and rigid circular feet. The two differ in that the six-link model includes ankle joints. Stable periodic walking gaits are generated for both models using a hybrid zero dynamics-based control approach. To establish a baseline of how well the models can approximate normal human walking, gaits were optimized to match experimental human walking data, ranging in speed from very slow to very fast. The six-link model well matched the experimental step length, speed, and mean absolute power, while the four-link model did not, indicating that ankle work is a critical element in human walking models of this type. Beyond simply matching human data, the six-link model can be used in an optimization framework to predict normal human walking using a torque-squared objective function. The model well predicted experimental step length, joint motions, and mean absolute power over the full range of speeds.     

Application of otolith mass and shape for discriminating scabbardfishes Aphanopus spp. in the north‐eastern Atlantic Ocean

The otolith was used to investigate the variability between Aphanopus carbo and Aphanopus intermedius inhabiting the north‐eastern Atlantic Ocean. The results indicate a high degree of morphological affinity between species and areas; a noticeable metabolic change in the otolith shape was noted in the specimens of A. carbo, which may be related to migrations of individuals from shallow water (closer to the continental coast) to deeper water (archipelagos of Madeira and the Canary Islands). The results suggest a single population for both species in the north‐eastern Atlantic Ocean, although not conclusively.     

Partial migration: growth varies between resident and migratory fish

Partial migration occurs in many taxa and ecosystems and may confer survival benefits. Here, we use otolith chemistry data to determine whether fish from a large estuarine system were resident or migratory, and then examine whether contingents display differences in modelled growth based on changes in width of otolith growth increments. Sixty-three per cent of fish were resident based on Ba : Ca of otoliths, with the remainder categorized as migratory, with both contingents distributed across most age/size classes and both sexes, suggesting population-level bet hedging. Migrant fish were in slightly better condition than resident fish based on Fulton''s K condition index. Migration type (resident versus migratory) was 56 times more likely to explain variation in growth than a model just incorporating year- and age-related growth trends. While average growth only varied slightly between resident and migratory fish, year-to-year variation was significant. Such dynamism in growth rates likely drives persistence of both life-history types. The complex relationships in growth between contingents suggest that management of species exhibiting partial migration is challenging, especially in a world subject to a changing climate.     

Diverse migratory histories of Japanese Trachidermus and Cottus species (Cottidae) as inferred from otolith microchemistry

The migratory histories of Japanese freshwater sculpins, one Trachidermus and four Cottus species, were studied by examining strontium (Sr) and calcium (Ca) concentrations in their otoliths using wavelength dispersive X‐ray spectrometry on an electron microprobe. The Sr : Ca ratios in the otoliths changed with salinity of the habitat. The otoliths of Cottus nozawae showed consistently low Sr : Ca ratios, with an average of 3·37 × 10^?3 from the core to the edge, suggesting a freshwater resident life cycle. In contrast, the otolith Sr : Ca ratios for Trachidermus fasciatus and Cottus kazika changed along the life history transects possibly in accordance with their migration patterns from sea to fresh water. The ratios of T. fasciatus and C. kazika averaged 5·4 × 10^?3 and 5·3 × 10^?3 respectively, in the otolith region from the core to the points 450–890 μm, and changed to the lower levels, averaging 2·0 × 10^?3 and 2·7 × 10^?3, in the outer otolith region. These data suggest that both the species have a catadromous life cycle. The otoliths of Cottus hangiongensis had low Sr : Ca ratios in the two regions from the core to the points 15–30 μm and the points 415–582 μm to the edge, averaging 2·0 × 10^?3 and 1·9 × 10^?3, with significantly higher ratios in the narrow area between these regions, averaging 4·6 × 10^?3. Similar ontogenetic changes in otolith Sr : Ca ratios were found in the otoliths of Cottus amblystomopsis, suggesting their amphidromous life cycle. These findings suggest that otolith Sr : Ca ratios reflect individual life histories and that Japanese Trachidermus and Cottus species have diverse migratory histories.     

