In this study, a single specimen of Pacific black scabbardfish Aphanopus arigato Parin, 1994 was collected at a depth of ~500 m near Dongsha Island in southwestern Taiwan (18°49′ to 20°45′N and 112°46′ to 116°15′E), on 14 March 2023. This is the southernmost record of A. arigato, with a significantly wide range extension from northern Japan, and southern Kuril Islands to the South China Sea. We also provide comparisons of the morphological measurements, first description of sagittae otoliths, and a partial sequence of the cytochrome oxidase subunit I gene for the specimen studied in this study.

Sagittal otolith morphology and otolith shape of two megrim species, Lepidorhombus boscii and Lepidorhombus whiffiagonis, were compared using descriptive morphological characters and Wavelet shape coefficients. Differences in otolith shape were examined by linear discriminant analysis (LDA). The first discriminant axis explained 66.6% of the variation between the groups, and the second axis 28.5%. Otolith classification based on LDA showed that in 79.5% of cases an otolith can be correctly classified based only on its shape. Relationships between otolith morphometric parameters (length and width) and fish size (total length) were described by fitting simple linear regression models. For L. boscii the highest positive correlation was found between right otolith width and total body length (R2 = 0.82), and for L. whiffiagonis between left otolith length and total body length (R2 = 0.39).

The catch of Japanese butterfish, Psenopsis anomala in Taiwan is greater than those of any other nation; however, the biology, particularly the age and growth, of this economically important fish species is little known. This study describes the age and growth of P. anomala based on 734 specimens (340 females, 363 males, 31 unsexed) caught by trawl fishery in the north-eastern waters off Taiwan from March 2007 to July 2008. The age of specimens was estimated by counting the growth annuli in sagittal otoliths. The periodicity of annulus deposition on otolith was estimated to be one year with opaque zone deposited between July and August based on marginal increment analysis. The maximum age for both sexes was estimated to be ~4. The female portion of the population was dominated by the 3+ age class, while the male portion was dominated by the 2∞ age class. The parameters of the von Bertalanffy growth function with standard error estimated based on the observed length at age using a non-linear method are as follows: L∞ = 25.47 ± 0.65 cm, k = 0.30 ± 0.03 year−1, and t0 = −1.84 ± 0.16 year for females (n = 350), and L∞ = 22.39 ± 0.45 cm, k = 0.46 ± 0.04 year−1, and t0 = −1.38 ± 0.13 year for males (n = 378). The growth performances of P. anomala reported from different geographic regions were compared, and the potential influences of sample size distribution on the estimated growth parameters were further discussed.

Age and growth parameters were estimated for the deep-sea cardinalfish (Epigonus crassicaudus) from sagittal otoliths collected between 2012 and 2015 onboard commercial fishing vessels from the South-east Pacific off Chile between 33°04′S and 41°46′S. Von Bertalanffy growth parameters (VBGP) were estimated from assumed annual otolith growth zone counts. The verification of the first annulus of sagittal otoliths was determined by examining in detail daily micro-increments. These data helped inform the interpretation of the annual growth zones from transverse otolith sections. The von Bertalanffy growth model estimated to length-at-age data were asymptotic length (L∞) of 34.1 cm fork length (FL), a growth coefficient (k) of 0.1 cm/year and a t-zero (t0) of −0.85. The maximum ages observed were 67 and 65 years for female and male fish, respectively.

The paper presents the first detailed study on systematics, otolith structure and biology of Diaphus coeruleus, from the south-eastern Arabian Sea. The closely related and co-inhabiting species D. coeruleus and D. watasei are distinguished on the basis of morphometric, meristic and otolith characters. Analysis of gut content revealed that these fishes mainly feed on deep sea squids and shrimps. Six maturation stages of gonads are identified in males (immature, quiescent, mature, ripe, spawning and spent) and five stages (immature, quiescent, mature, ripening and spawning stages) in females. Overall sex ratio deviated in favour of males (1 male: 0.2 female) and the mean fecundity was 2150 ± 353 eggs. The length-weight relationship shows an overall isometric growth in males with N = 76 and b = 3.13 and for females with N = 17 and suggests negative allometric growth (b = 1.719). Otolith length (LO) and otolith weight (WO) are positively correlated to standard body length (LS) and body weight (BW).

