Otolith Microstructure Research Articles

Early life history traits and elevated growth trajectories associated with survival into winter in range-expanding coral reef fish

Climate change is driving the poleward range expansion of sub-tropical and tropical marine species into temperate ecosystems, with ocean-warming hotspots experiencing rapid shifts in species distributions. While recruitment to temperate waters by expatriating tropical vagrant fish is increasing, surviving through the cooler winters remains a significant barrier to their establishment. This study investigates the links between early life history traits and survival into winter in the Sergeant Major (Abudefduf vaigiensis), a tropical damselfish expanding its range into temperate southeastern Australia. Using otolith microstructure analysis, we reconstructed the early life histories of 122 individuals collected from rocky reefs in Sydney (33.8oS) Australia in 2022 and 2023 and assessed their early life history traits. Our results demonstrate that individuals sampled during winter (hereafter “wintered fish”) had a larger size at hatching, longer pelagic larval duration, and higher body condition than fish collected before winter. Lower settlement water temperatures were positively associated with winter survival, indicating that a settlement date closer to the onset of winter was favourable. Additionally, wintered fish, exhibited higher growth rates in early life compared to fish sampled prior to winter onset. These findings suggest that some early life history traits are selected for survival into winter, potentially mediating the physiological impacts of declining water temperature. If such traits increase overwinter survival they may facilitate the establishment of this range-expanding species in temperate rocky reef environments.

Faster larval growth and shorter pelagic duration enhance the post-settlement persistence of a common range-extending coral-reef fish in a temperate ecosystem

Climate-induced ocean warming facilitates the poleward range expansion of tropical marine species into temperate waters. Such tropicalisation is reshaping marine ecosystems globally and has ecological implications. Our understanding of the factors influencing the establishment and persistence of vagrant tropical species in temperate waters remains limited. To address this knowledge gap, we examined which early life history traits affect the post-settlement persistence of a vagrant tropical fish, the sergeant major damselfish Abudefduf vaigiensis, in temperate waters off southeast Australia. Over an 8-week period, fish were collected, and otolith microstructure analysis indicated that early post-settlement persistence was linked to fast larval growth in the week prior to settlement and to shorter pelagic larval duration, but not body size at hatching or body size at settlement. We conclude that successful invasions of temperate ecosystems by this vagrant tropical fish is likely mediated by demographic advantages these fish gain as early-stage larvae.

Evidence of growth-selective mortality of European anchovy larvae in the Bay of Biscay based on otolith microstructure analysis

Evidence of growth-selective mortality of European anchovy larvae in the Bay of Biscay based on otolith microstructure analysis

Comfort in stratification and trophic flexibility: argentine anchovy, Engraulis anchoita, larvae life traits in relation to their food sources

Comfort in stratification and trophic flexibility: argentine anchovy, Engraulis anchoita, larvae life traits in relation to their food sources

Estimating the occurrence of chum salmon Oncorhynchus keta of artificial origin on spawning grounds in the rivers and lakes of Iturup Island

Artificial reproduction of pacific salmon has been repeatedly criticized due to negative impact on natural populations. One of its aspects is replacement of wild spawners by spawners originated from hatchery on natural spawning grounds. This problem is relevant to Iturup Island, where the chum salmon stock is formed by both natural reproduction and artificial breeding. To evaluate their ratio, otolith marking of juveniles has been massively implemented at Iturup salmon hatcheries since 2009. The otoliths of chum salmon were collected for analysis from the spawning grounds in 6 rivers and lake-river systems of the Okhotsk Sea coast in the northern part of Iturup Island and at the slaughter point of salmon hatcheries from 2012 to 2022. Microstructure of otoliths from 8229 fish individuals, including 2709 specimens of сhum salmon, was examined to identify the tagged fish. The chum salmon of artificial origin were presented on all examined spawning grounds. Their number was calculated taking into account the percentage of tagged juveniles released from the hatcheries. Low level of straying was concluded for chum salmon on Iturup Island. Long-term dynamics of the ratio between wild and artificial spawners on spawning grounds was determined by changes in volume of juveniles release. Until 2014, the Reidovy and Kurilsky hatcheries released 50.106 chum juveniles annually, and the spawners of artificial origin were found sporadically on the spawning grounds in “wild” rivers. New fish hatcheries constructed after 2010 provided increase of their portion in 2014–2022 to 9.6–13.6 % on the spawning grounds unaffected to artificial reproduction and up to 93.3 % on the spawning grounds in the rivers with hatcheries. These high returns were supported by release of 74.4–191.8.106 juvenile fish annually. In the Reidovaya and Kurilka Rivers with a branched network of tributaries, the highest occurrence of artificial spawners was observed on the spawning grounds neighbored with hatcheries, whereas their portion decreased to 20 % on the spawning grounds in large tributaries of lower reaches; possibly, spawning grounds where the spawners of artificial origin are absent still exist in the basins of these rivers. Some increase of straying should be probably expected in future years because of huge amount of juvenile chum salmon released into the rivers of Prostor and Kurilsky Bays after 2020, at least 175.106 ind.

