Journal of Applied Ichthyology J. Appl. Ichthyol. 31 (2015), 718–723 Received: July 1, 2014 © 2015 Blackwell Verlag GmbH Accepted: February 14, 2015 ISSN 0175–8659 doi: 10.1111/jai.12802 Reproductive biology of female cardinalfish, Epigonus crassicaudus de Buen, 1959 By A. Flores1, R. Wiff2,3,E.Dıaz4 and P. Ga´lvez5 1Colombia, Santiago, Chile; 2Center of Applied Ecology and Sustainability (CAPES), Pontificia Universidad Catolica de Chile, Santiago, Chile; 3Copas Sur-Austral, Departamento de Oceanografıa, Universidad de Concepcion, Concepcion, Chile; 4Division de Investigacion Pesquera, Instituto de Fomento Pesquero, Iquique, Chile; 5Division de Investigacion Pesquera, Instituto de Fomento Pesquero, Valparaıso, Chile Summary et al. (2000) and Cubillos et al. (2009) reported on maturity The cardinalfish (Epigonus crassicaudus) is a long-lived and ogives in this species; both reproductive studies showed sig- endemic deep-water fish inhabiting the central and southern nificant differences between estimates of length at 50% of coast off Chile. Knowledge about basic biological attributes maturity. These differences can be explained by differences in including maturity aspects is fragmentary in this species. The spatio-temporal coverage of the fish sampled and the matu- historical and comprehensive data available are applied to rity scale used in the two studies. These drawbacks in the provide a detailed study of the reproductive biology of the maturity ogives available for the cardinalfish preclude any female cardinalfish. The gonadosomatic index was computed firm conclusion concerning reproduction in this species, thus from 5110 female gonads collected by onboard scientific a comprehensive analysis of its reproductive biology is desir- observers between October 2000 and December 2012. A total able. The main aim of this work therefore was to provide a of 1467 females gonads collected between March 2007 and detailed study of the reproductive biology of cardinal- December 2009 were subjected to histological analysis of fish using the extensive data available from the fishery- maturation upon which a maturity ogive was estimated. The monitoring program collected by the Instituto de Fomento ovarian development of this specie is asynchronous, charac- Pesquero (IFOP-Chile). terized by a continuous reproductive cycle in which repro- ductive activity is found throughout the year with a Materials and methods maximum during the austral autumn and summer (between May and June). Length at 50% maturity was estimated in A total of 5110 female cardinalfish were collected monthly 23.2 cm of fork length (95% CI: 21.7–23.9 cm). The results between October 2000 and December 2012 off central Chile, ° 0 ° 0 presented here are compared with previous sparse estimates covering an area between 29 00 S and 42 00 S. Data regard- available for this species. ing fork length (FL, cm), total weight (TW, g), gutted weight (GW, g), and ovary weight (OW, g) were collected randomly from each fishing haul by scientific observers onboard. Ova- Introduction ries were assigned to a macroscopic maturity stage according Cardinalfish Epigonus crassicaudus (de Buen, 1959) is a fish to the scale defined for cardinalfish: Virginal (Stage 1), characterized by its mesobenthic/pelagic habits. This is an Immature (Stage 2), Maturation (Stage 3), Maturation with endemic species along the Chilean coast distributed mainly Recent Spawning (Stage 4), Spawning (Stage 5), and Spent between 29°000S and San Pedro bay (42°500S) in depths of (Stage 6). between 200 and 400 m (Wiff et al., 2008). Fishing opera- A total of 1467 female gonads were collected between tions targeting cardinalfish ceased after 2010; the most March 2007 and December 2009. Samples were fixed in 4% recent stock status labeled this species as depleted (Galvez buffered formaldehyde and then processed for histological et al., 2010; Tascheri et al., 2012). Late introduction of analysis. Slices of 3 mm gonad tissue were embedded in l annual quotas in 2003, high uncertainty in stock assess- paraffin; 5 m thick sections were stained with Harris’s hae- ments, as well as caveats regarding the knowledge of matoxylin and eosin. Gonadal development stage was demography and population dynamics including that of assessed according to the histological maturity scale for car- maturity, have been proposed as the main causes underly- dinalfish (Table 1). In addition, oocyte sizes were recorded ing the collapse of this fishery in Chile (Tascheri et al., by disaggregating, using water pressure on a sieve l 2012). (250 m), and then digitalized using a scanner on a grey Currently, only basic knowledge for cardinalfish on growth scale with a resolution of 800 dpi. Oocytes were then auto- (Galvez et al., 2000; Cubillos et al., 2009; Ojeda et al., 2010; matically counted and measured using IMAGEJ v.1.34s Contreras-Reyes and Arellano-Valle, 2013), natural mortality (http://rsb.info.nih.gov/ij/). (Cubillos et al., 2009; Tascheri et al., 2012) and maturity The gonadosomatic index (GSI) was