Migratory history of Rhinogobius sp. OR morphotype “Shimahire” as revealed by otolith Sr:Ca ratios

The migratory history of the Rhinogobius sp. OR morphotype “Shimahire” collected from a slower current environment in the Maruyama River, the Ibo River, and the Kako River, Japan, was studied by examining the strontium and calcium concentrations in the otoliths. The otolith Sr:Ca ratios of almost all samples showed consistently low ratios from the core to the edge, reflecting the fact that the organisms had been living in a freshwater environment their entire lives. The ratios of Rhinogobius sp. CB and Rhinogobius flumineus living in the sympatric habitats with the Rhinogobius sp. OR morphotype “Shimahire” in the Kako River showed an amphidromous and fluvial life cycle, respectively. These findings suggest that the Rhinogobius sp. OR morphotype “Shimahire” has a freshwater resident life cycle.     

Coloration and ontogenetic features of fluviatile species of <Emphasis Type="Italic">Rhinogobius</Emphasis> (Gobioidei: Gobiidae) in Amami-oshima Island,Ryukyu Islands,Japan

 The fluviatile Rhinogobius sp. 1 (hereinafter R. sp. 1) (Japanese name kibara-yoshinobori or English name yellow belly medium-egg type) is broadly distributed in the Ryukyu Islands ranging from Amami-oshima Island to Iriomote Island. However, based on the molecular evidence, this species has probably had multiple origins from amphidromous species. We compared the coloration of specimens at Amami-oshima I. with that of the other specimens (islands) in the Ryukyu Is. Amami-oshima I. specimens of R. sp. 1 were different from the specimens of other populations in having five to six cross lines on the caudal fin. We examined the early life history of fluviatile Rhinogobius at Amami-oshima I., based on rearing experiments, and estimated the age of wild specimens by counting otolith increments. Spawned egg capsules of “Rhinogobius sp. 1” at Amami-oshima I. were larger than those of amphidromous species. Their developmental stage in newly hatched larvae was similar to that of Okinawan R. sp. 1 in having a straight notochord; however, it had a flexed notochord earlier than that of Rhinogobius sp. 2 (hereinafter R. sp. 2) (aobara-yoshinobori or blue belly medium-egg type). The ontogenetic trajectory of “Rhinogobius sp. 1” in Amami-oshima I. was similar to Okinawan R. sp. 1 (30 days in larval duration) but different from R. sp. 2 (15 days). In amphidromous relatives of R. sp. 2, developmental timing during larval period was earlier than in the amphidromous relatives of R. sp. 1. It has been suggested that the phenomenon of fluvial landlocking has been accompanied somewhat by egg size increase (on the basis of a few examples). However, the ontogenetic trajectories of fluviatile Rhinogobius species may be a reflection of those of ancestral amphidromous species. Received: March 18, 2002 / Revised: November 7, 2002 / Accepted: December 10, 2002     

Diverse migratory histories in a brackish water type of the ninespine stickleback, <Emphasis Type="Italic">Pungitius pungitius</Emphasis>

The life history in a brackish water type of the ninespine stickleback, Pungitius pungitius, was studied by examining the strontium (Sr) and calcium (Ca) concentrations in the otoliths. The fluctuating patterns of Sr/Ca ratios along the life history transect in the otoliths varied widely among fish in spite of their identification as brackish water type as estimated by morphological characteristics. More than 70% fish showed the intermediate otolith Sr/Ca ratio throughout, averaging 5.23–7.71 × 10⁻³. Besides this brackish water resident life history type of P. pungitius, other sticklebacks had anadromous (25%) and freshwater amphidromous (2.5%) life history types. These findings clearly indicate that the migration of the ninespine stickleback between fresh and sea waters is obligatory but facultative having an ability to utilize the full range of salinity in its life history.     

