Seasonal change in the relationship between otolith radius and body length in age-zero Pacific saury <Emphasis Type="Italic">Cololabis saira</Emphasis>

We examined seasonal changes in the relationship between otolith radius and body length in age-zero Pacific saury Cololabis saira collected from June to December 2002–2004, based on 12,164 specimens. Results of the analysis using a generalized linear model indicated that there were differences in the intercepts among months, but no difference was seen in the slopes. In addition, post hoc analysis showed that the intercepts got larger as the month progressed from June to December. These results suggested that although the body length growth rate decreased, the growth of the otolith does not decrease to the same degree as the body after September, so the ratio of otolith radius to body length becomes larger as the months pass. Consequently, we consider that the seasonal change in relation between otolith radius and body length affects the back-calculation of body length based on otolith radius.     

Growth effect on the otolith and somatic size relationship in Japanese anchovy and sardine larvae

ABSTRACT:   Relationships between otolith and somatic sizes were examined for Japanese anchovy Engraulis japonicus and sardine Sardinops melanostictus larvae collected broadly in the western North Pacific, based on a substantial data set derived from a previous paper. Allometric formulae showed close fits to the relationships between otolith radius and standard length, and the formulae differed between anchovy and sardine larvae. Despite the high correlations, the effect of somatic growth rate on the otolith and somatic size relationship (the 'growth effect') was significantly detected for both anchovy and sardine larvae. Slower growing larvae tended to have larger otoliths than faster growing conspecifics at the same somatic size. This growth effect was more obvious for sardine larvae than for anchovy larvae, probably because of their differential responses of somatic growth to temperature shifts. The growth effect could lead to the possibility of biases in the back-calculation and size estimation processes. As the growth effect is considered to be a general phenomenon and its extent to be species-specific, the relationship between otolith and somatic size and its uncoupling should be scrutinized before application of techniques based on the otolith and somatic size correlation.     

Somatic growth and otolith microstructure of larval and juvenile pacific cod <Emphasis Type="Italic">Gadus macrocephalus</Emphasis>

ABSTRACT:   Microstructures of sagittae and lapilli were examined in relation to somatic growth for reared larvae and juveniles of Pacific cod. The Laird–Gompertz model was fitted to the daily age and somatic growth relationship. Growth increments were deposited on a daily basis in both kinds of otoliths, with a check formed at hatching. Two subsequent checks and an accessory primordia (AP) occurred in the sagittae. The lapillus was adequate for increment width measurement through the early life stages. Sagittal and frontal plane of sagitta was adequate for measurement in the pre-AP and post-AP formation stages, respectively. The shift of desirable plane was caused by changes in otolith and increment shapes with AP formation. Back-calculated total lengths using the biological intercept method did not significantly differ with certain body lengths ( P  > 0.05), suggesting validity of back-calculation in this species. Using the back-calculated total length, morphological and ecologic changes that seemed to affect checks and AP formations are discussed.     

Validation of daily increment formation in otoliths of immature and adult Japanese anchovy <Emphasis Type="Italic">Engraulis japonicus</Emphasis>

In order to validate daily increment formation in otoliths of immature and adult Japanese anchovy Engraulis japonicus, three rearing experiments using chemical marking of otoliths were conducted on adult anchovy in summer 2004 and immature anchovy in summer 2005 and in winter 2006. In the two experiments conducted in summer, the number of otolith microincrements between alizarin complexone (ALC) marks showed that microincrements were formed daily. In the summer 2005 experiment, immature anchovy under conditions of reduced daily food rations also showed daily microincrement formation. Average increment width was 0.9 μm in adults and 1.8–3.1 μm in immature anchovy. In contrast, no clear increments were observed between ALC marks on the otoliths from the experiment in winter 2006, and scanning electron microscope (SEM) observations failed to confirm clear increment formation. We consider that low water temperatures (<13–14°C) restricted otolith growth and lowered the contrast between the discontinuous and the incremental zones of the otolith increments. For age estimation of Japanese anchovy, clear increments wider than about 1 μm in the otolith can be regarded as daily increments. However, daily age estimation of immature and adult anchovy that experience low water temperatures in winter may be difficult due to the obscurity of the increments.     