Mugil liza is distributed along the western Atlantic coast. It is a commercially exploited species in Argentina, supporting a small-scale fishery conducted by an artisanal fleet. Age determination of fishes constitutes an important key issue for fishery management. The age, growth and recruitment of M. liza juveniles in Mar Chiquita coastal lagoon and Las Brusquitas creek (Buenos Aires, Argentina), were estimated by means of the analysis of the sagittal otoliths of fish collected during January to December of 2014. Ages were estimated by counting and measuring daily growth increments in otoliths under a light microscope. A total of 735 specimens ranging from 19 to 71.5 mm SL and from 67 to 212 days age was analysed. Lengths at previous ages were determined by back-calculation, a linear growth model was fitted to the back-calculated data: SL = 0.2468 + 2.0516; R2 = 0.9945. Two peaks of recruiters were observed from February to March, and from October to November in 2014. Mean ages in days of Querimana and juveniles at the recruitment time were 84.07 ± 14.43 days and 87.56 ± 19.51 days, respectively. The hatching dates of specimens showed two spawning seasons. One was from December 2013 to January 2014, and the second one from July to August 2014. The assessment carried on this work generated age determination values that support previous findings, contributing to make a more accurate description of the life-history model currently used. In addition, valuable information has been generated to give better advice for improving the management of the fishery resource.

Early life traits (ELT) of the sand-burrowing cryptic marine fish Sindoscopus australis (family Dactyloscopidae) were compared between cohorts hatched during winter and spring 2013, in nearshore rocky reefs off central Chile. Pelagic larvae were similarly abundant during both periods, but larger larvae were collected during austral spring. The sagittal otolith microstructure and size analyses also indicated that size-at-hatch was larger (4.7 mm) for the winter cohort, but winter larvae experienced slower growth rates (0.145 mm day−1 ± 0.008). Conversely, larvae from the spring cohort hatched at smaller sizes (2.9 mm), but they grew faster (0.182 mm day−1 ± 0.008). Hatching periods were coupled with the lunar cycle; in winter, hatching events were related to neap tides (first and third quarter moon), increasing chances of self-recruitment. Meanwhile, during spring, hatching occurred during spring tides, particularly over the new moon, decreasing chances of larval mortality by predation. Otolith traits used to test asymmetry among cohorts showed inconsistent results. Only sagittal perimeter presented fluctuating asymmetry, showing higher variance for the winter cohort. We conclude that this burrowing species displays different reproductive tactics at a seasonal scale.

Pseudapocryptes elongatus is one of the oxudercine gobies, which show varying degrees of amphibious behaviour and capacities to breathe air. There is little information on the early life history of P. elongatus, particularly of their morphology and larval habitat and duration. This study focused on the life history of larval and juvenile stages of P. elongatus investigated by genetic species identification, morphological observation and otolith analyses using specimens collected in June and October 2012 from estuaries in Bac Liêu Province, southern Vietnam (09°14′N 105°43′E). Genetically identified juvenile P. elongatus were characterized by (1) a slender body form, (2) the anterior edges of both the anal and second dorsal fins located at the midpoint along the body axis, (3) scarce chromatophores over the body surface, (4) melanophores in the parietal region between the eyes, and (5) a single row of melanophores along the base of the anal fin. Mean age at recruitment to estuaries was 38.0 ± 4.1 days, and otolith Sr/Ca ratios ranged from 8.9 to 9.9 mmol mol−1, suggesting that larval migration from their spawning sites requires more than 1 month in saline environments.

Age and growth of Agassiz's parrotfish Sparisoma frondosum captured off Brazil (Pernambuco) were estimated using sagittal otoliths from 251 specimens. Sex of each specimen was determined and showed that 130 specimens were females (13.1 to 36.8 cm TL) and 121 were males (17.5 to 36.6 cm TL). The otolith marginal increment analysis indicated a single translucent ring formed every year. Parameters of growth curves were derived for the von Bertalanffy (VBGF) and Gompertz models. Based on the Akaike information criterion (AIC), both models were suitable for describing the growth of this species. VBGF parameters were estimated for males L ∞ = 39.74 cm TL, K = 0.22, t 0 = −1.63 years, females L ∞ = 32.38 cm TL, K = 0.44; t 0 = −0.23 years; and for the sexes combined L ∞ = 33.66 cm TL, K = 0.41, t 0 = −0.27 years. The study showed that 55% of individuals were 3 and 4 years of age, with maximal age of 9 years. Mature females (>17.6 cm TL) accounted for 45% of the sample. The age at first maturity for females was 1.6 years. For males the size at first maturity was not determined as immature individuals were not present in the overall sample. Also, primary males (PM) and specimens with gonads undergoing sexual transition were not found. The age structure and growth parameters for S. frondosum are an important contribution to the assessment of the state of exploitation of this species.

