Validation of first annulus formation in red snapper otoliths with the use of an alizarin complexone fluorescent marker

The red snapper (Lutjanus campechanus) is among the most studied reef fish species in the Gulf of Mexico. Several studies have used counts of annuli in sectioned sagittal otoliths to age red snapper. However, interpretation of the putative first annulus has been a major source of debate among otolith readers throughout the Gulf of Mexico. Our objective was to use the chemical marker alizarin complexone to validate the periodicity of first opaque annulus formation in red snapper otolith sections. Juvenile red snapper were immersed in 100 mg alizarin complexone per L seawater solution in November 2005 and then reared in 6000 l circular tanks until July 2006. Otoliths were then removed from the fish and thin sectioned. All experimental otolith sections displayed a distinct fluorescent mark ranging from 0.62 to 0.96 mm from the core when viewed under the microscope with a rhodamine filter. The diffuse opaque annulus was located distally to the alizarin mark in all specimens (ranging from 0.88 to 1.51 mm). The distal position of the presumptive first annulus relative to the alizarin mark in all specimens indicates that this diffuse opaque annulus in red snapper sectioned otoliths forms during the first winter after hatching. Translucent marginal edges of all otolith sections indicate that first opaque annulus formation is completed by mid-July.     

Validation of annulus formation in otoliths of largemouth bass Micropterus salmoides outside their native range

The periodicity of growth zone formation was validated for largemouth bass Micropterus salmoides using edge analysis (EA) and mark recapture of chemically‐tagged wild fish (MRCT) to test the hypothesis that one opaque and hyaline zone was deposited annually in sagittal otoliths sampled from temperate South African M. salmoides populations. For 35 fish recaptured in the MRCT experiment, the relationship between the number of growth zones posterior to the chemical mark and the time at liberty (0.04–1.38 years) did not differ significantly from a 1 : 1 relationship (t‐test, t = 0.76, d.f. = 2,33, P = 0.45). This result was supported by EA, where periodic logistic regression and a binomial model linked with a von Mises distribution for circular data demonstrated that the frequency of otoliths with opaque margins followed a unimodal distribution (maximum October–January). Both the timing of growth zone deposition (spring) and the annual rate were consistent with results from validation studies conducted globally in localities ranging from 45°N to 33°S, and indicate that the growth zone deposition rate is annual throughout the native and introduced range of this species.     

Morphology and microchemistry of abnormal otoliths in the ayu, <Emphasis Type="Italic">Plecoglossus altivelis</Emphasis>

The sagittal otolith morphology and microchemistry of reared juvenile ayu, Plecoglossus altivelis, were examined to describe the occurrence and microchemical characteristics of the abnormal otoliths in this species. Juvenile ayu (N = 31) were collected in June 2004 at three different locations, Wakayama, Kumamoto, and Biwa Lake in Japan, where they were being reared in freshwater aquaculture ponds after having been collected in the wild as larvae. Otolith abnormality was found in the sagittae of 26% (N = 8) of the individuals examined, of which five fish had abnormal otoliths only on one side, while the otolith on the other side was normal. Abnormal otoliths were more transparent and crystalline in appearance with irregular shapes compared to normal ones that were more opaque and less irregular. Abnormal otoliths were divided into two types, semi-abnormal (Type 1) with a normal part in the center, and fully-abnormal (Type 2) that were completely crystalline in appearance. The line transects and whole otolith concentration maps showed that the contents of Sr, Na and K were lower in the abnormal otolith regions compared to the normal ones, while those of Ca and S were almost constant in both. The appearance and microchemical properties of the abnormal ayu otoliths were similar to the abnormal otoliths in other species in which vaterite replaces the aragonite. Abnormal formation of otoliths occurred in ayu from Biwa Lake (30%) and Kumamoto (45%), while the Wakayama samples had no abnormality. The microchemical analyses of the normal and abnormal otoliths indicated that some abnormal otoliths had formed before the fish were captured and transferred to the hatchery, so the possible causes of otolith abnormality in ayu are discussed.     

