Population structure of the black seabream Spondyliosoma cantharus along the south-west Portuguese coast inferred from otolith chemistry

The chemistry of black seabream Spondyliosoma cantharus otoliths from three main fishery grounds (Olhão, Sagres and Sesimbra) located along c. 400 km of the Portuguese south and west coasts was examined. Element:Ca ratios were determined in whole otoliths and otolith cores of young adult specimens of 2–3 years of age. Using the data from whole otoliths, it was possible to discriminate among S. cantharus from the three fishing grounds with an average accuracy of 91%. Differences among fishing grounds were significant for all element:Ca ratios, and otoliths from Sagres had significantly higher levels of all ratios compared to the other fishing grounds. In contrast, the chemical composition of the otolith core, representative of the larval stage, showed limited variation among the fishing grounds, with an average discrimination accuracy of only 44%, although the Mg:Ca ratio of the otolith cores was also significantly higher for the Sagres samples. The data suggest that larval stages experienced a homogenous environment consistent with an offshore oceanic spawning. Juveniles appeared to display local residency on the inshore fishing grounds, areas probably characterized by greater environmental heterogeneity. Spondyliosoma cantharus population structure is consistent with distinct local population units that share a spawning ground providing recruits to different coastal fishery areas.     

Age and growth of Anguilla bicolor bicolor leptocephali in the eastern Indian Ocean

A sampling survey for leptocephali was conducted in the eastern Indian Ocean to the west of Sumatra from 5 to 20 June 2003 in an overlapping area with the historical survey in September to November 1929 during the Danish Round the World Expedition. The age and larval growth rate of 34 Anguilla bicolor bicolor collected in 2003 were estimated using their otolith microstructure to obtain new information about the early life history of this sub-species. The total lengths and ages of these leptocephali were 44·1–55·5 mm and 114–158 days, respectively. Their hatching dates ranged from 3 January to 20 February 2003. Combining these age data and the estimated age of leptocephali collected by others in the same area, this sub-species was estimated to have a wide range of spawning periods. Individual growth rates of the leptocephali in 2003 ranged from 0·32 to 0·39 mm day⁻¹ with a mean ± s . d . of 0·35 ± 0·02 mm day⁻¹. These values were lower than the growth rates of leptocephali of other tropical eels such as Anguilla celebesensis or Anguilla borneensis , suggesting that A. b. bicolor from the eastern Indian Ocean have a longer leptocephalus period of oceanic migration.     

Nutritional dynamics during the development of xylophagous beetles related to changes in the stoichiometry of 11 elements

The present study examines the adaptive strategy used by wood‐boring beetles to compensate for the lack of nutrients in dead wood. The contents of nutritional elements in growing wood‐boring beetles (Stictoleptura rubra L. and Chalcophora mariana Dejean) are compared with the elemental composition of decaying dead wood (pine stumps), showing changes during the beetles' ontogenetic (i.e. larval) development. The stoichiometric ratios of C and other nutritional elements (N, P, K, Na, Ca, Mg, Fe, Zn, Mn and Cu) are investigated to identify the most important nutrients for larval development. The degree of nutritional mismatch that is encountered by the beetle larvae changes dramatically over 3–4 years of simultaneous larval growth and wood decay. Excluding C, the relative contents of nutritional elements increase substantially in decaying wood, whereas the opposite tendency is found in larvae, most likely because of carbon deposition in fat. The elements limiting larval development because of their scarcity in dead wood are N, P, K, Na, Mg, Zn and Cu. Fungal activity (i.e. the transport of nutrients from the surrounding environment to decaying stumps) can explain the observed mitigation of the original mismatch, although prolongation of the larval development time is still necessary to compensate for the scarcity of some of the required elements in food.     

