Opaque Zone Formation Research Articles

Validation of Annuli and Identification of Discontinuities in Sagittal Otoliths of Juvenile Alligator Gar

AbstractAnnual increment periodicity has been validated in sagittal otoliths of Alligator Gar Atractosteus spatula; however, discontinuities (often referred to as false annuli or checks) are common in early years, potentially affecting both accuracy and precision. We used up to four injections of oxytetracycline (OTC) to induce time stamps associated with annuli (opaque zones) in the otoliths of juvenile Alligator Gar (ages 2–6; n = 68). These OTC marks allowed us to test a reader's ability to distinguish discontinuities (hereafter, “checks”) from annuli by using established criteria. In addition, the OTC marks were used to infer the timing of translucent zone and opaque zone formation. Although the reader's error rate was low (6%), some checks were essentially indistinguishable from annuli. Checks were common, occurring in over half of the otoliths examined and within all annual increments in these juvenile fish. The association of all OTC marks with the opaque zones of the annual increment further validates annulus formation in juvenile Alligator Gar and indicates that these narrow zones formed approximately between November and June. Subsequently, it can be inferred that the much wider translucent zones formed from about June to November. Although opaque zone formation was complete by June, new annuli were not distinguishable from the ventral edge of the otolith until translucent material was deposited beyond the annuli. In our samples, only 22.2% of the otoliths from fish sacrificed on June 30 (n = 9) had fully visible annuli along the edge of the otolith. Based on multiple studies, it is apparent that annual increments form in the sagittal otoliths of Alligator Gar throughout their lives; however, the interpretation of these increments can be very difficult. In our experience, the OTC marking of fish can provide a valuable tool for training and verification programs needed for this species and for other long‐lived fishes that pose difficulties in age estimation.

Age, Growth, and Mortality Rates of the Giant Cichlid in Guatemala

AbstractAge, growth, and mortality were assessed in Giant Cichlids Petenia splendida from lakes in northern Guatemala by using cross‐sectioned sagittal otoliths. Marginal increment and edge analyses of Giant Cichlid otoliths indicated that one annulus formed per 12‐month period in Lakes Yaxhá and Petén Itza. Opaque zone formation was associated with the peak of the rainy season from May to September. Ages ranged from 0 to 8 years for Giant Cichlids in Lake Yaxhá and from 0 to 5 years in Lake Petén Itza. Within both lakes, males were larger than females, although the difference was slight in Lake Petén Itza. Lake Yaxhá Giant Cichlids had faster growth rates than those from Lake Petén Itza, and fish over 2 years old from Lake Yaxhá were larger at age than fish from Lake Petén Itza. This is counter‐intuitive because Lake Petén Itza is heavily exploited, whereas Lake Yaxhá is unfished. However, long‐term exploitation in Lake Petén Itza may have resulted in selection for fish with reduced growth rates. Alternatively, the mesotrophic state of Lake Yaxhá may explain the differences in growth, although areas of Lake Petén Itza are changing from oligotrophic to meso‐eutrophic due to rapid cultural eutrophication. Total mortality (Z) estimates for Giant Cichlids were 0.81 for Lake Yaxhá, with most of the age structured on 2–4‐year‐old fish, and 1.05 for Lake Petén Itzá, where the age structure was dominated by 0–2‐year‐old fish; these results were consistent with expectations based on the low fishing pressure in Lake Yaxhá.

Life-history characteristics of Pseudoplatystoma metaense (Teleostei: Siluriformes: Pimelodidae) from the northwestern Orinoco River Basin