Otolith microstructure of chum salmon <Emphasis Type="Italic">Oncorhynchus keta</Emphasis>: formation of sea entry check and daily deposition of otolith increments in seawater conditions

To apply otolith microstructure to examination of age and growth of juvenile chum salmon Oncorhynchus keta inhabiting coastal waters, formation of otolith increments was investigated for juveniles reared in a seawater aquarium and in net pens. In all otoliths examined, a distinctive check was formed at the time of sea entry of the fish. The deposition of otolith increments after the check was daily for rearing both in the aquarium (57 days) and in the net pens (26 days). Check formation associated with sea entry was also observed in otoliths of juvenile salmon collected 1 km off the coast of Shari, Hokkaido, Japan. Transmitted light observation of otoliths of those fish revealed a transition in otolith increment appearance from dark to light. Otolith Sr: Ca ratio remarkably changed from a low to a high level, coinciding with the transition in otolith appearance. It is suggested that the transition was associated with individual sea entry. This study demonstrated that the check and/or transition associated with sea entry are applicable to a benchmark for otolith increment counts of juvenile chum salmon inhabiting coastal waters.     

Daily and sub-daily otolith increments of larval and juvenile walleye pollock, Theragra chalcogramma (Pallas), as validated by alizarin complexone experiments

Walleye pollock (Theragra chalcogramma) were reared from eggs to the juvenile life stage to study daily increment formation in the sagittae otoliths, which are routinely used for age and growth analyses. The apparent deposition of sub-daily growth increments becomes problematic for determining fish age from the late larval stage throughout the juvenile (young-of-the-year) development stage. Otolith marking experiments were conducted to determine interpretation criteria to differentiate between daily and sub-daily increments. Immersion of larval and transforming walleye pollock in 25 mg/l of alizarin complexone (ALC) for 6 h once a week produced a fluorescent mark on the day of staining. Evidence of six well defined and equally spaced increments counted between the weekly ALC marks validated the deposition of daily increments. The daily increments gradually increased in width as the fish/otolith grew. The criteria for determining the presence of sub-daily increments between the daily increments were (1) weak optical definition and (2) a sudden change in incremental distance that lasted for one or two increments and were approximately <0.5 μm in width. Growth problems that occurred during the experiments were identified on otoliths as reductions in daily incremental widths and optical definition, which continued for several days. Otoliths from field-collected fish have also shown similar changes in daily increment properties during the juvenile stage, which may be an indicator of an environmental influence. The criteria for defining different increment types help to resolve our current age determination issues for late larval and early juvenile stage walleye pollock from the Gulf of Alaska.     

Otolith development and daily increment formation in laboratory-reared larval and juvenile black-spot tuskfish <Emphasis Type="Italic">Choerodon schoenleinii</Emphasis>

Microstructures of lapilli were examined for reared larvae and juveniles of black-spot tuskfish Choerodon schoenleinii. Lapilli of larvae at 1 day after hatching have one diffuse and obscure ring with an otolith radius of 4.3 ± 0.50 μm (mean ± SD, N = 8). The slope and intercept of the regression between the number of days after hatching and increment counts did not differ significantly from one and zero, respectively, indicating that lapillus increments were formed on a daily basis after hatching. There was an ontogenetic shift in the relative values of somatic and otolith growth, which corresponded to the transition from pelagic larvae to settlement stage. Simultaneously, the daily increment width reached the maximum value. These findings suggest that age at maximum value of increment width can be used as an indicator of the planktonic larval duration while settlement mark is not found. Since ontogenetic shift in the relationship between otolith radius and body size was observed, back-calculation of somatic growth in black-spot tuskfish using the otolith radius during the early life stages should be analyzed with caution, and the method requires further validation.     

