Reproduction of Brevoortia aurea (Spix & Agassiz, 1829) (Actinopterygii: Clupeidae) in the Mar Chiquita Coastal Lagoon, Buenos Aires, Argentina

Abstract

Reproductive biology of the Brazilian menhaden, Brevoortia aurea (Clupeiformes), was studied in Mar Chiquita Coastal Lagoon. Its abundance was analysed in relation to environmental variables, and the main biological-reproductive parameters were estimated: size at first maturity, batch and relative fecundity, frequency distribution of oocyte diameters and gonadosomatic index (GSI). Moreover, its reproductive cycle was analysed histologically. Samples were collected from May 2012 to April 2013. Once the spawning period was detected, extra samples were added (October and November 2013). The specimens were caught with gillnets, at a distance of 2,300 meters from the mouth of the lagoon. The highest abundances were observed in the months of October and November. Both macroscopic and microscopic analysis allowed to confirm that in these months the saraca spawn in the area mixo-eurihaline of the lagoon. Females were recorded in the five phases of ovarian development. Histological and frequency distribution of oocyte diameters characterized this species as a batch spawner with undetermined fecundity. The fecundity varied between 19,900 and 178,508 oocytes/female. Relative fecundity ranged between 41 and 381 oocytes/g female ovary free. The size at first maturity was estimated on 277 and 265 mm total length for females and males, respectively.