Fish Otolith Analysis in Southeast Asia: Expanding its Taxonomic Roots to More Ecological Targets

Otoliths, crucial tools for understanding fish biology and ecology, offer valuable insights into fisheries science in Southeast Asia. Traditionally used for age identification through shape analysis and growth ring counting, otolith studies have evolved to encompass broader ecological investigations. This review synthesizes literature on fish otoliths in Southeast Asia to identify research gaps and suggest future directions. Utilizing targeted keywords, we mined data from scientific search engines, focusing on peer-reviewed articles. Our analysis spans 1988 to 2021 and collated 129 publications, which were trimmed to 91 reviewed scientific articles. Otolith microstructure emerged as a primary research area of interest, with a focus on catadromous fishes from the Anguillidae family. Geographically, publications are concentrated in marine fish populations across archipelagic nations such as Indonesia, the Philippines, Malaysia, and the Vietnam Peninsula. Practical gaps, including validation precautions and cost-benefit analyses, potentially underscore the importance of methodological rigor and innovation in otolith research, but advances in mass-based age determination techniques and radiometric analysis present promising avenues for addressing these challenges. As global otolith research expands beyond aging studies, we urge fisheries scientists to explore innovative research areas outlined here to enhance their expertise in otolith microstructure and morphometric techniques. By integrating innovative approaches and multiple validation methods, researchers can enhance the reliability and accuracy of otolith-based age determination, ultimately advancing our understanding of fish population dynamics and supporting sustainable fisheries management practices in the Southeast Asian region.

Trophic level influences larval Shortbelly Rockfish development

Abstractr Objective Early life success of fishes is considered one of the most important drivers of recruitment to adult populations, and elucidating the governing mechanisms is important for management efforts. Many hypotheses over the past century have been proposed to explain recruitment fluctuation, with the recently postulated Trophic Efficiency in Early Life (TEEL) hypothesis arguing that a shorter food chain length equals greater energy transfer efficiency from primary producers to larval fishes, thereby reducing early-life mortality and ultimately leading to stronger recruitment. Under TEEL it would then be assumed that feeding low in the food chain would improve growth and body condition, as these are often shown to be associated with increased survival in larval fishes. The objective of this study was to test this aspect of the TEEL hypothesis by quantifying condition, growth, and trophic level of larval Shortbelly Rockfish Sebastes jordani collected by the California Cooperative Oceanic Fisheries Investigations program and archived at the Ichthyoplankton Collection. Methods The trophic level on larval Shortbelly Rockfish was assessed with compound-specific isotopic analysis of amino acids. Their size at age and survival were estimated with otolith microstructure. Their diet was examined through stomach content analysis. Result Observations indicate that larvae consuming prey at a lower trophic level have greater body weight and exhibit faster growth rates. However, feeding at a lower trophic level did not influence body length. The ingested prey responsible for the lower trophic level within larval rockfish could not be determined. Conclusion Larval Shortbelly Rockfish consuming prey at a lower trophic level garnered greater body weight and exhibited faster growth rates and provides support for the TEEL hypothesis. However, further research is needed to identify the preferred prey(s) responsible for the more efficient energy transfer.

Age Determination and Growth of Frigate Tuna (Auxis thazard, Lacepede, 1800) in the Celebes Sea

Frigate tuna (Auxis thazard, Lacepede, 1800) is a commercially valuable food fish thriving in tropical marine waters. In the Philippines, despite its abundance, information on its estimated age and growth patterns is lacking. This study reported the relationship between the size (fork length, FL) and age (otolith growth increment) of frigate tuna using the sagittal otoliths. Sampling was conducted in the Celebes Sea, including the inner bay and gulfs within it (e.g., Moro Gulf, Sarangani Bay, and Davao Gulf) from November 2020 to September 2022. A total of 1,046 frigate tuna samples with sizes ranging from 14.5 cmFL to 44.7 cmFL, caught using ring nets, hand lines, and purse seine nets, were examined. Results of the aggregated fish lengthweight relationship (R2 = 0.9819; a = 0.0068; b = 3.2632) indicated a strong positive allometric growth pattern. Similarly, a strong positive correlation (R2 = 0.7130) between the otolith length (n = 344) and fork length relationship indicates that the otolith increases in length as the fish grows. However, for the successfully aged otolith sections, only individuals collected in the western Celebes Sea (n = 113) demonstrated a good result covering ages ranging from one to four years old. From this information on the age-growth relationship, the von Bertalanffy growth function model generated the following values for L∞ at 62.1 cmFL and K at 1.0016/yr. The latter growth parameter estimates from otolith microstructure is the first record for frigate tuna derived from the age-length data.

