Validation of daily microincrement deposition in otoliths of juvenile and adult Peruvian anchovy Engraulis ringens

Abstract

Wild adult specimens of the Peruvian anchovy Engraulis ringens were captured and reared to validate the daily periodicity of otolith microincrement formation. The postcapture stress generated spontaneous spawning, making it possible to conduct a rearing trial on larvae first in an artificial nutrient-enriched system (ANES) for 52 days followed by an artificial feeding regime in a culture tank until day 115 post-hatch. Microincrements of the sagittal otoliths of sacrificed juveniles [mean ± S.D. total length (LT ) = 5·13 ± 0·37 cm, range 5-6 cm; c.v. = 7·5%] showed very distinct light and dark zones. The slope of the relationship between the total number of increments after the hatch check and days elapsed after hatching was not significantly different from 1. The transfer from ANES to the artificial feeding regime induced a mark in the sagittal otoliths. The number of microincrements after this induced mark coincided with the number of days elapsed after the transfer date. In parallel experiments, adult E. ringens (mean ± S.D. LT = 14·92 ± 0·55 cm, range 13-16 cm) were exposed to one of two fluorescent marking immersion treatments with either alizarin red S (ARS; 25 mg l(-1) per 6 h) or oxytetracycline hydrochloride (OTC; 200 mg l(-1) per 10 h). The microincrements between fluorescent bands were distinct, ranging from 0·89 to 2·75 µm (mean ± S.D. =1·43 ± 0·28 µm; c.v. = 32%) and from 0·71 to 2·89 µm (1·53 ± 0·27 µm; c.v. = 35%) for ARS and OTC, respectively. The relationship between the number of microincrements between marks and the number of elapsed days for ARS and OCT treatments indicated that there was a significant correspondence between the number of increases observed and the number of days. Hence, daily microincrements of otoliths of E. ringens are likely to be formed in juveniles and adults under natural conditions.

Daily growth patterns of juveniles and adults of the Peruvian anchovy (Engraulis ringens) in northern Chile

“…Cermeño et al (2008) concluded that GBR was the most reliable ageing procedure for E. encracicolus. Conversely, Plaza and Cerna (2015) reported a closer correspondence between daily age and number of increments when double rings were counted separately in juvenile E. ringens produced under rearing conditions, although double rings were restricted only to the transition zone (i.e. Zone B) and consequently age underestimation was marginal.…”

“…However, under rearing conditions, the identification of micro-structural zones in E. ringens was very distinctive (Plaza and Cerna 2015) compared with otolith microstructure of wild juveniles where boundaries between zones are not easily identified. Hence, the use of GBR is far more consistent for the identification of primary micro-increments in wild specimens.…”

“…In some areas of the otoliths, subdaily and double rings encompassed wider micro-increments and these were counted as PMs (Fig. 2) following the criteria of Plaza and Cerna (2015), which consisted of applying the bipartite reading criterion (BRC), where each micro-increment comprising a double structure was quantified as a single ring. All counting and measurements of PMs were performed twice for each otolith by two independent readers using the 'manual tag' 'calliper' tools available in the software image analysis program Image-Pro Plus (Media Cybernetics, Inc., Bethesda, MD, USA) at magnifications of 400Â and 1000Â.…”

“…The total age of juveniles and adults was determined on the basis of mean counts of PMs from two replicates (made by the two independent readers); when counts differed by more than 5%, the sample was rejected. The number of PMs was regarded as daily age because the daily periodicity of increment formation was validated in juveniles (5-6 cm TL) and adults (13-16 cm TL) for this species by Plaza and Cerna (2015) through a rearing experiment where fish were exposed to marking immersion treatments with alizarin red S and oxytetracycline hydrochloride. The relationship between the number of micro-increments between fluorescent marks and the number of elapsed days indicated that there was a significant correspondence between the number of increases observed and the number of days.…”

A first experience of Patagonian sprat Sprattus fuegensis spawning in captivity: Adult acclimation, egg and larval measurements

“…Previous experiences with other species indicate that, given suitable reproductive conditions, the stress of being caught may trigger spontaneous spawning in adults within 24 h of capture (Cleary et al 2002, Plaza & Cerna 2015. Because the catches occurred during the reproductive period peak for Patagonian sprat (Leal et al 2011), it was expected that the specimens would have spawned spontaneously within the first day in captivity.…”