Segregation of SE Pacific and SW Atlantic southern blue whiting stocks: integrating evidence from complementary otolith microchemistry and parasite assemblage approaches

Southern blue whiting Micromesistius australis support one of the largest industrial fisheries in South America. Two main spawning/nursery grounds are known: one in the SW Atlantic Ocean (SWA), southwest from the Falkland (Malvinas) Islands; and other in the SE Pacific Ocean (SEP), south from the Taitao Peninsula. Juveniles originating from both grounds are believed to mix during migration and/or in feeding areas in the Scotia Sea. Previous efforts to distinguish stocks in this area have yielded contradictory results between genetics and otolith microchemical analyses. In the present work we revisited the null hypothesis of a single stock occurring in the broader SWA-SEP region by comparing and integrating results from different approaches: trace metals (Ca, Sr, Ba, Mg, Mn) and stable isotopes (δ¹³C, δ¹⁸O) in otolith cores, and parasite assemblage compositions in adults from SWA and SEP spawning grounds. We found significant differences in Sr:Ca, δ¹³C and δ¹⁸O mean ratios between spawning grounds. The best trace element discriminant model classified 83% of the samples. Each stable isotope discriminated >90% of the samples, while combining them into a bivariate discriminant model led to 100% classification success. Higher δ¹⁸O levels in the SWA samples agreed with lower mean temperature and higher ambient δ¹⁸O levels in that area. Parasite assemblage compositions also showed significant differences between grounds regarding the prevalence of Chondracanthus, Contracaecum, Hepatoxylon and Grillotia and the abundance of Diclidophora, Anisakis, Contracaecum, Hysterothylacium and Hepatoxylon. Parasite-based discriminant models supported 90–100% correct assignment of samples to capture location. Although preliminary due to limited sampling coverage, our results support the existence of at least two ecologically distinct sub-populations of southern blue whiting in South America. The joint use of otolith microchemistry and parasitological techniques showed to be a promising way to test hypotheses concerning ecological stocks in marine fishes.     

Otolith elemental fingerprints of juvenile Pacific swordfish Xiphias gladius

The trace element composition of young‐of‐the‐year (YOY) juvenile swordfish Xiphias gladius sagittal otoliths were analysed as a preliminary test of the value of otolith elemental fingerprints for determining swordfish nursery ground origins in the central Pacific Ocean. A suite of five elements (Mg, Zn, Sr, Ba and Pb) was assayed with isotope dilution ICP‐MS; all elemental concentrations were roughly comparable to otoliths of other marine fishes. Multivariate analyses of elemental fingerprints based on Ba and Sr revealed differences between sample sites, and the magnitude of the differences increased with latitudinal separation. With more comprehensive sampling of nursery grounds, it should be possible to identify origin of nursery ground for adult swordfish by analysing the YOY juvenile portion of the sagittal otolith.     

Retracing migration pattern in reproductive and non-reproductive female kutum Rutilus frisii,in south Caspian Sea,using otolith microchemistry

Because trace elements of otoliths are considered a natural marker capable of recognizing the chemical composition of ambient water and fish migration history, these elements could be potentially used to analyse the movement of reproductive (R) and non-reproductive (NR) mature-sized fish. Supposedly, it is not essential for NR individuals to migrate to rivers for spawning because they do not have developed gonads. To investigate the potential differences in migration history between female R and NR kutum, Rutilus frisii, in the southwest waters of the Caspian Sea, the ratios of Sr, Ba, Mg, Na, K and P to Ca in otoliths (from the core to the edge) were examined using laser ablation–inductively coupled plasma–mass spectrometry. In NR fish, a significant increase in Sr:Ca ratio in the otoliths' growth rings, likely due to greater seawater residency, and an increase in Ba:Ca ratio in the last two rings were observed. Increased Ba:Ca ratio could be due to the movement of NR mature-sized fish to the coastal zones for foraging. Seasonal physiological factors such as gonad maturation and spawning activity are more likely to be involved in differences in the other elemental ratios (Mg, Na, K and P). These results suggest that microchemical analyses of growth rings of otolith can be used as a valuable tool for better understanding the movement pattern of different types of adult fish, which could be completed with data from other methods like tagging.     