This is the first record of the black scorpionfish Scorpaena porcus being found in the eastern English Channel. A specimen was caught on 15 October 2012 off the port of Courseulles-sur-mer. It measured 31.6 cm and weighted 800 g. From a study of its sagittal otolith, this specimen appeared to be 9 years old.

A sample of 3393 garfish, Belone belone (Linnaeus, 1761) was captured using a seine net between January 2003 and December 2008, along the eastern Adriatic Sea. The range in total length was 20.8–75.4 cm and in weight was 12.21–639.25 g. Length–length equations for converting size measurements (standard length and fork length to total length (TL)) were linear. In the length–weight relationship, positive allometry was established (b = 3.4818). Age, determined from sagittal otoliths, ranged from 1+ to 8+ years. The estimated von Bertalanffy model growth parameters for garfish were L∞  = 90.3 cm, K = 0.158 year−1, t0  = −0.109. Otolith weight was endorsed as a possible age predictor, as it showed highly exponential correlation with total garfish length and age (Wo  = 0.0012 TL 2.189; Wo  = 0.568t1.486). These findings were used to examine mortality rates and exploitation in order to improve conservation and management of this pelagic species.

Otolith microstructure analysis was used to reveal daily growth patterns of young-of-the year (YOY) of six species of perciform fishes, Bovichtus chilensis (Bovichtidae), Girella laevifrons and Graus nigra (Kyphosidae), Helcogrammoides chilensis (Tripterygiidae) and Hypsoblennius sordidus and Scartichthys viridis (Blenniidae). YOY collected in intertidal pools from June to December 2008 in Central Chile, ranged from 24 to 76 mm total length and from 25 to 390 days of age. In the six species, sagittal otoliths showed a slightly oval shape, symmetrical and laterally compressed and showed micro-increments distinguishable after a two-side polishing. Increment width of sagittae showed two patterns irrespective of hatch month and species: (i) a parabolic growth with wider increment widths (during the first 150 of YOY life, e.g. B. chilensis, G. nigra and G. laevifrons); and (ii) a more irregular pattern with lower increment widths during most of the seasons in H. chilensis and H. sordidus. Further results were: (i) a unique central primordium enclosed by two checks after which distinctive increments were deposited; (ii) low instantaneous growth rates estimated through the slope of the length-at-age relationship (range 0.1–0.21 mm d−1 ); and (iii) a linear fish size–otolith size relationship.

The finding of a specimen of Eretmophorus kleinenbergi (Moridae) stranded on the shore on the Sicilian coast of the Strait of Messina (central Mediterranean Sea) is reported. Morphometric and meristic characters are given, and the description of sagittal otoliths and a colour photograph of a fresh specimen are provided.

In Amazonian fisheries, the silver arowana, Osteoglossumbicirrhosum (Cuvier 1829) is heavily exploited for humanconsumption as an adult, and for the aquarium trade as a small juvenile(yolk sac juvenile mainly). The periodicity of annuli formationon otoliths and growth variability of the silver arowana were studied indifferent river river-basins of the Peruvian Amazon between 2006and 2009. Transverse stained sections of 606 individual otolithswere analysed from four different river-basins, the Amazonas, Ucayali,Napo and Putumayo, of which 554 could be interpreted. These belongedto 274 females ranging from 15 to 91 cm (standard length) and 280males ranging from 30 to 91 cm. In addition, yolk sac juvenilesof known age were collected to improve growth modelling. Monthlyproportions of stained otolith edges validated the formation ofa single annulus per year in two different river-basins with laggedhydrological cycles: the Amazonas-Ucayali and the Putumayo. Stainedgrowth mark counts resulted in a longevity estimate of at least16 years for the silver arowana in the Peruvian Amazon. This fishgrew quickly during the first two years, and asymptotic growth wasreached after four to five years, except in the Putumayo where itwas reached slightly earlier. Results showed no significant growthdimorphism between sexes within basins, but indicated significantgrowth differences among river basins. Silver arowanas measured,on average, between 38 and 40 cm at the end of their first year.Length-at-age differences among river basins increased with ageto reach over 14 cm (and >3 kg) after 7 years between the fasterand slower growing populations (Amazonas and Putumayo, respectively).The growth differences observed emphasize the need for further investigationon the population structure of this species as, although these differencesmight merely be phenotypic responses to contrasted environmentalconditions, they could alternatively reflect the existence of severalpopulations with distinct genetic and life history characteristics.The consequences of such differences would be very important forthe management and conservation of this fragile and extensivelyexploited species.