Flexible Life History Strategies of Ninespine Sticklebacks,Genus <Emphasis Type="BoldItalic">Pungitius</Emphasis>

Synopsis We studied the life histories of the ninespine sticklebacks, Pungitius pungitius and Pungitius tymensis, collected from Japanese freshwater and brackish (sea) water habitats by examining the strontium (Sr) and calcium (Ca) concentrations in their otoliths. The Sr:Ca ratios in the otoliths changed with the salinity of the habitat regardless of identification as freshwater or brackish water type based on morphological characteristics. The ninespine sticklebacks living in a freshwater environment showed consistently low Sr:Ca ratios throughout the otolith. These samples were identified as a standard freshwater type. In contrast, all freshwater-type fishes collected from the intertidal zone showed higher otolith Sr:Ca ratios than those in the standard freshwater type, and the ratios fluctuated with the growth phase. All brackish water-type fishes collected in the intertidal zone showed the highest otolith Sr:Ca ratio throughout the otolith. In the present study, besides the two representative life history types of P. pungitius, i.e., freshwater and brackish water life history types, other sticklebacks had an anadromous life history type. These findings clearly indicate that the ninespine stickleback has a flexible migration strategy with a high degree of behavioral plasticity and an ability to utilize the full range of salinity in its life history.     

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.     

Migration flexibility between freshwater and marine habitats of the pond smelt Hypomesus nipponensis

The life histories of the pond smelt Hypomesus nipponensis collected from Japanese fresh waters and brackish (sea) waters were studied by examining the strontium (Sr) and calcium (Ca) concentrations in their otoliths. The Sr:Ca ratios in the otoliths changed with the salinity of the habitat. The pond smelt living in a freshwater environment showed consistently low Sr:Ca ratios throughout the otolith, averaging 1·2–1·3 × 10⁻³. These samples 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 addition to the two representative life‐history types of H. nipponensis , i. e . freshwater and anadromous life‐history types, other pond smelts were found to have an estuarine resident life history‐type with no freshwater phase, indicating that the pond smelt has a flexible migration strategy with a high degree of behavioural plasticity and an ability to utilize the full range of salinity in its life history.     

Migratory histories of three types of Cottus pollux (small-egg, middle-egg, and large-egg types) as revealed by otolith microchemistry

 Migratory histories of three types of Cottus pollux, the small-egg type (SE type), middle-egg type (ME type), and large-egg type (LE type), were studied by examining strontium (Sr) and calcium (Ca) in their otoliths with wavelength dispersive X-ray spectrometry on an electron microprobe. The Sr : Ca ratios in the otoliths changed both with ontogenetic development and with salinity of the habitat. Otolith Sr : Ca ratios of LE-type samples and the ME-type samples from the Honmyo River, Kyushu Island, showed consistently low ratios, averaging 1.8 × 10⁻³ and 2.4 × 10⁻³ from the core to the edge, respectively. In contrast, otolith Sr : Ca ratios of SE-type samples and the other four ME-type samples from Hokkaido and Honshu Islands fluctuated strongly along the life history transects in accordance with migration patterns from freshwater to the sea and vice versa. The otolith Sr : Ca ratios of SE-type samples showed low ratios from the core to a point around 15 μm, averaging 1.5 × 10⁻³, and subsequently increased sharply with a high Sr : Ca ratio phase to a point around 400 μm, averaging 5.5 × 10⁻³, and followed again a low ratio phase to the edge with averages of 3.1 × 10⁻³. Similar fluctuation patterns in otolith Sr : Ca ratios were found for the four ME-type samples. These findings clearly demonstrated that otolith Sr : Ca ratios reflected the sculpin's life histories, as being fluvial for the LE type and the Honmyo River ME type and amphidromous for the SE type and the other four populations of ME type. Received: August 1, 2002 / Revised: October 15, 2002 / Accepted: October 28, 2002 Acknowledgments We thank Dr. N. Miyazaki, University of Tokyo, for his kind guidance of our joint research. Thanks are also offered to Drs. H. Sakai, National Fisheries University, Y. Yamazaki, Toyama University, and R. Yokoyama, Hokkaido University, and Mrs. N. Okabe and Y. Suzuki of Yamagata Prefecture for their help in sample collection. This work was partly supported by a Grant-in-Aid (No. 13660171) from the Japan Ministry of Education, Science, Sports and Culture to A. Goto. Correspondence to:Akira Goto     