Seasonal variability in growth of larval Japanese anchovy Engraulis japonicus driven by fluctuations in sea temperature in the Kii Channel, Japan

Seasonal variability in the growth of larval Japanese anchovy Engraulis japonicus was examined through otolith microstructure analysis based on the samples collected from the northern side (inner area, IA) and the southern side (outer area, OA) of the Kii Channel from April 2006 to March 2007. Growth trajectories (otolith backcalculated mean standard length of 5 day intervals from 5 days after hatch to 24 days) as well as the most recent 5 day mean growth rate of larvae before capture ( G ₅) differed among months. Growth trajectories showed the same pattern as G ₅. In IA, mean ± s.d. G ₅ ranged from 0·31 ± 0·04 mm day⁻¹ (January) to 0·73 ± 0·06 mm day⁻¹ (October). In OA, mean ± s.d. G ₅ ranged from 0·36 ± 0·05 mm day⁻¹ (January) to 0·79 ± 0·11 mm day⁻¹ (August). G ₅ values declined from November to January and then started to increase. In general, the seasonal patterns of growth were similar between IA and OA, and a clear seasonal pattern in growth was identified. When the relationships among larval growth rate, sea temperature, zooplankton density and larval density were examined, growth rate was positively related with sea temperature in both areas and not related with the other factors. The similar pattern in growth observed between IA and OA was probably due to the low spatial variability in sea temperature compared to its seasonal variability.     

Effect of initial size on daily growth and survival in freshwater Chondrostoma nasus larvae: a field survey

Effects of initial size on the growth and survival of a freshwater fish, Chondrostoma nasus , were tested in a field survey, where individually tagged larvae were introduced into a potential nursery habitat. Characteristics of individual daily growth trajectories were utilized as a basis to explain growth, as well as survival patterns, in relation to ontogeny. Initial size only affected growth rates during the larval phase. Survival patterns could not be explained solely based on size-selective mortality processes because prey–predator interactions played a major role as well. This is confirmed by the Lande–Arnold selection model because directional, as well as stabilizing gradients, showed significant values. Thus, for the 0+ year freshwater fish, inherited size-specific effects were a significant advantage for growth performance and survival in early ontogeny. As fish grew older, however, other effects such as compensatory growth and prey–predator interactions apparently gained in importance.     

正弦偏心旋转诱发的豚鼠前庭眼动反射特点

目的:观察豚鼠于不同频率和偏心半径正弦旋转时相对于轴心旋转的前庭眼动反射变化特点,以提取反映前庭耳石器功能的指标,为建立其功能检测方法提供依据。方法:采用频率0.1,0.2,0.3,0.4,0.5,0.6Hz,峰速60°/s的正弦旋转刺激,分别将豚鼠置于轴心,头向外偏心半径330mm,660mm,990mm处诱发其眼震,分析不同刺激条件下的眼震增益变化规律。结果:频率和偏心半径都对眼震的增益有显著影响:同一偏心半径条件下,眼震增益随频率增加而增大;同一频率条件下,眼震增益随偏心半径增加而增大,以在0.3Hz,0.4Hz最为明显,超过此频率范围后增益随半径变化不明显。结论:提取眼震增益的增强率(enhancementratio,ER)可以表达眼震增益随偏心半径增加而增大的增强效应,并作为反映豚鼠前庭耳石器功能的指标,以0.4Hz,半径990mm的正弦旋转模式作为耳石器功能评价的刺激模式较好。     

Validation and efficacy of transgenerational mass marking of otoliths in viviparous fish larvae

Transgenerational mass marking of viviparous fish larvae in vivo was validated by intra‐muscular injection of elemental strontium chloride (SrCl₂) in gestating females and detection of the Sr in the otoliths of developing larvae. All otoliths of brown rockfish Sebastes auriculatus larvae produced from SrCl₂‐injected females showed enriched Sr:Ca ratios near the otolith edges, and the signatures did not appear to be affected by the anterior, centre and posterior positions of larvae within the ovary. Results from the present study indicate that transgenerational marking is a highly reliable technique for marking large numbers of extremely small viviparous fish larvae.     

The spatial and temporal distribution of young-of-the-year Osmerus mordax in the Great Bay Estuary

Juvenile smelt, Osmerus mordax, were collected from four eelgrass, Zostera marina, beds in the Great Bay Estuary, two within Great Bay and two located nearer the coast. Lapillar otoliths were used to estimate the ages of the smelt and to calculate daily somatic growth based on the widths of otolith increments. Smelt collected from the Bay sites were consistently younger and shorter in total length than smelt collected from the coastal sites. A repeated measures analysis of variance found significant differences among growth trajectories of smelt grouped by their dates of birth.