Otolith shape analyses were conducted on three differentspecies of Mullidae (Mullus barbatus barbatus, M.b. ponticus and M. surmuletus). The otolithshape was described by 19 harmonics from elliptic Fourier descriptors. Ina first step, their comparison through canonical discriminant analyses(CDA) was run for all fish with right otoliths, left otoliths andboth otoliths pooled. The latter possibility had a higher discriminatingpower and allowed much more visually explicit results. This impliedthat the two otoliths were not similar as often claimed, and hadeach their specific information. In a second step, the CDA demonstratedstrong spatial discrimination of local populations from variousareas within the Mediterranean basin, i.e. NW Mediterranean, AegeanSea and Black Sea, and between sites within each area. The percentageof well classified individuals of M. barbatus inpredefined groups varied between 78 to 100% depending on sites,and even reached 100% for each site for M. surmuletus.These spatial patterns were most likely linked to differences inenvironmental conditions between areas and sites, such as effectsof strong river runoffs and differences in depths and/or habitattypes. In a third step, CDA also evidenced ontogenetic discriminationsof mullet populations that could be linked (i) to influence of dietof fish of various sizes and (ii) to changes in physiological conditionsaccording to the stage of development of the fish.

The understanding of the stock structure of a species is essential to effectively manage fisheries. Otolith shape analysis has been successfully applied in stock identification using the elliptic Fourier analysis. This method was used to assess possible differences in the otolith shape of Helicolenus dactylopterus caught around the Azores, Madeira and mainland Portugal. A total of 294 individuals ranging from 23 to 29 cm in total length, equally distributed by sex and area, were analysed. The multivariate analysis of variance performed on the otolith normalized elliptic Fourier descriptors (NEFDs) revealed significant differences for both area and sex, but no interaction was found between the two factors. In the canonical discriminant analysis an overall classification success of 69.4% and 66.7% was achieved for females and males respectively. These results suggest the usefulness of otolith shape analysis for stock differentiation of bluemouth from Portuguese waters.

The use of genetic, biochemical and electronic markers in population biology and ecology has been growing tremendously during the last two decades. The first part of this paper aims at reviewing the main principles and advances of these individual markers through a few key applications on exploited marine fish populations. The second part is more prospective and investigates some possibilities that could arise in the near future through: (i) the development of new markers, (ii) the combination of different markers and (iii) the combination of quantitative approaches -whether classical or new- with individual markers. It is finally stressed how crucial individual markers will be to unravel the biocomplexity of wild fish populations and the key role they should play in the implementation of the ecosystem approach to fisheries.

The life histories of Plecoglossidae and Osmeridae fish collected from Japanese fresh, brackish, and seawaters were studied by examining the strontium (Sr) to calcium (Ca) ratios in their otoliths. The Sr:Ca ratios in the otoliths changed with the salinity of the habitat. The fish living in a freshwater environment showed consistently low Sr:Ca ratios throughout the otolith. The fish were identified as a standard freshwater type. In contrast, fish collected from the intertidal zone showed higher otolith Sr:Ca ratios than those in the standard freshwater type, and the ratios fluctuated along the growth phase. In the present study, in addition to the representative migration pattern reported previously, other migration patterns were found to show consistently high Sr:Ca ratios throughout the otolith in several Osmeridae fish. Those results indicate that these fish have a flexible migration strategy with a high degree of behavioural plasticity and an ability to utilize the full range of salinity throughout their life history.