Effect of predator exposure on the performance and survival of red drum (<Emphasis Type="Italic">Sciaenops ocellatus</Emphasis>)

The influence of predator exposure on the survival of hatchery red drum, Sciaenops ocellatus was investigated under laboratory conditions. Several prey-capture (attack distance, mean attack velocity, capture time, and gape cycle duration) and anti-predator (reaction distance, response distance, mean velocity, and maximum velocity) performance variables were quantified using high-speed video for juvenile red drum (25–30 mm standard length, L _S ) reared with and without predators (pinfish, Lagodon rhomboides). Univariate contrasts of prey-capture events demonstrated that attack distance (mean ± s.e.) was significantly greater in red drum reared with (1.20 ± 0.16 mm) versus without (0.65 ± 0.09 mm) pinfish predators. During anti-predator events, red drum reared with predators had approximately 300% greater reaction distance and 20%–30% greater response distance, mean velocity and maximum velocity versus fish reared without predators; however, these differences were not statistically significant. Following video assessments, a series of mortality experiments were conducted using free-ranging pinfish predators. Mortality rates (Z) ranged from 0.047 to 0.060 (Z/hr/predator) and did not differ significantly among treatments.     

Age estimation and validation for South Pacific albacore Thunnus alalunga

Validated estimates of age are presented for albacore Thunnus alalunga, sampled from a large part of the south‐western Pacific Ocean, based on counts of annual opaque growth zones from transverse sections of otoliths. Counts of daily increments were used to estimate the location of the first opaque growth zone, which was completed before the first assumed birthday. The periodicity of opaque zones was estimated by marginal increment analysis and an oxytetracycline mark–recapture experiment. Both validation methods indicated that opaque zones formed over the austral summer and were completed by autumn to winter (April to August). The direct comparison of age estimates obtained from otoliths and dorsal‐fin spines of the same fish indicated bias, which was assumed to be due to poor increment clarity and resorption of early growth zones in spines, resulting in imprecise age estimates. As such, age estimates from otoliths are considered to be more accurate than those from spines for T. alalunga. This is consistent with results for a growing number of tropical and temperate tuna Thunnini species. It is recommend that validated counts of annual growth zones from sectioned otoliths is used as the preferred method for estimating age‐based parameters for assessment and management advice for these important stocks.     

Using otoliths to estimate age and growth of a large Australian endemic monocanthid, <Emphasis Type="Italic">Nelusetta ayraudi</Emphasis> (Quoy and Gaimard, 1824)

Nelusetta ayraudi (the ocean leatherjacket) is an endemic Australian monacanthid species distributed from North West Cape (Western Australia) south to southern Queensland. The commercial and recreational fisheries targeting Nelusetta ayraudi have expanded substantially along the coast of New South Wales (NSW) in recent years but there exists little biological information on which to base effective management of this growing fishery. World-wide, only a few studies have aged monacanthids. Of these, researchers have interpreted periodic increments in bony structures such as vertebrae and anterior dorsal spines in preference to those found in otoliths. In this study we estimated age of N. ayraudi by counting growth increments in sectioned otoliths. The periodicity of increment formation was validated using a vital stain, (oxy-tetracycline), injected into young-of-the-year fish. Growth was rapid especially as juveniles with N. ayraudi attaining approximately 220 mm after 1 year and 340 mm after 2 years. No differences in growth rates were detected between sexes or between fish captured at different latitudes (zones). The largest male (605 mm, Total Length—TL) and female (656 mm, TL) were both recorded from northern NSW, with both sexes attaining the maximum age of 6+ years from northern and southern NSW. The von Bertalanffy parameters describing growth for N. ayraudi were L_￥ {L_\infty }  = 591 mm (TL), k = 0.377 year⁻¹ and t _o = −0.247 years.     