Parallelism in thermal growth response in otoliths and scales of brown trout (Salmo trutta L.) from alpine lakes independent of genetic background

Low density in natural populations of salmonids has predominantly been managed by stocking of non‐native conspecifics. Due partly to domestication, introduced non‐native fish may be maladapted under natural conditions. Interbreeding between introduced and wild individuals may therefore impair local adaptation and potentially population viability. Brown trout (Salmo trutta L.) from three headwaters (with stocked fish) and three interconnected lakes (with native fish) on the Hardangervidda mountain plateau, southern Norway, were tested for differences in thermal effects on scale and otolith growth. Otolith and scale annuli widths from immature brown trout showed positive correlation with mean annual summer temperature for all six sampled populations. In mature individuals, a similar positive thermal correlation was evident for the otoliths only. Interannuli width measurements from scales indicate a halt in somatic growth for brown trout in this alpine environment when reaching ages between 7 and 9 winters, coinciding with age at maturity. Our study indicates that otolith growth follows summer temperature even when individuals do not respond with somatic growth in these populations and that introduced brown trout and introgressed populations have similar thermal growth responses. Due to the continued otolith growth after stagnation in somatic growth and the impact of fluctuations in summer temperature, the utilisation of otolith annuli widths for back calculation of length at age should be treated with caution.     

Age validation,growth and annual reproductive cycle of chub mackerel <Emphasis Type="Italic">Scomber japonicus</Emphasis> off the waters of northern Kyushu and in the East China Sea

The age and growth of chub mackerel Scomber japonicus collected from the East China Sea and the northern waters off Kyushu between June 2000 and June 2001 were determined by observing the otolith surface after dipping it in xylene. The translucent and opaque zones on the otolith surface were identified, and the number of translucent zones was counted. Monthly changes in the frequency of fish with translucent zones on the otolith margin, and in the marginal increments, indicated that the translucent zones were formed between April and June. The seasonal pattern of annulus formation on the otolith became clear by observing the otoliths of fish with known ages, and the otolith formation in wild fish was consistent with that of fish with known ages. The mean gonadosomatic index of male and female fish was high from March to May, and spawning females were observed from mid-March to mid-May. The estimated ages were 1–5 years for males and 1–6 years for females. The von Bertalanffy growth parameters did not significantly differ between male and female. The model was obtained as FL _t=406×{1−exp[−0.372×(t+1.68)]     

Does otolith macrostructure record environmental or biological events? The case of black hake (Merluccius polli and Merluccius senegalensis)

Fish age determination using otoliths requires a prior understanding of growth mark deposition patterns (translucent rings, TR) as well as their connection with internal or external events experienced by the fish. This study analysed the macrostructural seasonal ring deposition pattern observed in transversal sections of black hake otoliths. A total of 793 black hake otoliths were collected in autumn and spring 2007 from research and commercial surveys carried out in continental and shelf waters off Mauritania. Most of the Merluccius polli otoliths presented narrow and wide translucent rings (NTR and WTR, respectively) regardless of fish size, whereas Merluccius senegalensis otoliths only showed NTR. This seemed to be a sign of ontogenetic discrepancy between the two black hake species, whose otoliths confirmed the existence of significant differences in their growth patterns.The frequency distributions of the number of TR counted along the ventral radius (VR) of the otolith from the nucleus (birth date) and from the ventral edge (death date) were analysed to ascertain whether a specific endogenous event (Hypothesis A) or a precise environmental event (Hypothesis B) could restrain growth leading to the formation of TR. The general TR frequency distribution pattern was somewhat similar for both hake species, which showed marked TR at comparable distances. Within each species, TR frequency distributions of their distances from the nucleus along the otolith VR were quite similar between sexes, seasons, and fish sizes. Our results support the idea of a coincident biological event, such as first maturity, slowing down the growth process and thus provoking the formation of TR in otoliths of both species.This study also experience difficulty using the complex and highly variable macrostructural pattern of black hake otoliths to establish age interpretation criteria for these two species.     