computed as the ratio (Galvez et al., 2000; Cubillos et al., 2009) is available. Galvez between ovary weight (OW) and gutted weight (GW) as: U.S. Copyright Clearance Centre Code Statement: 0175-8659/2015/3104–718$15.00/0 Reproductive biology of cardinalfish 719 Table 1 (a) (b) Maturity stages of E. crassicaudus female gonads according to the histological scale in Galvez et al. (2010) Stage Terminology Histological criteria 1 Virgin Presence only of previtelogenic oocytes of chromatin nuclear type. Oocyte sizes up to 228 lm 2 Immature Presence of three types of oocytes: chromatin-nucleolus, perinucleolar and cortical alveoli. Oocyte sizes up to 300 lm 3 Early Presence of advanced cortical alvioli maturing oocytes, beginning the incorporation of (c) (d) eosinophilic yolk granules partially occupying the cytoplasm. Oocyte sizes up to 500 lm 4 Late Oocytes with large yolk globules and maturing germinal vesicle (GV) in the cytoplasm surrounded by several coalescent oil droplets. Mature oocytes up to 600 lm 5 Mature Oocytes completely yolked and migration of GV toward the animal pole. Oocyte sizes up to 700 lm 6 Ripe or Mature oocytes with cytoplasm completely hydrated fused and homogeneity of yolk and beginning of hydration. Most advanced (e) (f) oocytes above 750 lm 7 Spawning During ovulation, postovulatory follicles and hydrated oocytes observed 8 Partial post- Presence of yolked oocytes and spawning postovulatory follicles (PFO) in different reabsorption phases 9 Spent PFO and yolked oocytes (non-ovulated) undergoing atresia. Parenquime shown with previtelogenic oocytes OW GSI ¼ Â 100 (g) (h) GW To validate the independence between GSI and individual size, we used a log-log scale to linearize the power function between OW and GW (model selected by residual analysis) and then evaluated isometry by testing the slope of this rela- tionship being significantly different than 1 using a T-test (Somarakis et al., 2004). We also evaluated homogeneity by testing how similar these slopes were among different matu- rity stages by using covariance analyses (DeVlaming et al., 1982; Erickson et al., 1985). (i) (j) The reproductive cycle, GSI, and the proportion of active mature females (PAM) were modelled using Generalized Additive Models (GAM) following Wood (2006). Females achieving stages 3–5 in the macroscopic scale were classified as active mature. The GAMs used a two-dimensional tensor product by month and length strata as a covariate. Model selection for GSI and PAM was performed using generalized cross validation (GCV) and an unbiased risk estimator (UBRE), respectively (Wood, 2006). Fish that had reached at least stage 3 in the histological scale were classified as mature. Only gonads collected Fig. 1. Histological and frequency distributions of oocyte sizes of E. crassicaudus in different developmental stages. CN, chromatin-nu- between the beginning and the peak of the main reproductive cleolu; PO, perinucleolar oocyte; CA, cortical alveoli; EY, early yol- season were considered for estimation of the proportion of ked; AY, advanced yolked; GVM, germinal vesicle migration; H, = µ mature female at length, PL using a logistic function: hydrated. Scale bar 250 m 720 A. Flores et al. sizes once the ovaries have reached maturity (stage ≥ 3). ¼ 1 PL ðb þb Þ 1 þ e 1 2L When the ovary reaches the initial phase of vitellogenesis (stage 3) the oocyte increases in size, displacing the mode b b where 1 and 2 are the parameters estimated using maximum of distribution as the yolk continues accumulating in the likelihood considering a binomial error distribution (Welch cytoplasm (see stage 4). Stage 5 was characterized by a and Foucher, 1988). Uncertainty was incorporated into the mode of oocytes with sizes above 600 lm, although it did model using a parametric bootstrap (Roa et al., 1999). not show a clear separation from the rest of the less-devel- Goodness-of-fit was assessed using the Hosmer-Lemeshow test oped oocytes. This only occurs during the hydration phase (HL test), as suggested by Hosmer and Lemeshow (1989). where oocytes reach sizes larger than 750 lm (Fig. 1). This The length at 50% maturity (L50) was computed as: species presented a continuous oocyte development charac- b teristic of fishes with asynchronous ovarian reproductive ¼ 1 L50 b strategy. 2 The linear log-log relationship between ovary weight (OW) All statistical analyses were conducted using R statistical and gutted weight GW was significant (P < 0.05) in all stages software (www.r-project.org). analyzed. The slope of these relationships did not differ sig- nificantly from 1 (P > 0.05), except for stage 6 (Table 2). This indicates isometry between OW and GW in most matu- Results rity stages. In addition, the slopes across maturity stages Histological analysis in Fig. 1 shows the presence of oo- were not significantly different (F = 0.906, P > 0.05), validat- cytes in different phases of development in a wide range of Table 2 Descriptive statistics of log-log relationship between ovary weight (OW) and gutted weight (GW) in E.