Use of otoliths to determine age and growth of a tropical flatfish Cyclopsetta querna (Paralichthyidae) from the southeast coast of the Gulf of California, Mexico

Age and growth of the tropical flatfish Cyclopsetta querna were determined from the sagittal otoliths. From yearly marginal growth increment trends, it was concluded that the opaque and hyaline zones were formed annually. The oldest individual was a 43.2-cm (5-year-old) female. No significant differences in length-at-age were found between sexes. The von Bertalanffy growth equation for the entire population was L_t = 60.71 (1 − e ^{(−0.245(t−0.408))}). The life span of these species is short, about 5 years. The otoliths proved a reliable structure to determine age of this species.     

Validation of daily increment formation in otoliths for Gymnocypris selincuoensis in the Tibetan Plateau,China

Daily increment validation in fish otolith is fundamental to studies on fish otolith microstructure, age determination and life history traits, and thus is critical for species conservation and fishery management. However, it has never been done for Schizothoracine fish, which is the dominant component of fish fauna in the Tibetan Plateau. This study validated the daily increment formation of Gymnocypris selincuoensis, as a representative of Schizothoracine fish, by monitoring the growth of hatchery‐reared larvae group and wild‐caught post‐yolk‐sac larvae group under controlled experiments. The results from monitoring the hatchery‐reared larvae group showed that sagittae and lapilli were found in yolk‐sac larvae, and formed 5–7 days before hatching, but asterisci were not found until 11 days post‐hatching. The first increment in sagittae and lapilli was formed in the first day after hatching. The daily periodicity of increment formation was examined and confirmed in sagittae and lapilli of both larvae groups. However, sagittae were better for age determination than lapilli for larvae at earlier days. For larval G. selincuoensis older than 50 days, lapilli were the only otolith pair suitable for larvae daily age determination. This study validated the daily increment formation in Schizothoracine fish for the first time has primary implications to other fishes from this subfamily.     

Verification of daily growth increment formation in saury otoliths by rearing larvae from hatching

Naturally spawned eggs of the Pacific saury,Cololabis saira, were collected in the field and reared in a tank to examine daily periodicity of growth increment formation in the otolith. Larvae were 6.9 mm in knob length at hatching. Their otoliths (sagittae) were 31 μm in radius and had 3–6 faint concentric rings. They started feeding within two days and grew at a rate of 1.1 mm/day on average through larval and juvenile stages feeding on rotifers,Artemia nauplii, and artificial diets. Otolith growth increments showed a concentric pattern with a distance of 3.5–5.0 μm between two adjacent increments. The number of growth increments was almost equal to a known age in days plus 4 or 5. A regression line of number of increments (N) on known age in days (D) between 0–30 days after hatching was N = 4.81 + 1.01D, which shows that one increment was deposited per day.     

Preliminary estimates of the age and growth of immature smooth oreo Pseudocyttus maculatus Gilchrist 1906 (Oreosomatidae) in the Falkland Islands region of the South Atlantic

Sectioned otoliths were used to estimate the age of 29 specimens of the smooth oreo (Pseudocyttus maculatus Gilchrist 1906) from the Falkland Islands region of the South Atlantic. This represents the first ageing study of this species in this region of the world. All specimens were immature (sub-adults), the largest having a maximum total length of 347 mm. Growth increments were observed in sectioned otoliths and assumed to be annual in periodicity. The maximum age estimate of individuals in this study was 20 years and the form of somatic growth was similar to previous research on this species from Australian waters. The otolith microstructure consisted of an inner, mostly opaque zone with wide increments followed by an outer, mostly translucent zone with narrower increments. It is suggested that these zones correspond to the two growth phases in the life history of this species, namely the pelagic juvenile phase (opaque zone) and the demersal sub-adult/adult phase (translucent zone). Received: 27 May 1997 / Accepted: 31 October 1997     

The use of otolith shape analysis for ageing juvenile red snapper, Lutjanus campechanus

