Francisco Cerna

Age and growth of the shortfin mako (Isurus oxyrinchus) in the south-eastern Pacific off Chile

The shortfin mako, Isurus oxyrinchus, is a large pelagic shark with a widespread global distribution. However, very little is known about most aspects of this species for the south-eastern Pacific. In the present paper, the age and growth parameters of the shortfin mako, caught by Chilean swordfish longline fisheries from 2004 to 2005, are reported. Ages were estimated by counting band-pairs from sections of vertebral centra from 547 individuals, ranging from 76 to 330 cm in total length (TL). Trends in the proportion of opaque edges for all ages combined and grouped into ages 0-6 and 7-26 years indicated that they are formed during summer and showed that annually, one band-pair is formed in the vertebrae of shortfin makos. Modal-progression analysis was used to verify the first three age classes (ages 0-2 years). For both sexes, the oldest estimated age was 25+ years. Von Bertalanffy growth parameters were estimated at L∞ = 325.29 cm TL, K = 0.076 year −1 and t0 =− 3.18 years for females and L∞ = 296.60 cm TL, K = 0.087 year −1 and t0 =− 3.58 years for males. The results indicated that this species is highly vulnerable to exploitation and, thus, urgent conservation measures are required.

Parallel decadal variability of inferred water temperatures for Northern and Southern Hemisphere intermediate water masses

We use a novel proxy (growth rates of long-lived deep water fish, orange roughy) to reconstruct inferred water temperatures of intermediate water masses in both Northern and Southern Hemispheres since the mid-1800s. The data are consistent with instrumental records showing long-term warming in the Northern Hemisphere but also indicate decadal variability of intermediate depth temperatures that is coherent across the two hemispheres. This variability correlates with the dominant subpolar annular mode in each hemisphere and implies a bihemispheric oceanic response to external forcing that influences the properties of intermediate depth water masses.

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

The Peruvian anchovy (Engraulis ringens) is a resource of considerable economic importance, whose stock unit is distributed between 16°00′S and 24°00′S and is shared between Chile and Peru. In the present study, daily growth patterns of juvenile and adult Peruvian anchovies in northern Chile were determined using micro-increments of sagittal otoliths for the recruitment and fishery seasons of 2009 and 2010. A characteristic feature was the existence of very distinctive daily micro-increments, through which a complete sequence of micro-increments was obtained from the primordium to otolith edge for juveniles (7.5–12-cm total length (TL)) and adults (12.5–18.0cm TL), whose ages were in the range 56–166 and 137–409 days respectively. Hatch dates extended from July 2009 to July 2010, where juveniles recruited to a fishery in a given month were the survivors of a spawning that had occurred approximately 3–4 months before. A Laird–Gompertz model fitted to length-at-age data for juveniles estimated maximum instantaneous growth rates that ranged from 0.98 to 1.57mm day–1, whereas overall mean individual growth rates back-calculated for the age range of juveniles ranged from 0.65 to 1.02mm day–1. The von Bertalanffy seasonal parameters estimated through the entire life history showed high growth, with a growth coefficient K=1.1 and mean length at the first year of 16.3cm TL. Consequently, E. ringens in northern Chile seems to maximize growth in the first year of life.

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

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 and age-at-recruitment of the anchoveta Engraulis ringens as indicated by a multi-annual analysis of otolith microstructure across developmental stages

The anchoveta (Engraulis ringens) plays a key role in the ecology of the Humboldt Current System and is of major economic importance; however, many aspects of its early life history are still poorly understood. In this study, an analysis of daily age and length patterns was carried out using the sagittal otoliths from wild larvae (0-0.2 cm standard length, LS ), pre-recruits (3-6 cm total length, LT ), recruits (7-12 cm LT ) and young adults (12-15 cm LT ). Additionally, variability in growth and age at recruitment (AR ) were evaluated for recruits caught in northern Chile in 1973, 1982, 2009, 2010, 2012, 2013, 2014 and 2015. The age-length relationship showed four allometric patterns that were well described by Laird-Gompertz models. The absolute growth rates at the inflexion point (GAR ) were 0.56, 0.75, 1.22 and 1.16 mm d-1 for larvae, pre-recruits, recruits and young adults, respectively. At the interannual scale, GAR values were always >1 mm d-1 (mean ± S.D. 1.37 ± 0.21 mm d-1 ; range 1.12-1.64 mm d-1 ), irrespective of the season of hatching (i.e. winter v. spring); additionally, in most cases, GAR values were reached before the second month of life (mean ± S.D. 50.47 ± 9.73 days) at c. 4 cm LT (mean ± S.D. 4.22 ± 0.29 cm). Mean AR was < 150 days (112 ± 29 days; range 75-149 days); in contrast, estimates of AR were higher and growth rates were lower in 1973, 1983 and 2000. These results demonstrate very fast growth and early AR of anchoveta in northern Chile, suggesting most fish are removed by the fisheries at very early ages. An evaluation of the implications of these results on stock assessment and management of this species is highly recommended.