长江口凤鲚仔稚鱼不同发育阶段矢耳石生长

2014年4—8月于凤鲚(Coilia mystus)的主要繁殖期在长江口采集仔稚鱼103尾。分析凤鲚仔稚鱼样本得出日龄范围为5~48 d,体长为4.20~26.21 mm。为研究长江口凤鲚早期发育不同阶段生长,测定了凤鲚仔稚鱼(5~48日龄)体长随日龄的生长变化,其变化分为3个阶段(5~11日龄、12~30日龄、31~48日龄)。不同日龄阶段,体长的生长速率差异性显著(P0.05)。耳石早期发育研究发现耳石长、耳石宽随鱼体的生长而增长,在17~19日龄之后其生长速率增大约2倍。采用分段回归方法分析耳石长、耳石宽与日龄的关系,发现二者异速生长的拐点均出现在19~20日龄,拐点前为慢速生长,之后为快速生长。研究发现凤鲚早期生长发育阶段的耳石形态有较为显著的改变:卵黄囊期、前弯曲期为圆形;弯曲期耳石长的生长大于耳石宽的生长,耳石逐渐变成椭圆形;耳石变成稳定形态后,长宽比基本保持稳定。     

Otolith biochronologies as multidecadal indicators of body size anomalies in yellowfin sole (Limanda aspera)

Dendrochronology (tree‐ring analysis) techniques have been increasingly applied to generate biochronologies from the otolith growth‐increment widths of marine and freshwater fish species. These time series strongly relate to instrumental climate records and are presumed to reflect interannual variability in mean fish condition or size. However, the relationship of these otolith chronologies to fish somatic growth has not been well described. Here, this issue was addressed using yellowfin sole (Limanda aspera) in the eastern Bering Sea, for which a 43‐yr otolith chronology was developed from 47 otoliths and compared with body size for 6943 individuals collected in 1987, 1994, and 1999 through 2006. Among several metrics of size normalized for age and sex, average body mass index (defined as weight/length) had the strongest relationship to the otolith chronology, especially when the chronology was averaged over the 5 yr preceding fish capture date (R² = 0.88; P < 0.001). Overall, sample‐wide anomalies in otolith growth reflected sample‐wide anomalies in body size. These findings suggest that otolith chronologies could be used as proxies of body size in data‐poor regions or to hind‐cast somatic growth patterns prior to the start of fisheries sampling programs.     

阿根廷外海拉式南美南极鱼矢耳石形态特征分析

拉式南美南极鱼(Patagonotothen ramsayi)矢耳石形态存在多样性,这为该鱼种地理种群鉴定提供了重要参考。为深入研究拉式南美南极鱼矢耳石外部形态特征,利用2014年12月~2015年4月间采集的166ind拉式南美南极鱼(体长范围95~288 mm)样本,对其矢耳石形态进行观察与测量,并对其形态特征进行了分析。结果表明,拉式南美南极鱼耳石具有明显的基叶和翼叶,其主间沟、主凹槽、缺刻和辐射状条纹明显清晰,呈狭长状,内侧凸面、外侧凹面。左、右耳石的背宽和翼叶长存在显著性差异,但耳石长度、宽度、基叶长、背长、周长和面积不存在显著差异。耳石各形态参数值随着体长的增加,其绝对尺寸不断增加,而相对尺寸逐渐减少,其形态结构的比例基本不变。耳石的长度、宽度与耳石质量均表现为乘幂函数关系,随着耳石质量的不断增加,其长度、宽度也不断增加。耳石的长度、背长、基叶长、翼叶长、周长和面积与鱼体体长呈乘幂函数关系,宽度和背宽与体长呈线性函数关系;耳石的各形态参数值与湿重均呈显著的乘幂函数关系。     