Growth and morphological development of sagittal otoliths of larval and early juvenile Trachurus japonicus

The daily periodicity of growth increment formation in sagittal otoliths of jack mackerel Trachurus japonicus was validated by marking otoliths with alizarin complexone (ALC). Analysis of otoliths of known‐age juveniles confirmed that the first increment formed on day 3 after hatching, and was associated with first feeding. A total of 198 specimens, ranging from 2·6 to 49·2 mm in body length (notochord length or standard length) and from 7 to 78 days in age, were collected in the East China Sea and Tosa Bay, and used to examine the association between otolith morphological development and ontogenetic development. The relationship between body length ( L ) and otolith radius ( R ) was significantly described by the linear function L  = 2·65 + 0·0425 R ( n  = 198, r ² = 0·99, P  < 0·001), indicating that somatic growth history can be reconstructed from otolith growth patterns. The otolith was primarily spherical in the preflexion larval stage, and became elongated with notochord flexion. The first secondary primordium formed at c . 25 days, during the middle postflexion stage, and was associated with metamorphosis. By c . 42 days the sagittal otolith was adult‐like in morphology, with the primary growth zone enclosed by the marginal growth zone, except in the anterior rostrum area. Thus age, growth and developmental stages were recorded in sagittal otoliths during the larval and early juvenile stages of jack mackerel.     

The detection of elements in larval otoliths from Atlantic herring using laser ablation ICP-MS

Trace element concentrations of otoliths from larval herring Clupea harengus collected from known spawning beds in the Celtic and Irish Seas, were investigated using laser ablation ICP-MS and compared with concentrations in the larval cores of juvenile otoliths from the same populations and year class. A range of elements (Mg, Zn, Sr, Ba and Pb) was detectable in early larval otoliths (20–40 µm diameter). Larval otolith concentrations exceeded the larval core concentrations of juvenile otoliths and also the concentrations reported in the literature, for Mg, Zn, Ba and Pb, indicating that the measurement of elements in larval otoliths was severely affected by post-mortem contamination, most likely due to adherence of tissue and endolymph residue on the otolith surface. Comparison of otolith composition between larvae from two freezing treatments showed that contamination from Mg and Zn was more serious in otoliths that had remained in frozen larvae for prolonged periods. Larval populations from the two seas showed significant differences in otolith Sr concentrations, which were consistent over two sampling years. Similar differences were seen in the corresponding juvenile populations. The results show that while early larval otoliths are extremely susceptible post-mortem contamination, Sr concentrations can be reliably measured using laser ablation ICP-MS and for this element, the detection of region specific differences is possible.     

Clues to the location of the spawning area and larval migration characteristics of Anguilla mossambica as inferred from otolith microstructural analyses

The spawning area location and the larval migration characteristics of Anguilla mossambica were studied through the examination of early life-history traits (ELHT) inferred from otolith microstructural analyses of 122 glass A. mossambica collected along the eastern coast of Madagascar, in the south-western Indian Ocean. Backcalculated hatching dates of leptocephali that recruited between November 2005 and February 2006 suggested that spawning was continuous from June to November 2005, although individual migration duration periods were variable. Larvae that exhibited the highest daily otolith growth rates had the shortest leptocephalus durations and total length ( L _T) at recruitment, possibly because they reached the competence to metamorphose more rapidly and to recruit to fresh waters. Migration durations and L _T increased from north to south on the Malagasy eastern coast, supporting earlier suggestions that A. mossambica spawns north-east of Madagascar, west of the Mascarene Ridge in the Indian Ocean.     

The effect of otolith storage methods on the concentrations of elements detected by laser-ablation ICPMS

Otoliths of male (1+ year old) Terubok, tropical shad Tenualosa toli from the Lupar River, Sarawak, were treated in different ways to assess the effect of post-capture storage on element concentrations in the otolith core and edge detected by laser-ablation inductively coupled plasma mass spectrometry (ICPMS). Five treatments were compared: rapid removal and dry storage; fish kept 5 h after capture then otoliths removed; rapid removal and stored in alcohol; fish rozen for 24 h then otoliths removed; and storage of intact head in alcohol for several weeks. Seven elements were detected at the core and edge of otoliths (Li, Na, Mg, Mn, Co, Sr, Ba). Of these, Na, Mg, Co and Ba differed among treatments, being highest in treatments where the otolith remained in the head. Variation in element measurements due to treatment effects was similar to within-otolith variation for the other elements and was least variable in the fresh treatment. The variation in concentration between the core and edge was more significant than other sources of variation (up to 100 times) for some elements. These differences were probably due to physiological factors (ontogenetic) or to yearly changes in water chemistry. The results indicate that the method of otolith storage, especially freezing whole fish, can have a small, but measurable, effect on the concentrations of Na, Mg, Co and Ba.     