Morphological changes in otolith shape with age, of young (<age 3) red snapper were examined through shape analysis and tested as an objective method for age determination. Otoliths from two collections of juvenile fish (hatchery and wild) were used in the study. First, shape analysis was applied to a series of known-age otoliths from hatchery-reared age 0, 1 and 2 fish. Multidimensional scaling and non-parametric analysis of similarities showed significant shape differences among the three age classes of fish. Discriminant function analysis and cross-validation classification showed 65.6% correct age classification based on shape variables alone, and 86.7% correct age classification with inclusion of otolith weight in the discriminant function (n?=?90). Subsequently, the method was applied to otoliths from a series of age 0, 1 and 2 wild caught red snapper. Otoliths from wild fish showed a similar age classification success rate of 68.9% based on shape variables alone and 86.7% correct age classification with the inclusion of otolith weight in the discriminant function (n?=?90). Ageing of juvenile red snapper through otolith increment counts has been difficult in past studies and this study provides an alternative, objective method of otolith shape analysis for ageing young fish of this species.     

The effect of feeding rate on growth of pectoral fin spine of juvenile great sturgeon Huso huso (Linnaeus, 1758)

The effect of two feeding rates (0.5 and 1.5% of total body weight) was assessed on the growth of pectoral fin spines of captive juvenile great sturgeon, Huso huso, after second year of life. The fish received Oxytetracycline (OTC) twice in the first and second years of their lives under basic diet. During the 5‐month experimental period, juveniles (mean 1,187.4 g, 0.1 standard deviation [SD]), n = 50) were reared with two feeding rates under similar conditions in 10 fiberglass tanks (1.5 m³). The fish were fed manually with a commercial diet twice a day (35% Biomar, Nersac, France) throughout the experiment. The OTC marks were distinguished in all pectoral fin spine sections under ultraviolet light. The means of the first and second annular radii were 806.6 µm (27.2 SD) and 2,246.5 µm (50.2 SD), respectively. The marginal increment analysis beyond the second OTC mark revealed a significantly smaller marginal increment for low feeding rate treatment (143.9, 11.2 SD) as compared to the high feeding rate one (269.0, 14.6 SD). The results indicate the slower growth rate in the fish fed the low feeding treatments seen in the pectoral fin spine formation, which can be used as an indicator of recent feeding history in sturgeon juveniles. The best daily feeding rate for great sturgeon of 2,460 g was determined to be 1.5% body weight/day in this study.     

Age and growth of <Emphasis Type="Italic">Schizothorax waltoni</Emphasis> in the Yarlung Tsangpo River in Tibet,China

Age and growth were studied for Schizothorax waltoni in the middle reaches of the Yarlung Tsangpo River in Tibet, southwest of China, from April 2004 to September 2006. A total of 201 specimens were collected ranging from 110 to 580 mm in standard length (SL). In contrast to other otoliths, sectioned lapillus showed a clear pattern of alternating opaque and hyaline zones. Marginal increment analyses showed that the increments, each composed of one opaque and one hyaline zone, are deposited annually. Opaque edges were prevalent from May to August. The von Bertalanffy growth parameters based on sectioned otolith data were L _t  = 689.8{1 − exp[0.051 (t + 3.275)]} for males, and L _t  = 691.1{1 − exp[0.056 (t + 2.466)]} for females. The slow growth and long life indicate that S. waltoni is vulnerable to overfishing and that harvesting strategies for the species should be conservative.     

Age and growth of a sub-Antarctic notothenioid, Patagonotothen ramsayi (Regan 1913), from the Falkland Islands

The Falklands’ rockcod Patagonotothen ramsayi was aged successfully using whole and sectioned otoliths. Marginal increment analysis showed that one opaque and one translucent zone were laid down each year. Counting daily rings in juvenile fish and back calculating to their assumed hatch dates validated the first annulus. Readings taken from scales and otoliths showed good agreement with no significant difference between them (P>0.05). Inter- and intra-reader comparisons also showed good agreement. The maximum estimated age was found to be 14 years and the calculated von Bertalanffy growth curve L _T =33.77(1−e ^{−0.25year(t+1.07)}) showed that P. ramsayi is a relatively slow growing fish that attains 5–6 cm L _T in its first year and after which grows approximately 3 cm per year until 4 years. Males seemed to have a slightly lower growth rate but attained a greater maximum size than females. The formation of annuli in the otoliths of P. ramsayi seems to coincide with periods of high reproductive activity with both peaks in GSI and the prevalence of translucent margins occurring in July.     