ABSTRACT The tiger shovelnose catfish (Pseudoplatystoma metaense) identified in literature prior to 2007 as P. tigrinum is the most important catfish species in the Orinoco River fishery, because of its abundance and high market price. The aim of this study was to obtain age, growth and population parameters of the of tiger shovelnose catfish. A total of 2,183 catfish, were sampled during 1996-2003 from the commercial fishery of the northwestern Orinoco River Basin in Venezuela, and were aged by examination of otoliths. Validation of otolith annuli was achieved with marginal increment analysis. Results suggest that, the opaque and translucent zones of otoliths were formed once per year. Length-weight relation and the von Bertalanffy growth model parameters were used to evaluate growth and other population parameters. A strong link between the annual flood pulse and opaque zone formation was confirmed in tiger shovelnose catfish. The total mortality (Z) and natural mortality (M) were estimated. Based in the reference points for optimal and limit fishing mortality rates (F opt and F limit ) this species is exploited above optimum levels. We thus recommend a closed fishing season during their seasonal reproduction, and establishment of a system of fish refuges to help sustain the population.

Timing of growth zone formations in otoliths of the snapper, Chrysophrys auratus, in subtropical and temperate waters differ and growth follows a parabolic relationship with latitude

Chrysophrys auratus was collected from one sub-tropical and two temperate regions spanning >2400 km along the coast of Western Australia (∼23.5–35.5° S). Marginal increment analysis demonstrated that, while a single opaque zone is formed in the otoliths of C. auratus each year, the period of deposition varies among regions. An opaque zone was formed in May to early September in the sub-tropical upper west coast, and thus when water temperatures were declining to their minima. In contrast, opaque zone formation occurred 3 months later in August to December in the temperate lower west and south coasts, when water temperatures were rising from their minima. The length and age distributions differed markedly among populations of C. auratus, with the strongest year classes varying among the three regions. Thus, it is likely that year class strength of C. auratus throughout its distribution along the coast of Western Australian is mostly related to local environmental conditions. Chrysophrys auratus grew far less rapidly and attained a smaller size in the warmer upper west coast than in the cooler temperate regions of the lower west and south coasts. A collation of data on C. auratus from ten populations in Australia and three in New Zealand showed that growth is greatest towards the mid-latitudes of its geographic range, i.e. at ∼31° S. Estimates of mean lengths at specified ages thus exhibit a parabolic relationship with latitude, with reduced growth (i.e. edge-of-range effects) occurring towards the latitudinal margins of the distribution of this sparid.

Age validation, growth and mortality of introduced Tilapia zillii in Crater Lake Nkuruba, Uganda

AbstractPeriodicity and timing of opaque zone formation in otoliths of introduced redbelly tilapia, Tilapia zillii (Gervais), in Crater Lake Nkuruba, Uganda, were validated using marginal increment. Age and growth were assessed through readings of biannuli in thin‐sectioned sagittal otoliths. Deposition of opaque zone formation in T. zillii otoliths was bimodal (March–May and September–November), corresponding to two seasonal peaks of precipitation characteristic of this equatorial region. Ages of T. zillii ranged from 2 to 8 years, with fish gillnetted offshore having a faster growth and attaining larger size‐at‐age than fish captured inshore in minnow traps, suggesting that use of multiple gears is needed when estimating the growth of T. zillii. Total instantaneous mortality (Z), estimated using catch curve analysis, was 0.74 for gillnetted fish and 0.71 for trapped fish. These estimates were at the low end of the total mortality reported for other tilapia species. Natural mortality (M) was estimated as 0.52–0.54 by applying Rikhter and Efanov's maximum age at maturity and Hoenig's maximum age methods, respectively. Fishing mortality (F) in Lake Nkuruba was 0.17–0.22, indicating a low exploitation level in the lake.

Validation of age determination using otoliths of the European anchovy (Engraulis encrasicolus L.) in the Bay of Biscay

Validation of the age determination procedure using otoliths of European anchovy in the Bay of Biscay was achieved by monitoring very strong year-classes in successive spring catches and surveys, as well as the seasonal occurrence of edge types. Historical corroboration of the ageing method was obtained by cross-correlation between successive age groups by year-classes in catches and surveys (1987–2013). Summary annual growth in length is also presented. Yearly annuli consist of a hyaline zone (either single or composite) and a wide opaque zone, disrupted occasionally by some typical checks (mainly at age-0 and age-1 at peak spawning time). Age determination, given a date of capture, requires knowledge of the typical annual growth pattern of otoliths, their seasonal edge formation by ages and the most typical checks. Most opaque growth occurs in summer and is minimal (translucent) in winter. Opaque zone formation begins earlier in younger fish (in spring), and this helps distinguish age-1 from age-2+.