江苏海岸带陆生盐土植物矿质元素含量的特点及生物循环

陆生盐土植物在生长过程中吸收积累了大量的Cl和Na;从海向陆随着土壤和植被的生态演替,植物中Cl和Na的浓度逐渐降低;N与Cl、Na有相似的水平分布规律;植物种类是影响元素吸收积累的主要因素。在盐地碱蓬中N、P、K、Ca、Mg、Na、Cl、Mn和Zn的含量均是生长前期较高,随着其生长老化逐渐降低,大穗结缕草、白茅与盐地碱蓬相比,Ca的含量前期低后期高,Na、Mn、Cu和Zn的季节变化不明显。参加盐地碱蓬系统生物循环的元素中,Cl和Na的比例最大,在大穗结缕草和白茅生态系统中比例较小;由于白茅被收割利用,一些元素从此生态系统中流失。     

Otolith microstructure and daily age of Anguilla japonica, Temminck & Schlegel elvers from the estuaries of Taiwan with reference to unit stock and larval migration

To test the hypothesis that the Japanese eel, Anguillu japonica , elvers in the eastern and western coasts of Taiwan are recruited from two different spawning grounds and to increase the knowledge of the early life history of the eel, the otolith microstructure and daily age of elvers collected from five estuaries in the coast of Taiwan during December 1989 through February 1990 were examined by scanning electron microscopy. The total length of elvers at arrival in the estuaries was similar among estuaries, averaging c . 56.0 mm and showed a seasonal decrease. The maximum radius of the sagittal otolith of elvers ranged from 124.46 to 181.82μm with a mean of 143.15 ± 12.72 μm. The otolith from centre to edge included an organic-rich primordium (9.20 ± 2.02 μm in diameter), a diffusively calcified core (20.94 ± 1.99 μm), and the daily growth increments; these three layers were probably deposited during the embryonic, yolk sac and feeding period respectively. The growth rate of the otolith was higher at the beginning of early life (0.5−1.0 μm day ⁻¹), lowest at approximately 100-days old (<0.5 μm day⁻¹), and highest 1 month before arrival at the estuary (> 1.0 pm day⁻¹). The mean age for elvers arriving in the estuaries of the coasts of Taiwan was approximately 170.4 ± 21.02 days. Neither the growth pattern of the otolith nor the age of elvers arriving in the estuary were significantly different among estuaries, indicating that the elvers in both eastern and western Taiwan were probably recruited from the same spawning ground. The growth pattern of the otolith in relation to larval migration was analysed.     

Elemental signature in otolith nuclei for stock discrimination of anadromous tapertail anchovy (Coilia nasus) using laser ablation ICPMS

The elemental signature in otolith nuclei was determined using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) for stock discrimination of adult anadromous tapertail anchovy, Coilia nasus, in five Chinese estuaries. Five elements (Na, Mg, K, Sr, and Ba) were well detected in the otolith nuclei of the adult fish. Results showed that the elemental composition in the otolith nuclei varied substantially among the estuaries. Age and fish length data showed no significant influences on the elemental concentration ratios across the sample sites. The Sr:Ca and Ba:Ca ratios were inter-site distinct and could be used as natal tags for discriminating among stocks. Discriminant function analyses (DFA) showed that these ratios can be used in discriminating the Liaohe River estuary (LD, 92.3?%), the Yangtze River estuary (CJ, 86.7?%), and the Yellow River estuary (HH, 76.9?%) samples with high classification accuracy, followed by the Haihe River estuary (BH, 58.3?%) and the Daguhe River estuary (JZ, 46.2?%) samples. An overall classification accuracy rate of 72.7?% from the discriminant functions indicated that elemental fingerprinting appeared to have the potential to discriminate between tapertail anchovy stocks in these estuaries.     