云龙湖水库青梢鲌的生长特性

采用鳞片和耳石对取自云龙湖水库的青梢鲌(Erythroculter dabryi)进行了年龄鉴定,并对其生长特性进行分析。结果显示:以鳞片和耳石为年龄鉴定材料时,二者的吻合率分别为59.57%和90.16%。年龄鉴定结果显示,所捕获的青梢鲌由1~8龄个体组成,主要是3~5龄个体;个体体长与耳石半径之间呈直线相关:L=9.5632R-0.1595(R2=0.995,n=175),体重与体长呈指数函数相关:W=1.07×10-2L3.3035,其生长规律符合von Bertalanffy方程:Lt=20.4741(1-e-0.2531(t+0.8056)),Wt=229.5864(1-e-0.2531(t+0.8056))3.3035;青梢鲌生长拐点年龄为3.92龄,对应的体长为14.28 cm,体重为69.88 g;3.92龄为合理的捕捞时期。     

Age validation and growth variability of Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis> off the Pacific coast of northern Japan

ABSTRACT:   This study examined age and growth of Japanese flounder Paralichthys olivaceus off the Pacific coast of northern Japan, and determined whether the growth patterns of male and female fish in northern (40–41°N) and southern (37–38°15'N) waters differ. In total 8095 specimens were collected between January 1999 and December 2005. Zonation consisting of opaque and translucent bands on the otolith was evident. Within each opaque band a thin and clear check (ring mark) was observed in all specimens examined. Monthly change in the frequency of appearance of a ring mark on the outer margin of the otolith indicates that ring marks form between July and August. The von Bertalanffy growth model showed a sexual dimorphism in growth, as females grew faster and reached a larger size than males. The growth patterns obtained by tracking the observed total length for monthly collections showed a rapid increase in total length between August and October. Spatial variation in the growth pattern of male and female fish between northern and southern waters was evident, as southern fish were significantly larger than northern counterparts during 1.25–3.00 years post hatch.     

Identification of hatchery-reared and naturally produced Atlantic salmon, Salmo salar L., juveniles based on examination of otoliths

. Atlantic salmon, Salmo salar L., parr and smolts from three Norwegian rivers were examined with respect to whether or not they had been released from a hatchery. The hatchery background was known for some released fish and could be ascertained for others from their aberrant body morphology and eroded fins. Fish released after one winter in a hatchery had opaque otoliths like the fish examined from two hatcheries. Naturally produced fish showed a distinct, seasonal growth pattern in the otoliths, alternating between opaque summer zones and hyaline winter zones. Fish released as fry showed an otolith pattern similar to that of naturally produced fish. A test revealed little discrepancy between two independent otolith readings even though the test reading was conducted without any information about the fish accompanying the otoliths. The results suggest that examination of otoliths may help distinguish between juveniles that are hatchery-reared and juveniles that are naturally produced in the river, provided that the hatchery-reared fish have a 1-year history in the hatchery prior to release.     

Interannual variability in hatching period and early growth of juvenile walleye pollock, Theragra chalcogramma, in the Pacific coastal area of Hokkaido

Juvenile walleye pollock of the Japanese Pacific population were collected from the Funka Bay [spawning ground; 16–64 mm fork length (FL)] in spring and the Doto area (nursery ground; 70–146 mm FL) in summer. Hatch dates were estimated by subtracting the number of otolith daily increments from sampling dates, and their early growth was back‐calculated using otolith radius–somatic length relationships. Interannual change of the hatching period was observed during 2000–02, and the peaks ranged from mid‐February in 2000 to early‐April in 2002. In 2000, when a strong year class occurred, early life history of the surviving juveniles could be characterized by early hatching and slower growth in the larval stage (<22 mm length). Higher growth rate in 2001 and 2002 did not always lead to good survival and recruitment success. Even though their growth was slow in 2000, the larvae hatched early in the season had larger body size on a given date than faster‐growing larvae hatched in later season in 2001 and 2002. Bigger individuals at a certain moment may have advantage for survival. The delay of hatching period may result in higher size‐selective mortality, and as a necessary consequence, back‐calculated growth in 2001 and 2002 could shift towards higher growth rate, although abundance of such a year class would be at the lower level. Variability in spawning period, early growth and their interaction might have a strong relation to larval survival through cumulative predation pressure or ontogenetic changes in food availability.     