Here to stay: evaluating establishment of eastern tubenose goby Proterorhinus semipellucidus (Kessler, 1877) in the Baltic Sea with otolith microchemistry and structure

In 2020, the presence of a novel non-indigenous species, eastern tubenose goby Proterorhinus semipellucidus (Kessler, 1877), was documented in the Gulf of Finland, Baltic Sea. As tubenose goby invasion may have a comprehensive ecological impact on the local ecosystem, it has to be confirmed whether the species has established an independently reproducing population or persists through continuous invasions in this area. We examined the otolith microstructure to determine the age of specimens sampled from the southern and northern coasts of the Gulf of Finland. Additionally, otolith microchemistry analysis was carried out on the southern coast specimens. Otolith microstructure revealed the population’s age structure, showing the presence of different age classes, including younger individuals. The microchemistry analyses suggested that the specimens had hatched in brackish water salinities similar to those found in the sampling areas. This indicates local reproduction instead of introduction from the virtually freshwater Neva Bay, which is most likely the donor area of the studied populations. These data confirm the establishment of a self-sustaining reproducing population of eastern tubenose goby in the Gulf of Finland, eastern part of the brackish Baltic Sea.

Migration patterns of the Japanese sardine in the Sea of Japan by combining the microscale stable isotope analysis of otoliths and an ocean data assimilation model

The Japanese sardine (Sardinops sagax melanostictus) is a small pelagic fish found in the Sea of Japan, the marginal sea of the western North Pacific. It is an important species for regional fisheries, but their dispersal and migration patterns during early life stages remain unclear. In this study, we analyzed the stable oxygen isotope ratios of otoliths of young-of-the-year (age 0) Japanese sardines collected from the northern offshore and southern coastal areas of the Sea of Japan in 2015 and 2016. The ontogenetic shifts of the geographic distribution were estimated by comparing the profiles of life-long isotope ratios and temporally varying isoscape, which was calculated using the temperature and salinity fields produced by an ocean data assimilation model. Individuals that were collected in the northern and southern areas hatched and stayed in the southern areas (west offshore of Kyushu) until late June, and thereafter, they can be distinguished into two groups: one that migrated northward at shallow layer and one that stayed around the southern area in the deep layer. A comparison of somatic growth trajectories of the two groups, which was reconstructed based on otolith microstructure analysis, suggested that individuals that migrated northward had significantly larger body lengths in late June than those that stayed in the southern area. These results indicate that young-of-the-year Japanese sardines that hatched in the southern area may have been forced to choose one of two strategies to avoid extremely high water temperatures within seasonal and geographical limits. These include migrating northward or moving to deeper layers. Our results indicate that the environmental variabilities in the southern area could critically impact sardine population dynamics in the Sea of Japan.

Growth–feeding linkage in small pelagic fish larvae in the Kii Channel, Japan

AbstractThe linkage between growth rate and feeding success has been shown to strengthen the effects of early growth rate on later growth rate in the early life history of fish. However, the growth–feeding linkage largely remains to be tested at the individual level within the same populations/cohorts. We examined the growth–feeding linkage for multiple populations/cohorts in Japanese anchovy Engraulis japonicus larvae and Pacific round herring Etrumeus micropus larvae, through otolith microstructure analysis, based on samples collected from the commercial fishery for larval fish in the Kii Channel, Japan. The three growth–feeding mechanisms, which are based on the respective potential advantages of larger somatic size, higher growth rate, and earlier morphological development for achieving feeding success, were tested to understand how growth rate relates to feeding success. The “somatic size” mechanism was supported for all of six samples for anchovy larvae and three of four samples for round herring larvae. The “growth rate” mechanism was supported for two of six samples for anchovy larvae and three of four samples for round herring larvae. The “morphological development” mechanism was supported for three of four samples for anchovy larvae and all of three samples for round herring larvae. Overall, the present analysis supported the growth–feeding linkage but revealed the dynamics of the growth–feeding mechanisms. All the mechanisms were shown to operate at least for certain populations/cohorts, but none of them were universally effective over all populations/cohorts across the two species. Understanding the dynamics of the growth–feeding mechanisms would provide precious hints for considering strategies of predicting recruitment dynamics.