Pelagic larval duration and population connectivity in New Zealand triplefin fishes (Tripterygiidae)

The relationship between pelagic larval duration (PLD) and population connectivity in marine fishes has been controversial, but most studies to date have focused on tropical taxa. Here, we examine PLD in 11 species of triplefin fishes from a temperate environment in the Hauraki Gulf, New Zealand, to describe daily increment patterns and settlement marks in the otoliths. The formation of daily increments was validated using larvae of known age and tetracycline marking of settled juveniles. Settlement mark identity was verified by comparing total increment counts from otoliths of recently settled fishes with PLD counts from post-settlement fishes. A similar pattern of three groups of increments across the otolith was found in all specimens examined. The settlement mark was similar in all species and occurred as a sharp drop in increment width within the area of transition in optical density. PLD was lengthy, compared to species of triplefins from elsewhere, and ranged between 54.4 ± 1.7 SE days in Bellapiscis lesleyae to 86.4 ± 2.6 SE days in Forsterygion malcolmi. Variation in PLD within species was high but did not mask interspecific differences. PLD was not phylogenetically constrained, as sister species differed significantly in PLD. PLD was compared with genetic population connectivity for eight of the study species using mitochondrial gene flow data from Hickey, Lavery, Hannan, Baker, Clements. Mol Ecol 18:680–696 (2009). The observed lack of correlation between PLD and gene flow suggests that dispersal is limited by other factors, such as larval behaviour and the availability of settlement habitat.     

Comparison of growth rate and formation of otolith increments in age-0 red snapper

For wild red snapper Lutjanus campechanus , mean otolith increment deposition rate after marking with oxytetracycline dihydrate (OTC) was daily (0.97 increments day⁻¹) when growth rates were fast (0.63 mm fork length, L _F day⁻¹), but were not daily (0.82 increments day⁻¹) when somatic growth was slow (0.2 mm L _F day⁻¹). For reared larvae ( n =8), increment deposition rates were daily (0.99–1.03 increments day⁻¹), and growth rates ranged from 0.6 to 0.9 mm L _F day⁻¹. Growth rate affected increment deposition rate as a threshold function, i.e. when growth rate was <0.3 mm L _F day⁻¹, deposition was less than daily, but above this level increment deposition did not exceed a daily rate. As growth rates increased increment widths increased. Examination of a sub-sample ( n =8) of the otoliths from the slowest growing wild fish by scanning electron microscopy did not increase increment counts. Because L. campechanus are late spring-early summer spawners, young fish can expect maximum growth due to warm summer temperatures. Thus, daily ageing methods should be well suited to this species.     

Age validation,and comparison of otolith,vertebra and opercular bone for estimating age of <Emphasis Type="BoldItalic">Schizothorax o’connori</Emphasis> in the Yarlung Tsangpo River,Tibet

A collection of 514 Schizothorax o’connori was made between August 2008 and August 2009 from Yarlung Tsangpo River to assess the suitability of three bony structures for age estimation. The annulus characteristics of otolith, vertebra and opercular bone were described. Location of the first annulus was validated by daily growth increment (DGI) analysis in the otoliths. Annual periodicity was verified by marginal increment ratio (MIR) analysis in otoliths and edge analysis in vertebrae and opercular bones. Annuli formed, once a year, between March and May for all three bony structures. Otoliths, vertebrae and opercular bones were examined to determine which structure produced the most precise and accurate age estimates in S. o’connori. Vertebrae and otoliths matched closely for the first 21 years of life, while opercular bones appeared to underestimate age. For older fish, the counts diverged and otoliths consistently providing higher age estimates. Sectioned otoliths proved to be the most precise and accurate structure for age estimation. The oldest observed schizothoracine fish was 50, more than twice the longevity previously accepted in S. o’connori.     