Environmental signature in the otolith elemental fingerprint of the tapertail anchovy, Coilia mystus, from the Changjiang estuary, China

The ontogenetic patterns of habitat use and the migratory history of the tapertail anchovy, Coilia mystus, collected in the Changjiang estuary around Chongming Island, China, were studied by examining the environmental signature in the otolith strontium (Sr) and calcium (Ca) fingerprints using electron probe microanalysis (EPMA). Our results suggest that the migration strategy of C. mystus is much more flexible than supposed in the literature to date. The spring spawning population of C. mystus from the studied area was found to consist of individuals with different migration histories. Although the tapertail anchovy seems to be an anadromous fish that spawns and hatches in a freshwater habitat, it can also use a freshwater environment in non‐spawning seasons. The otolith EPMA of the elemental fingerprint (Sr x‐ray maps and Sr : Ca ratios) is an environmental indicator that can be applied to the migratory ecology of other important diadromous species in China.     

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

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

A histological study on the development of the digestive system of Pseudosciaena crocea larvae and juveniles

The ontogenetic development of the gut and accessory organs in large yellow croaker Pseudosciaena crocea was investigated using light microscopy from hatching up to the juvenile stage (40 days post hatch, dph). At 3 dph (mean ±  s . d ., 4·1 ± 0·1 mm total length, L _T), coinciding with the buccopharynx opening, larvae started to feed exogenously, and the gut consisted of a well‐developed buccopharynx, a partially‐differentiated oesophagus and an intestine divided in three regions (anterior intestine, intermediate intestine and rectum). Yolk reserves were not completely depleted at the onset of exogenous feeding, and a period of mixed nutrition was observed up to 6 dph (4·3 ± 0·1 mm L _T), when yolk was definitively exhausted. Important morphological changes occurred at the end of the larval period, coinciding with metamorphosis. At 17 dph (6·8 ± 0·6 mm L _T), pyloric caeca differentiated at the junction of the pyloric stomach and the anterior intestine. Gastric glands were first observed at 21 dph (9·2 ± 1·2 mm L _T), coinciding with the morphological development of the stomach in three different regions (cardiac, fundic and pyloric) according to the histological characteristics of their mucosa. At this age, large longitudinal folds appeared in the median and posterior oesophageal mucosa. These morphological and histological features suggested the achievement of a digestive system characteristic of large yellow croaker juveniles and adults.     

Competitive inhibition and selectivity enhancement by Ca in the uptake of inorganic elements (Be, Na, Mg, K, Ca, Sc, Mn, Co, Zn, Se, Rb, Sr, Y, Zr, Ce, Pm, Gd, Hf) by carrot (Daucus carota cv. U.S. harumakigosun)

We investigated the uptake of inorganic elements (Be, Na, Mg, K, Ca, Sc, Mn, Co, Zn, Se, Rb, Sr, Y, Zr, Ce, Pm, Gd, and Hf) and the effect of Ca on their uptake in carrots (Daucus carota cv. U.S. harumakigosun) by the radioactive multitracer technique. The experimental results suggested that Na, Mg, K, and Rb competed for the functional groups outside the cells in roots with Ca but not for the transporter-binding sites on the plasma membrrane of the root cortex cells. In contrast, Y, Ce, Pm, and Gd competed with Ca for the transporters on the plasma membrane. The selectivity, which was defined as the value obtained by dividing the concentration ratio of an elemental pair, K/Na, Rb/Na, Be/Sr, and Mg/Sr, in the presence of 0.2 and 2 ppm Ca by that of the corresponding elemental pair in the absence of Ca in the solution was estimated. The selectivity of K and Rb in roots was increased in the presence of Ca. The selectivity of Be in roots was not affected, whereas the selectivity of Mg was increased by Ca. These observations suggest that the presence of Ca in the uptake solution enhances the selectivity in the uptake of metabolically important elements against unwanted elements.     