Population connectivity of small yellow croaker (Larmichthys polyactis) in the southern Yellow Sea: Implications from multiple otolith-based approaches

Population connectivity of small yellow croaker (Larmichthys polyactis) in the southern Yellow Sea: Implications from multiple otolith-based approaches

Seasonal variability in the otolith and somatic size relationship of Japanese anchovy larvae: Counter effects of somatic growth and temperature

Seasonal variability in the otolith and somatic size relationship of Japanese anchovy larvae: Counter effects of somatic growth and temperature

Age and Growth of Japanese Anchovy (Engraulis japonicus, Temminck & Schlegel, 1846) in Coastal Waters around Shandong Peninsula, China

Japanese anchovy (Engraulis japonicus) is a small pelagic fish with commercial and ecological importance. In spite of its importance, in recent years, specific research on anchovy in the Shandong Peninsula area has been relatively scarce and outdated. This study aims to estimate the age and growth characteristics of anchovy through year-round seasonal sampling from 2016 to 2017, utilizing length–frequency and otolith microstructure analysis. The higher coastal abundance and larger size observed in the spring and summer suggest a potential peak spawning period for anchovies dominated by larger-sized individuals. Based on otolith analysis, anchovies range in age from 0 to 4 years, with a limited presence at age 0 and dominance in the age-1 group. The length–weight relationship (LWR) equation shows hyper-allometric growth for each season, with a mean relative condition factor (Kn) of 1.025 ± 0.005, indicating good health. Additionally, the von Bertalanffy growth equation of can be expressed as Lt = 154.40 [1 − e−0.604 (t + 0.965)], suggesting a medium growth rate (K = 0.604). These findings contribute to the understanding of anchovy age and growth patterns, emphasizing the continuous need for research and monitoring to support rational and sustainable fisheries management and conservation efforts.

Early growth and environmental conditions control partial migration of an estuarine-dependent fish

Partial migration is a widespread phenomenon in animals, whereby multiple groups follow different migration behaviors (i.e. contingents) within a single population. Fishes exhibit particularly high diversity in their early dispersal behaviors; however, whether these represent conditional partial migration behaviors remains unclear. We combined otolith microstructure and chemistry to assess the influence of early life conditions and environmental drivers on juvenile-stage partial migration of anadromous striped bass Morone saxatilis in the Hudson River (USA) in 2 consecutive years with contrasting hydrologic conditions. Time series clustering on otolith strontium (Sr) and barium (Ba) profiles revealed 4 dominant early migration contingents in both years: freshwater residents, oligohaline migrants, small mesohaline migrants, and large mesohaline migrants. In both years, juvenile partial migration appeared to be a conditional strategy linked to a growth-mediated threshold. The propensity to migrate early was related to slower larval growth, whereas freshwater residency and delayed migration were associated with faster larval growth. Differences in hatch dates may have indirectly affected migration contingents by exposing larvae to varying environmental conditions. In the dry year, dispersal timing to mesohaline habitats coincided with high freshwater flow and tidal currents, but not so in the higher-flow year. Recruitment to coastal nurseries outside the Hudson River occurred primarily during the juvenile phase. Early migration contingents could carry over to population dynamics, whereby diverse estuarine nursery habitats contribute differently to recruitment.

Post-settlement dynamics of Japanese flounder Paralichthys olivaceus in Tango Bay: Seasonal patterns in growth, mortality, and recruitment potential.

Japanese flounder Paralichthys olivaceus is one of the most valuable coastal flatfish species in East Asia. To investigate post-settlement growth and mortality, juveniles were sampled in Tango Bay (Japan) weekly throughout the settlement period in 2007 and 2008. Otolith (lapillus) microstructure analysis enabled the categorization of juveniles into six biweekly cohorts each year. Later cohorts exhibited higher growth rates possibly because of higher water temperatures. A key observation was the direct relationship between high mortality and high density in mid-season cohorts in both years, pointing to density-dependent mortality. This increased mortality may be attributed to predation, including cannibalism by earlier cohorts. Furthermore, growth-selective mortality was evident soon after settlement, underscoring the vulnerability of slow growers to predation during the early juvenile stage. Although earlier and later cohorts were less abundant but showed promising recruitment potential, the prospective contribution of mid-season cohorts to the adult population remained uncertain. The results clearly highlight the importance of density-dependent mortality in population regulation in post-settlement Japanese flounder.