Migratory flexibility in native Hawai'ian amphidromous fishes

We assessed the prevalence of life history variation across four of the five native amphidromous Hawai'ian gobioids to determine whether some or all exhibit evidence of partial migration. Analysis of otolith Sr.: Ca concentrations affirmed that all are amphidromous and revealed evidence of partial migration in three of the four species. We found that 25% of Lentipes concolor (n = 8), 40% of Eleotris sandwicensis (n = 20) and 29% of Stenogobius hawaiiensis (n = 24) did not exhibit a migratory life-history. In contrast, all individuals of Sicyopterus stimpsoni (n = 55) included in the study went to sea as larvae. Lentipes concolor exhibited the shortest mean larval duration (LD) at 87 days, successively followed by E. sandwicensis (mean LD = 102 days), S. hawaiiensis (mean LD = 114 days) and S. stimpsoni (mean LD = 120 days). These findings offer a fresh perspective on migratory life histories that can help improve efforts to conserve and protect all of these and other at-risk amphidromous species that are subject to escalating anthropogenic pressures in both freshwater and marine environments.     

Migratory history of the spotted flagtail, <Emphasis Type="Italic">Kuhlia marginata</Emphasis>

The spotted flagtail, Kuhlia marginata (Kuhliidae) is commonly found in streams throughout the Ryukyu Archipelago, including Okinawa Island, Japan. Although it has been suggested that they spawn at sea, little is known about their migratory history. The aim of the study was to clarify their migration history based on otolith microchemistry analysis, size composition and the gonadal development of fish collected from the Genka River on Okinawa Island. All strontium/calcium (Sr/Ca) ratios of otoliths remained high around their cores, and then dropped rapidly at some distance from the core. The estimated standard length corresponding to decreases correlated with the size of new recruits collected in the river (ca. 20 mm in standard length: SL). Multiple increases, the sign for migrations into the high saline area, were recognized intermittently around the otolith margin. As the estimated SL at these increases in the Sr/Ca ratio occurred above the minimum maturation size (female: 95.5 mm SL; male: 83.5 mm SL), such multiple increases in Sr/Ca ratios were caused by spawning migration. Therefore, we conclude that the catadromous pattern of K. marginata is as follows; this species grows in the sea during the early life stage until ca. 20 mm SL and then grow in the freshwater area until maturation, before they migrate again to the sea for spawning. Sr/Ca ratio profiles also suggested that a large number of males did not return to the freshwater area after spawning, whereas females might spawn several times during their lives around the inshore area.     

Diversity of life strategies of pikepech <Emphasis Type="Italic">Sander lucioperca</Emphasis> (L.) in the Lower Volga (by the data of microelement composition of otolithes)

Strontium (Sr) and calcium (Ca) contents and Sr/Ca ratios in otoliths of pikeperch Sander lucioperca have been studied by X-ray fluorescent microanalysis. A sample of 95 specimens from the Lower Volga region are studied. The fish were obtained in a section of the Akhtuba River at a distance of 250–279 km upstream from the Caspian Sea. Some specimens in the sample have low strontium content throughout the otolith. The other fish have increased both Sr content and Sr/Ca ratios in core zones of otolith or near its outer edge: the Sr/Ca ratio is over 6.00 × 10^–3, with a maximum at 10.02 × 10^–3. The fish with a low Sr/Ca ratio live in freshwater and demonstrate a resident life history strategy. Pikeperch that have increased ratios of Sr/Ca in outer zones of otolith demonstrate a migratory life history strategy. These fish leave the freshwater of the Volga and feed in brackish water of the Northern Caspian Sea. Some migratory fish migrate to the sea as underyearlings, stay in a brackish water for 1 year or less, and then return back to fresh water for the rest of its life. The other group migrates back and forth from freshwater to the sea several times during their life. Finally, some fish leave freshwater for 1–2 years, spending this time in the Northern Caspian Sea. The conclusion is that the pikeperch stock in the Lower Volga has a complicated composition and consists of freshwater (residents and rheodromic ones) and migratory (anadromous and semianadromous) fish.     