First attempt to age yellowfin tuna, Thunnus albacares, in the Indian Ocean, based on sectioned otoliths

This study first attempts to investigate the age and growth of yellowfin tuna in the Indian Ocean and clarifies its sex-specific growth using sectioned otoliths. The results indicate that the assumption of annual opaque zones may be reliable and fish age at the first opaque zone formation is about 0.75 years. The age estimates cover a large range of lifespans (age estimates range from 0.75 to 10.50 years) in which the maximum age estimate shows that males (9.50 years) are older than females (6.50 years). The estimated von Bertalanffy growth curves are shown to be significantly different between sexes, while the von Bertalanffy growth parameters (L∞, k and t0) are 123.6cm, 0.846 year−1 and −0.449 years for females and 162.9cm, 0.244 year−1 and −2.139 years for males. The growth curves of both sexes are similar before 4 years, after which males start to grow larger than females. Sexual size dimorphism in growth curves occurs after mature age.

On the seasonal pattern of formation of opaque zone on otoliths of the northern rock sole Lepidopsetta polyxystra of the Pacific shelf of Kamchatka and the Northern Kurils

On the seasonal pattern of formation of opaque zone on otoliths of the northern rock sole Lepidopsetta polyxystra of the Pacific shelf of Kamchatka and the Northern Kurils

Age-based demography and relative fisheries productivity of Spanish mackerel, Scomberomorus commerson (Lacepede) in Western Australia

Spanish mackerel, Scomberomorus commerson, is a species of economic and artisanal importance throughout the Indo-West Pacific region. In this study a total of 2973 S. commerson were examined in a comprehensive study of otolith structure and demographic characteristics across multiple management regions along the Western Australian (WA) coast. Marginal increment analysis of sagittal otoliths showed a single annual peak in opaque zone formation indicating that one opaque and translucent band (annuli) is formed each year. Juvenile S. commerson of undifferentiated sex (n=67; 58–709mm FL) ranged in age from 23 days to 350 days. Males (n=1239; 301–1381mm FL) ranged in age from 80 days to 22yrs, and females (n=1273; 396–1720mm FL) ranged in age from 122 days to 18yrs. Significant differential growth was evident between sexes, with females attaining a larger size-at-age than males. Initial growth of S. commerson is rapid with both sexes reaching maturity within 1.5yrs of age. Growth parameters also differed among regions. The instantaneous rate of natural mortality (M) was estimated to be in the range of 0.16–0.20yr−1. The instantaneous rate of total mortality (Z) estimated from catch at age data for fully recruited age classes, was different between sexes and among regions. Significant differences in demography, age structure and otolith readability among management regions support earlier studies that have documented meta-population structure in S. commerson and underpin the regional management regime for this species in Western Australia. Populations of S. commerson have a high production potential given their rapid initial rate of growth and low age at maturity. Despite this high production potential, productivity of this species in WA is relatively low compared to related fisheries throughout the Indo-Pacific region.

Age and growth of the round gobyNeogobius melanostomusin the Gulf of Gdańsk several years after invasion. Is the Baltic Sea a new Promised Land?

The ages of 8 to 23·5 cm total length (L(T)) round goby Neogobius melanostomus collected monthly during 2006 and 2007 in the Gulf of Gdańsk (Baltic Sea) ranged from 2 to 6 years, with age class 4+ years dominant. Males were larger at age than females. The fastest growth occurred in the first 2 years of life in both sexes. Females were heavier at a given L(T) than males, but only for fish > c. 15 cm. A strong relationship between N. melanostomus otolith size and fish size was found, with no difference between males and females, and a significant relationship between fish growth rate and otolith growth rate, which enabled backcalculation of growth rates. Marginal increment width analysis confirmed the periodicity of annual ring formation in otoliths and showed that the most intense opaque zone formation occurs in July to August, while hyaline zone formation starts as early as September to October. It was concluded that the N. melanostomus that have colonized the southern Baltic Sea exhibit the largest size and longest life span ever recorded for this species.