Migratory patterns and contribution of stocking to the population of European eel in Lithuanian waters as indicated by otolith Sr:Ca ratios

Otolith Sr:Ca ratios were examined to evaluate the contribution of the stocked eel Anguilla anguilla elvers, which have been stocked in Lithuanian waters and mixed with naturally recruited eels for several decades, to the native eel population. Stocked eels were identified by the freshwater signature (Sr:Ca ratios <2·24 × 10⁻³) on the otolith after the glass eel stage. Naturally recruited eels, that had migrated through the North and Baltic Seas, were characterized by an extended seawater and brackish-water signature (Sr:Ca ratios >3·23 × 10⁻³) after the glass eel stage. Of 108 eels analysed, 21 eels had otolith Sr:Ca ratio profiles consistent with stocking while 87 showed patterns of natural recruitment. The ages of naturally recruited eels arriving in Lithuanian fresh waters varied from 1 to 10 years, with a mean ±  s.d . age of 5·2 ± 2·1 years. Eels from the inland Lake Baluošai were all freshwater residents of stocked origin. Stocked eels, however, accounted for only 20% of the eels from the Curonian Lagoon and 2% of eels sampled in Baltic coastal waters. This finding does not support the hypothesis that the eel fishery in the Curonian Lagoon depends mostly on stocking.     

The effects of temperature and water concentration on the otolith incorporation of barium and manganese in black rockfish Sebastes melanops

Observations of multiple years of geographic variation in [Ba:Ca]_otolith and [Mn:Ca]_otolith in black rockfish Sebastes melanops prompted this study to examine the effects of temperature and water concentration on the otolith incorporation of Ba and Mn in this wholly marine species. The replicated experiment design consisted of two water temperatures (7·4 and 13·0° C) and four water concentrations of Ba:Ca and Mn:Ca. A positive, linear relationship between [Ba:Ca]_water and [Ba:Ca]_otolith was observed at both temperatures. A positive temperature effect was also observed with mean partition coefficients for Ba ( D _Ba) greater in the 13° C than in the 7·4° C treatments (mean = 0·061 and 0·048, respectively). There was no relationship between [Mn:Ca]_water and [Mn:Ca]_otolith although a negative temperature effect was observed. Mean partition coefficients for Mn ( D _Mn) were lower in the 13° C than in the 7·4° C treatments (mean = 0·027 and 0·036, respectively). The data presented support the assumption of a positive, linear relationship between water and otolith Metal:Ca concentrations for Ba:Ca but not for Mn:Ca. Thus, although indicative of residence in distinct water masses, observed variation in [Metal:Ca]_otolith may not reflect variation in water concentration and can be affected by temperature. Caution should be applied in the interpretation of geographic variation of [Mn:Ca]_otolith until the mechanisms regulating its incorporation are more fully understood.     

Reproduction and larval biology in tunas,and the importance of restricted area spawning grounds

Tunas show a wide variety of life history strategies, spatial distributions and migratory behaviors, yet they share a common trait of spawning only in tropical and sub-tropical regions. The warm-water tuna species generally show significant overlap between spawning and feeding grounds, and longer spawning seasons of several months to near year-round. In contrast, the cool-water bluefin tunas migrate long distances between feeding and spawning grounds, and may spawn over periods as short as 2 months. Here, we examine the spatial distributions of tuna larvae in the world’s oceans, and examine interspecific differences in the light of adult behaviors and larval ecology. We discuss the links between larval tuna and their oceanographic environments and relate these to current knowledge of larval growth, feeding and trophodynamics, with a focus on the better-studied bluefin tunas. We show that larval tunas have moderate to fast growth rates and selective feeding habits, and thus appear to be adapted for survival in warm, oligotrophic seas. We also examine the challenges of sustainably managing species which migrate across multiple management boundaries to reach spatio-temporally restricted spawning grounds and discuss the previous and future anthropogenic impacts on tuna spawning areas.