A new lentic form of the “yoshinobori” species complex, Rhinogobius spp. from Lake Biwa, Japan, compared with lake–river migrating Rhinogobius sp. OR

 The various life history strategies seen within the “yoshinobori” species complex of the genus Rhinogobius, which differentiated from an amphidromous ancestor, have been grouped ecologically into amphidromous, fluvial, and lacustrine types. In the Lake Biwa water system, two lacustrine forms exist, a newly discovered, exclusively lentic form and the already well known Rhinogobius sp. OR, which generally undergoes lake–river migration but also includes lentic individuals that share spawning grounds with the former lentic form. Detailed morphological comparisons and allozyme analysis revealed consistently clear differences between the two forms, indicating them to be distinct species. The newly discovered lentic form has many distinctive morphological features that enable it to be distinguished from sympatric Rhinogobius sp. OR: dwarfness, short snout, longitudinally slender pelvic fin, undeveloped frenum with a low lamella, low first dorsal fin in adult males, lesser caudal peduncle depth, scaleless predorsal and ventral areas, and incomplete sensory canals. The lentic form was temporarily named Rhinogobius sp. BW. The life history patterns of the lake-inhabiting populations were separated into two categories: a lake–river migratory lifestyle and an exclusively lentic lifestyle.     

Differences in the Trace Element Deposition in Otoliths Between Marine- and Freshwater-resident Japanese Eels, Anguilla japonica, as Determined by Laser Ablation ICPMS

Synopsis In order to determine whether the trace element composition in otolith of the Japanese eel Anguilla japonica could be used to determine its habitat use, we used laser ablation inductivity coupled plasma mass spectrometry (LA-ICPMS) to assay sectioned otoliths of both marine-resident (sea eels) and freshwater-resident (river eels) eels. A close linear relationship in the Sr:Ca ratios between EPMA (X-ray analysis with an electron microprobe) and LA-ICPMS analyses was found, suggesting that the latter technique could be used to separate the marine and freshwater life phases. Elemental signatures in the otolith outside the elver mark showed significant differences in Cr:Ca, Mn:Ca, and Ba:Ca ratios as well as Sr:Ca ratios between sea and river eels. These results indicate that the elemental compositions may reflect environmental variability between marine and fresh water masses. Thus, those elemental ratios determined by LA-ICPMS analysis seem to have the potential to help distinguish the habitat of the eel.     

Occurrence of the non-anadromous life history in the shirauo, Salangichthys microdon

Strontium (Sr) and calcium (Ca) concentrations in the otoliths of the shirauo, Salangichthys microdon, collected from Japanese coastal waters were examined by wavelength‐dispersive X‐ray spectrometry on an electron microprobe. The otolith Sr : Ca ratios gradually increased from 15.7?19.7 × 10^?3 around the core to 32.8?39.4 × 10^?3 around the edge of otoliths, with no transition point from the low Sr : Ca ratio phase to the high phase. The fluctuation pattern of otolith Sr : Ca ratios was different from the anadromous form reported in a previous study. The evidence indicates that the fish do not necessarily migrate into freshwater during the growth phase.     

Otolith Sr:Ca ratios of freshwater goby Rhinogobius sp. TO indicating absence of sea migrating traits

The strontium and calcium concentration ratios in the otoliths of Rhinogobius sp. TO collected from the river flowing from a pond of Aichi Expo Park, a waterway from the Yahagi and Kushida Rivers and the Yahagifuru River, Japan, were studied to confirm the presence or absence of sea migrating traits during the larval period. The ratios of all samples showed consistently low ratios from the core to the edge, suggesting that the Rhinogobius sp. TO has a freshwater resident lifestyle. Therefore, conservation of river ecosystems is essential to protect the natural populations of this goby.     