Validation of annual periodicity in otoliths of red snapper, Lutjanus campechanus

The periodicity of otolith growth increments (opaque and translucent zones) from adult red snapper (Lutjanus campechanus) was examined through a mark and recapture study (2005–2010), and laboratory holding of hatchery reared red snapper over a 2 year period (2002–2004). Wild red snapper (n = 295) were caught hook-and-line, marked with anchor tags, injected with oxytetracycline dihydrate (OTC), and released in the Gulf of Mexico 15–40 km south of Dauphin Island, Alabama. Marked fish were recaptured up to 2.8 years after release (n = 35) and sagittal otoliths were dissected, sectioned and examined under white and blue-violet light. The number of opaque growth zones past the OTC mark was compared to time at liberty for each fish and supported an annual periodicity of growth increment formation. Also, most (87%) of the hatchery reared fish showed two opaque zones that supported an annual increment formation rate. However, an unusual timing of opaque zone formation was shown for mark-recaptured fish. Based on known timing of OTC marking, otoliths from mark-recapture fish showed opaque zone formation from late summer (August) to early winter (December). This fall formation of opaque zones is in contrast to previous studies and its timing may relate to the end of spawning for this species.

Changes in the timing of otolith zone formation in North Sea cod from otolith records: an early indicator of climate-induced temperature stress?

We examine the seasonal variation in otolith increment formation in southern North Sea cod as a means of monitoring how changes in sea temperature over the past 20 years have affected cod in the wild. Seasonal opaque zone formation was related to winter and early spring. Timing of opaque zone formation was not influenced by either temperature or fish length, but increasing age led to slightly earlier but slower opaque zone formation. In contrast, there was a clear shift in the timing of translucent zone formation with temperature. In warm years, translucent growth occurs up to 22 days earlier than in colder periods. Increasing age and smaller size-at-age resulted in an earlier transition from opaque to translucent edge formation. Translucent zone formation appears indicative of increasing metabolic stress, and the earlier onset provides direct evidence of the impact of increasing sea temperatures on wild North Sea cod stocks.

Phenology and North Sea cod Gadus morhua L.: has climate change affected otolith annulus formation and growth?

Timing and rate of seasonal zone formation in southern North Sea cod Gadus morhua otoliths was studied. Samples were taken from two time periods, representing low and high temperature regimes. Opaque zones were laid down between January and June, in contrast with the pattern described in other published studies. Translucent zone formation started earlier in the warmer period, corresponding to peak annual sea surface temperatures, and a period of slow body growth and low metabolic activity. Translucent zone formation, however, continued once temperatures decreased and growth rate increased. It is hypothesized that translucent zone formation is triggered at a threshold of metabolic stress, and that the combined energetic requirements of reproduction, growth and migration may maintain translucent zone formation even if feeding conditions improve. Higher temperatures had a significant negative effect on the rate of translucent zone deposition, but caused a slight increase in opaque zone formation rate. The findings of this study indicate that historical otolith collections could provide key inputs into future phenological studies to improve the understanding of climate change impacts and the dynamics of otolith structure.

Age, growth, and reproductive biology of the blackbelly rosefish from the Carolinas, U.S.A.

Otoliths and gonads of blackbelly rosefish Helicolenus dactylopterus dactylopterus were collected from the commercial fishery off the Carolinas in 1994–1997. Opaque bands on transverse sections of otoliths were determined to be annuli by analysis of marginal increments. Opaque zone formation occurs between July and January. Ages ranged from 7 to 30 years. Blackbelly rosefish have intraovarian gestation. Fertilization is internal, as free spermatozoa were found primarily in resting ovaries from July through early December with peak occurrence in September through November. There was a delay of 1–3 months before fertilization, as oocyte development did not begin until December. Occurrence during January through April of early‐celled embryos, the most advanced stage observed, and postovulatory follicles indicated that oocyte development was rapid. Egg development occurs in a clear gelatinous matrix secreted into the ovarian cavity. The reproductive mode is a zygoparous form of oviparity, intermediate between oviparity and viviparity. Population sex ratio departed markedly from 1: 1 for most length intervals. Males were more abundant at lengths >250 mm LT and the overall male: female ratio was 1 : 0·60.