Responses in growth rate of larval northern anchovy (Engraulis mordax) to anomalous upwelling in the northern California Current

We examined variability in growth rate during the larval stage of northern anchovy (Engraulis mordax) in response to physical and biological environmental factors in 2005 and 2006. The onset of spring upwelling was anomalously delayed by 2–3 months until mid‐July in 2005; in contrast, spring upwelling in 2006 began as a normal year in the northern California Current. Larval and early juvenile E. mordax were collected in August, September, and October off the coast of Oregon and Washington. Hatch dates ranged from May to September, with peaks in June and August in 2005 and a peak in July in 2006, based on the number of otolith daily increments. Back‐calculated body length‐at‐age in the June 2005 hatch cohort was significantly smaller than in the August 2005 cohort, which had comparable growth to the July 2006 cohort. Standardized otolith daily increment widths as a proxy for seasonal variability in somatic growth rates in 2005 were negative until late July and then changed to positive with intensification of upwelling. The standardized increment width was a positive function of biomass of chlorophyll a concentration, and neritic cold‐water and oceanic subarctic copepod species sampled biweekly off Newport, Oregon. Our results suggest that delayed upwelling in 2005 resulted in low food availability and, consequently, reduced E. mordax larval growth rate in early summer, but once upwelling began in July, high food availability enhanced larval growth rate to that typical of a normal upwelling year (e.g., 2006) in the northern California Current.     

国内外对鱼类耳石日轮的研究和应用

人类对鱼类耳石日轮的研究开始于七十年代初。到目前为止，国内外许多学者对多种海水、淡水鱼类的耳石日轮进行了研究。本文简要介绍了这方面的研究结果，其中包括耳石日轮的结构，日轮的形成与环境之间的关系，日轮研究在其它领域中的应用，以及目前该研究工作存在的问题。     

多鳞四指马(鱼友)耳石形态特征的观察

利用2010年2月～2012年5月从江苏启东、福建东山、海南海口、广东湛江和台湾沿海海域采集到的192 ind多鳞四指马(鱼友)(Eleutheronema rhadinum)标本,取3对耳石,并以矢耳石长、宽、重、长宽比、面积、周长、矩形趋近率、成形系数、密度等指标为基本形态学参数,研究多鳞四指马(鱼友)的耳石形态特征。结果显示,多鳞四指马(鱼友)矢耳石都有基叶和翼叶,中央听沟明显,前缘开阔,后缘窄且闭合。矢耳石的大小和形状随个体生长变化明显,叉长较短的样品,耳石呈瓜子状,边缘规则;叉长较长的样品,矢耳石呈狭长叶片状,边缘有较多波浪形突起。矢耳石形态特征比较显示:多鳞四指马(鱼友)矢耳石在形态上更接近鲈形目鱼类耳石形态,这支持将多鳞四指马(鱼友)归为鲈形目鱼类。矢耳石平均密度为0.80 mg·mm-3,平均矩形趋近率为0.70,成形系数为0.58,耳石长是叉长的2.82%～3.42%,重量占体重的0.06‰～0.59‰。矢耳石度量指标的变异系数均小于其叉长、体重的变异系数,矢耳石形态的稳定性高于其身体形态的稳定性。多鳞四指马(鱼友)矢耳石长、宽、重、长宽比与叉长呈显著相关,耳石长与宽符合幂函数关系。密度、矩形趋近率、成形系数、耳石长占叉长比、耳石重占体重比等参数可以作为表征参数,来衡量多鳞四指马(鱼友)的形态特征。