Migratory history of the threespine stickleback Gasterosteus aculeatus

 The migratory history of two highly divergent forms (the Japan Sea and Pacific Ocean forms) of the threespine stickleback Gasterosteus aculeatus collected from Japanese brackish water (seawater) and freshwater was 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 otolith Sr : Ca ratios of the freshwater resident-type samples of the Pacific Ocean form showed consistently low Sr : Ca ratios, averaging 0.85–0.96 × 10⁻³ from the core to the edge. In contrast, the otolith Sr : Ca ratios of the anadromous type of both the Japan Sea and Pacific Ocean forms fluctuated strongly along the life history transects in accordance with their migration patterns from seawater to freshwater. The higher ratios in the anadromous type, averaging 5.4 × 10⁻³, in the otolith region from the core to 200 μm, corresponded to the seagoing period, suggesting that otolith Sr : Ca ratios are affected by ambient water salinity. These findings clearly indicate that otolith Sr : Ca ratios reflect individual life histories, and that these two highly divergent forms of stickleback have a flexible migration strategy. Received: May 23, 2002 / Revised: July 29, 2002 / Accepted: August 19, 2002 Acknowledgments We are grateful to Dr. S. Mori of Gifu Keizai University, and Miss M. Yamada and Messrs. M. Kume and T. Kitamura of Hokkaido University, for their assistance in sampling. This work was supported in part by Grant-in-Aid No. 13760138 from the Ministry of Education, Culture, Sports, Science and Technology, Japan. Correspondence to:Takaomi Arai     

Effects of salinity on strontium:calcium ratios in the otoliths of the West African black-chinned tilapia Sarotherodon melanotheron in a hypersaline estuary

The biology and the behaviour of fish populations in hypersaline environments are poorly known. The habitat occupation strategy of the tilapia Sarotherodon melanotheron has been studied along a salinity gradient in the Saloum hypersaline estuary in Senegal (salinity between 32 and 100). The individual migratory behaviour has been analysed from otolith strontium-to-calcium concentration ratios from fish sampled in five locations during the 2003 wet season and the 2004 dry season. In the upper part of the estuary (salinities > 50), the Sr:Ca ratio in the otolith showed high variations, from 2.51 to 33.30 × 10⁻³. These maximum observed values have never been reported in the literature. The individual mean of Sr:Ca ratios increased according to the salinity gradient in the estuary, with significantly higher values in the upper part (Sr:Ca mean = 16 × 10⁻³) than in the lower part (salinity < 50, Sr:Ca mean = 12 × 10⁻³). No significant difference in the Sr:Ca mean was observed between locations with comparable salinities. Sr concentration in the water at the different locations was positively correlated with ambient salinity. The mean of Sr:Ca in the otoliths was then in relationship with the level of Sr in the water. Thus, the Sr:Ca ratios in the otolith of S. melanotheron allowed to discriminate the populations of this species and to hypothesize that they did not undertake large scale movements within the estuary.     

Application of otolith microchemistry to estimate the migratory history of Japanese eel Anguilla japonica on the Sanriku Coast of Japan

The age and migratory history of the Japanese eel, Anguilla japonica Temminck & Schlegel, collected in Miyako Bay along the Sanriku coast of Japan, was examined using the otolith microstructure and analysis of strontium (Sr) and calcium (Ca) concentrations conducted with wavelength dispersive X‐ray spectrometry by an electron microprobe. The line analysis of Sr : Ca ratios along the life history transect of each otolith showed a peak (ca. 15–17 × 10^?3) which corresponded with the period of their leptocephalus and early glass eel stages in the ocean. The mean Sr : Ca ratios from the elver mark to the otolith edge indicated that there were eels with several general categories of migratory history, including sea eels that never entered freshwater (average Sr : Ca ratios, ≥6.0 × 10^?3), and others that entered freshwater for brief periods but returned to the estuary or bay. This evidence of the occurrence of sea eels in this northern area indicates that Japanese eels of the Sanriku coast do not necessarily migrate into freshwater rivers during recruitment as do glass eels at the beginning of their growth phase; even those that do enter freshwater may later return to the marine environment. Thus, anguillid eel migrations into freshwater are clearly not an obligatory migratory pathway, but rather a facultative catadromy with seawater or estuarine residents as an ecophenotype.     