Growth characteristics in the otoliths of selected South African sparid fish

Growth characteristics in the otoliths of several South African sparid fish (Diplodus sorgus copensis, D. cervinus hottentotus, Chrysoblephus laticeps, Cymotoceps nasutus, Pochymetopon grande, Rhobdosargus holulbi and Sparodon durbonensis) were investigated. The micro-incremental pattern of deposition in the otoliths conformed to the general pattern of otolith structure described in the literature. Sparid otoliths consist of a central opaque nuclear region, composed of a nucleus and multiple accessory primordia. Daily increments surround the nuclear region, which decrease in width as the distance from the nucleus increase. At the macroscopic level, under transmitted light, narrow opaque and wide translucent annual growth zones were identified in sectioned otoliths. Scanning electron microscope analysis of the annual growth zones revealed that the micro-increments within the opaque zones are narrowly spaced with prominent discontinuous phases (D-zone). This results in a higher protein content and greater optical density of the zone. The translucent zones are composed of widely spaced, daily increments with prominent incremental phases (L-zone), accounting for the translucent nature of this zone. Opaque-zone formation was shown to be indicative of slow growth and was correlated with periods of reproductive activity in some of the species studied. The translucent zone is formed after the spawning season and represents fast growth.

耳石によるニギス産卵系群の分離の可能性

The possibility of race separation for nigisu, Glossanodon semifasciatus (KISHINOUYE), was demonstrated and its biological implications were discussed. The otolith of nigisu showed various types, based on differences occurring in the appearance of the hyaline of opaque first growth zone, and the width of the hyaline band. The appearance of these considerable variations in the otolith type were suggested as being due, in the main, to differing seasonal growth conditions during the larval and post-larval periods. The early spawners might develop a wide hyaline zone as the first growth mark and the late spawners a narrow hyaline zone. However, if a fish is spawned at the time of the opaque zone formation, the otolith will have an opaque type of first growth region. Some differences in the growth rate between the early and the late spawning groups were estimated for each age or year class. The differences between the two groups were greater in the zero age-class than in older classes, and decreased with age.

魚貝類の石灰化に関する研究-VII

The protein concentration and distribution of the protein fractions of the otolith fluid (endolymph of the sacculus) were determined seasonally by the micro-Kjeldahl method and by paper and cellulose acetate electrophoresis, using three types of fish, flatfish, goldfish and rainbow trout, which have differing otolith characteristics. (1) The otolith fluid was successfully collected from the sacculus by use of a fine glass capillary. The average amount of this fluid collected from one medium-sized individual was about 15 μl in flatfish, 1 μl in goldfish, and 7 μl in rainbow trout. (2) An additional fraction of prealbumin was found to occur seasonally in the otolith fluid of both flatfish and goldfish at a certain time corresponding to the period of opaque zone formation in their otoliths, while such a seasonal occurrence of a prealbumin fraction was not detected electrophoretically throughout the year in the otolith fluid of rainbow trout whose otolith is homogeneously glassy, nor in all the sera of the species examined. (3) In the otolith fluid of flatfish, the protein concentration was found to increase seasonally corresponding to the period of opaque zone formation in the otolith, while such a seasonal change of the protein concentration was not found in the otolith fluid of rainbow trout, nor in the sera of both flatfish and rainbow trout. (4) Accordingly, both the seasonal occurrence of an additional prealbumin fraction and the seasonal increase of the protein concentration in the otolith fluid may favor the formation of the organic matrix of the opaque zone in the otolith.