Early life-history patterns in Patagonian toothfish Dissostichus eleginoides from the Patagonian Shelf

Many long-lived, deep-sea species of the higher latitudes possess protracted egg and larval phases leading to dispersal across large geographical areas. The timing of ontogenetic life-history shifts is vital for understanding dispersal potential, a key driver of spatial patterns and stock structure of Patagonian toothfish Dissostichus eleginoides on the Patagonian Shelf. The early life-history patterns from hatching until settlement into a demersal habitat remain elusive and largely unexplored. We applied a complementary approach using otolith microstructure and trace element analysis (by laser ablation-inductively coupled plasma mass spectrometry) to infer time-resolved elemental profiles that reflect the early ontogeny of age-0+ toothfish from key nursery areas on the Patagonian Shelf. Results revealed significant ontogenetic shifts across the early life history. Key biological benchmarks were identified, including (1) the hatch date distribution (predicted mean = 3 October ± 8.47 d); (2) a period of natal dispersal (0-50 d post hatch [dph]; 22 November); (3) entry of pelagic larvae onto the Patagonian shelf (50-100 dph; 1 January); (4) settlement into a demersal habitat (100-120 dph; 31 January); and (5) the start of a downslope ontogenetic migration along pathways to the continental slope (>120 dph). The results provide important considerations in terms of the complexity and protracted nature of early life-history stages in Patagonian toothfish as a complex process, informing future research objectives relating to the identification of the stock origin on the Patagonian Shelf.

Different growth patterns reveal the potential origins of two Pacific saury (Cololabis saira) groups in the northwest Pacific Ocean

Different growth patterns reveal the potential origins of two Pacific saury (Cololabis saira) groups in the northwest Pacific Ocean

Spawning cohort trade‐offs of reproductive time and output in cyprinid fish along an elevation gradient

AbstractUnderstanding environmental requirements for fish reproduction in natural habitats is crucial for population conservation and restoration. However, such information is extremely scarce for the highly threatened schizothoracine fishes that cover large elevation ranges on the Tibetan Plateau. This research investigated the spawning time, output and environmental conditions of wild Schizopygopsis thermalis along an elevational gradient (i.e., from 1766 to 4372 m) in the upper Nu‐Salween River. It found that the spawning grounds of S. thermalis were mainly located at elevations between 3600 and 4372 m, and spawning habitats mostly consist of still marginal areas (still water <10 cm deep) with gravel substrates. Otolith microstructure analysis revealed, for the first time, that S. thermalis spawns in two seasons (i.e., winter: from December to next February, and spring: from April to May), with the winter spawning period generally longer than the spring spawning period. Winter spawning started earlier and ended earlier at higher elevations, while spring spawning occurred earlier at lower elevations but ended simultaneously at higher elevations. As elevation increases, reproductive output also increases, and spawning cohorts shift from winter‐dominant to spring‐dominant. Winter spawning cohorts were associated with lower water temperatures but higher discharges than the spring spawning cohort, and both cohorts showed elevation‐related environmental preferences. Our results suggest that schizothoracine fish can adapt spawning strategies to elevation‐related environmental conditions, which fill the gaps in the reproductive characteristics of schizothoracine fishes, and highlight the importance of conserving schizothoracine habitats at high elevations in the Qinghai‐Tibetan rivers.

Temperature and prey density drive growth and otolith formation of the world's most valuable fish stock

Peruvian anchovy (Engraulis ringens) represents the largest single-species fishery worldwide. Knowledge on how temperature and prey availability influences growth and age estimation during marine fish early life stages is critical for predicting bottom-up processes impacting stock productivity under changing environmental conditions. We reared Peruvian anchovy larvae at two temperatures (14.5 and 18.5 °C) and prey concentrations [high (HF), and low (LF)] from 6 to 30 days post-hatch (dph) to measure growth rate and examine daily deposition of otolith increments. Peruvian anchovy larvae grew faster at 18.5 °C compared to 14.5 °C. Larvae reared at low prey concentration (18.5-LF) and low temperature (14.5-HF) grew 61 and 35% slower, respectively, than those at high prey and warm temperature (18.5-HF). Age and growth rates of larvae were well depicted in the otolith microstructure of well-fed larvae at 18.5 °C. However, larvae reared at 18.5-LF or 14.5-HF, had only 55 and 49% of the expected number of daily otolith increments. Our results suggest caution when attempting to explore how ocean processes regulate small pelagic stocks, the productivity of which are largely driven by changes in the survival and growth of young larvae.