Asteriscus v. lapillus: comparing the chemistry of two otolith types and their ability to delineate riverine populations of common carp Cyprinus carpio

The chemical composition of common carp Cyprinus carpio asteriscus (vaterite) and lapillus (aragonite) otoliths from the same individual and reflecting the same growth period was measured to (1) determine whether there are differences in the uptake of trace metals (Mg:Ca, Mn:Ca, Sr:Ca and Ba:Ca ) and Sr isotope ratios (⁸⁷Sr:⁸⁶Sr) in co‐precipitating lapilli and asterisci and (2) compare the ability of multi‐element and isotopic signatures from lapilli, asterisci and both otolith types combined to discriminate C. carpio populations over a large spatial scale within a river basin. Depth profile analyses at the otolith edge using laser‐ablation inductively coupled plasma mass spectrometry showed that asterisci were enriched in Mg and Mn and depleted in Sr and Ba relative to lapilli, whilst ⁸⁷Sr:⁸⁶Sr values were nearly identical in both otolith types. Significant spatial differences among capture locations were found when all trace element and Sr isotope ratio data were aggregated into a multi‐element and isotopic signature, regardless of which otolith type was used or if they were used in combination. Discriminatory power was enhanced, however, when data for both otolith types were combined, suggesting that analysis of multiple otolith types may be useful for studies attempting to delineate C. carpio populations at finer spatial or temporal scales.     

Factors influencing Sr/Ca ratios in otoliths of Girella elevata: an experimental investigation

The utility of Sr/Ca ratios in otoliths as indicators of thermal history in fish was investigated for juvenile Girella elevata . There was no direct relationship between ratios of Sr/Ca and temperature of the water, as has been assumed in many previous studies. Sr/Ca ratios did not decrease when water temperature was elevated from 19 to 28° C. Elevation of ambient Sr levels in the sea water caused a significant increase in Sr/Ca ratios in otoliths, and there was a detectable increase in Sr/Ca ratios in otoliths of some individuals fed an Sr-enriched diet. Multiple factors may influence natural Sr/Ca ratios in otoliths of juvenile G. elevata and their interactions make it difficult to interpret the chronology of conditions experienced by an individual fish during early life in the pelagic or benthic environment.     

Strontium:cakium concentration ratios in otoliths of herring larvae as indicators of environmental histories

Synopsis Elemental analyses, using wave-length dispersive electron microprobe techniques on otoliths from reared Atlantic herring larvae, Clupea harengus, showed trace quantities of strontium relative to that of calcium, and an inverse relationship between Sr/Ca concentration ratios and rearing temperature. These data are consistent with those for coral aragonite, in that there appears to be an inverse temperature effect on physiological incorporation of strontium in the otolith aragonite. Our determinations of Sr/Ca concentration ratios of lab-reared herring larvae showed that the deposition of strontium relative to calcium and the rearing temperature were related, where: T (° C) = −2.955 [Sr/Ca] × 1000 ± 19.172. This principle thus makes it possible to use Sr/Ca concentration ratios in fish otoliths to delineate past temperatures experienced by an individual. Further, combining electron microprobe analyses with scanning electron microscope (SEM) examinations of daily increments in the same otolith makes it possible to reconstruct the temperature history for an individual fish on a time scale of days. An example of the application of the technique to an approximately six-month-old field-caught herring larva is given, and the limitations of the technique are discussed.