Validation of annulus in otolith and estimation of growth rate for Japanese eel <Emphasis Type="Italic">Anguilla japonica</Emphasis> in tropical southern Taiwan

The age of Japanese eels (Anguilla japonica) is often estimated from otoliths, but this method has not been fully validated, particularly in tropical areas where the annulus in otolith is considered to be less distinct than in temperate areas. To validate the annuli in Japanese eel otoliths from southern Taiwan, known-age (2 year-old) cultured eels from an eel farm and wild eels from Kao-Ping River were collected. It was found that 26 out of 31 cultured eels (83.9%) showed two clear annuli and the remained 5 eels showed either one or three annuli. The mean (± SD) age of the cultured eels was 1.97 ± 0.4 years. Meanwhile, a clear peak in the mean monthly marginal increment ratio of the otolith in wild yellow and silver eels occurred once a year during winter (November to March). The annual deposition of presumed annuli in otoliths of Japanese eel was validated and the age and growth rate estimation for Japanese eels in the tropical southern Taiwan is deemed feasible. The growth rate of cultured eels was significantly faster than that of wild eels, but it did not differ significantly between sexes for wild silver, yellow or cultured eels. The von Bertalanffy Growth Function parameters (K, and t ₀ ) of the wild eels were estimated as 0.114 ± 0.028 year⁻¹, 1178 ± 171 mm and −0.8 ± 0.2 years, respectively.     

Using cross-dating techniques to validate ages of aurora rockfish (<Emphasis Type="Italic">Sebastes aurora</Emphasis>): estimates of age,growth and female maturity

Since fishery management regulations have shifted much of the groundfish trawl effort in the northeastern Pacific from the continental shelf to the slope, fishery impacts on unassessed demersal slope rockfish species like the aurora rockfish (Sebastes aurora) may have increased. Understanding the life history of these species is a critical first step in developing management strategies to protect them from overharvest. In this study we employ cross-dating methods to validate the annual periodicity of growth increments and investigate the age, growth and maturity of aurora rockfish, a species for which life history information is quite limited. Specimens were collected on an opportunistic basis from Oregon commercial landings and from research cruises, over the years 2003–2006. Age was estimated for 438 individuals using otoliths processed via the break-and-burn method. The maximum estimated age was 118 years for females (n = 324) and 81 years for males (n = 114). The von Bertalanffy growth function showed that males grow faster and reach a smaller maximum size than females (males: L _inf = 34, K = 0.09, t ₀ = −1.9; females: L _inf = 37, K = 0.06, t ₀ = −5.5), though both sexes demonstrate relatively slow growth. Visual assessment of ovaries showed that the aurora rockfish is a synchronous spawner with parturition occurring in May and June off Oregon. Female age and length at 50% maturity were calculated at 12.6 years and 26 cm, respectively (n = 307). Maturity and age data provided evidence for a protracted adolescence in this species.     

Ring formation on otoliths and scales of Pagrus pagrus: a comparative study

One annulus formed on the scales of farmed red porgy Pagrus pagrus each year during March and one opaque zone on the otoliths during June. Scales proved to be more sensitive than otoliths in recording the life history of the red porgy. A false annulus (ring of capture) was observed on the scales of the 0+ age group, but not on the otoliths. A gradual lengthening of the period of annulus formation was observed, from the younger to the older fish. The annulus formation in fish older than 2+ was less synchronized, due to the aquaculture conditions. Scales were more accurate than otoliths in annuli formation. A high percentage of missing or additional opaque zones were observed on otoliths of older fish. These irregularities were related to fish maturation and/or farming conditions. Farmed fish grew three times as fast as the wild fish.