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Neotropical Ichthyology, 14(1): e150064 Journal homepage: www.scielo.br/ni
DOI: 10.1590/1982-0224-20150064 Published online: xx Month xxxx (ISSN 1982-0224)
1
Reproduction of Brevoortia aurea (Spix & Agassiz, 1829)
(Actinopterygii: Clupeidae) in the Mar Chiquita Coastal Lagoon,
Buenos Aires, Argentina
Nicolás Agustín Lajud1, Juan Martín Díaz de Astarloa1,2 and Mariano González-Castro1,2
Reproductive biology of the Brazilian menhaden, Brevoortia aurea (Clupeiformes), was studied in Mar Chiquita Coastal
Lagoon. Its abundance was analysed in relation to environmental variables, and the main biological-reproductive
parameters were estimated: size at rst maturity, batch and relative fecundity, frequency distribution of oocyte diameters
and gonadosomatic index (GSI). Moreover, its reproductive cycle was analysed histologically. Samples were collected from
May 2012 to April 2013. Once the spawning period was detected, extra samples were added (October and November
2013). The specimens were caught with gillnets, at a distance of 2,300 meters from the mouth of the lagoon. The highest
abundances were observed in the months of October and November. Both macroscopic and microscopic analysis allowed to
conrm that in these months the saraca spawn in the area mixo-eurihaline of the lagoon. Females were recorded in the ve
phases of ovarian development. Histological and frequency distribution of oocyte diameters characterized this species as
a batch spawner with undetermined fecundity. The fecundity varied between 19,900 and 178,508 oocytes/female. Relative
fecundity ranged between 41 and 381 oocytes/g female ovary free. The size at rst maturity was estimated on 277 and 265
mm total length for females and males, respectively.
Se estudió la biología reproductiva de la saraca, Brevoortia aurea (Clupeiformes), en la Laguna Costera Mar Chiquita.
Se analizó su abundancia, en relación con las variables ambientales y se estimaron los principales parámetros biológico-
reproductivos: talla de primera madurez (longitud total), fecundidad parcial y relativa, distribución de frecuencias de
diámetros oocitarios e índice gonado-somático (IGS). Además, se analizó su ciclo gonadal desde un aspecto histológico, en
función de un ciclo anual. Las muestras se colectaron desde Mayo 2012, hasta Abril 2013. Una vez detectado el período de
desove se duplicó el muestreo durante dichos meses (Octubre y Noviembre 2013). Los ejemplares se capturaron con redes
de enmalle, a 2.300 metros de la desembocadura de la laguna con el mar. Las mayores abundancias se observaron en los
meses de Octubre y Noviembre. Tanto el análisis macroscópico como el microscópico permitieron armar que en dichos
meses la saraca realiza desoves en la zona mixo-eurihalina de esta laguna. Se registraron hembras en las cinco fases del
desarrollo ovárico. Los análisis histológicos y de distribución de la frecuencia de diámetros ovocitarios caracterizaron a
esta especie como un desovante parcial con fecundidad indeterminada. La fecundidad parcial varió entre 19.900 y 178.508
oocitos/hembra. La fecundidad relativa varió entre 41 y 381 oocitos/gr hembra libre de ovario. La talla de primera madurez
se estimó en 277 y 265 mm de longitud total para hembras y machos, respectivamente.
Keywords: Clupeiformes, Multiple spawner, Pelagic, Reproduction.
1Laboratorio de Biotaxonomía Morfológica y Molecular de Peces (BIMOPE). Instituto de Investigaciones Marinas y Costeras, IIMyC-
CONICET- UNMdP. Mar del Plata, Buenos Aires, Argentinga. (NAL) nicolaslajud@gmail.com
2Consejo Nacional de Investigaciones Cientícas y Técnicas (CONICET). (JMDA) astarloa@mdp.edu.ar, (MGC) gocastro@mdp.edu.ar
(corresponding author).
Introduction
Members of Clupeidae are typically marine, coastal
and schooling shes, found in all seas from 70° N to
about 60° S (Carpenter, 2002). Some species tolerate low
salinities, sometimes entering fresh water to feed. Clupeids
typically form large schools and generally scatter pelagic
eggs that hatch planktonic larvae (Munroe & Nizinski,
2002). The species of the genus Brevoortia constitute
important sheries and ecological representatives both,
on the northwest and southwest Atlantic Oceans (Deegan,
1993; Forward et. al., 1996; Vaughan, 2007). Historically,
the existence of two large-scaled Southwestern Atlantic
menhaden Brevoortia aurea (Spix & Agassiz, 1829) and B.
pectinata (Jenyns, 1842) have been reported to be occurring
from state of Rio Grande do Sul (Brazil) to the Río de la
Plata estuary (Whitehead, 1985; Lasta & Ciechomski,
1988). However, Cousseau & Díaz de Astarloa (1993),
Segura & Díaz de Astarloa (2004) and García et al. (2008)
concluded that B. aurea (locally called as “saraca”) is the
only species of the genus inhabiting the Southwestern
Atlantic Ocean.
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Brevoortia aurea is an estuarine-dependent, pelagic,
coastal species, inhabiting shallow nursery areas for
their early development, which is capable to perform
migrations between the sea and estuaries (Cousseau &
Díaz de Astarloa, 1993; González-Castro et al., 2009a;
Cousseau et al., 2011). As a lter feeder, the species
has a key position between the primary producers and
the secondary consumers on the trophic chain. High
densities of Brazilian menhaden eggs and larvae have
been documented (Bruno et al., 2013) when the spawning
events take place, as well as high densities of juvenile
when the recruitment occur in estuaries (Gonzales-Castro
et al., 2009a). Also, B. aurea could lend an important role
in the exchange of organic matter between the freshwater
environment and the sea, as B. patronus Goode, 1878 does
in the Northewestern Atlantic (Deegan, 1993; Garman &
Macko, 1998). This fact could bring more importance to
B. aurea resource, in order to decrease the captures of
other exploited species, and to present an alter native use
of these species on the sh our industries.
The reproductive studies of B. aurea performed in
Argentina are scarce. Fecundity estimations have been
performed on Mar del Plata coast (Cassia et al., 1979) and
the spawning frequency and batch fecundity was estimated
(Macchi & Acha, 2000) for the Rio de la Plata estuary. So
far, no studies related to the life cycle (based on monthly
samples during an annual cycle) of adults specimens of
this species, have been carried out in Argentina.
Fish composition of Mar Chiquita has been widely
studied and is well known that this lagoon has a crucial
role in the life cycles of many sh species, as a scale
on migratory routs, refugee from storms, feeding and
nursery area of some commercially and ecologically
important species, as well as exotic invasive species
(González-Castro et al., 2009b, 2013, 2015). From a total
of 28 reported sh species, B. aurea represented the
most abundant species in Mar Chiquita coastal lagoon
(González-Castro et al., 2009a). High densities of B.
aurea specimens in the inner zone of Mar Chiquita lagoon
were correlated with mature/ripe ovaries, as revealed by
sexual maturity stage analysis. This strongly suggests that
reproductive events should occur in the northern zone of
Mar Chiquita. However, these observations were analyzed
only macroscopically and no reproductive studies, related
to the life cycle of the adult stock based on an annual
cycle have previously been carried out for this species.
Moreover, neither estimations of size at rst maturity nor
monthly GSI mean values have been previously reported
for this species.
In this context, the main aim of the present paper
was to study the life cycle of B. aurea in a shallow
estuarine environment, the Mar Chiquita Coastal Lagoon
(Argentina). We tested the hypothesis that B. aurea
reproduce within Mar Chiquita coastal Lagoon. Our
objectives were: (1) to analyze the monthly abundance
and their relationship with environmental variables, (2)
to perform histological analysis of ovarian development
and describe the stages of oocyte development and (3)
to estimate the main biological-reproductive parameters
for the stock of B. aurea that inhabits Mar Chiquita
lagoon (frequency of oocyte diameter distribution, batch
fecu n dit y, leng t h at rst ma t u r ity (L50) and gonadosomatic
index).
Material and Methods
Study area. Mar Chiquita Coastal Lagoon (37º32’S,
57º19’W, Argentina) is a shallow estuary (0.4-3 m deep)
of 25 km large and 5,850 ha, separated from the sea by
a littoral line of dunes, and connected to it by an inlet
channel (Isla, 1995). It is considered a World Biosphere
Reserve by the Man and Biosphere Program (MaB) of
UNESCO (Iribarne, 2001). The semidiurnal tidal regime
affects both depth and salinity in the lagoon. Mean depth
is 1.20 m, with a maximum of 4.90 m at high tide and a
minimum of 0.80 m at low tide. Salinity has a horizontal
gradient that uctuates between 0 and 36, depending on
tide and wind (Reta et al., 2001). Water temperature varies
m o nt hl y an d tw o se as o ns ca n b e id en ti e d: th e wa r m s e as o n
(October to March), with water temperatures between 13
and 21°C, and the cold season (April to September), with
temperatures between 6 and 13°C (Cousseau et al., 20 01;
Reta et al., 2001).
Fish samples. Specimens of B. aurea were collected
monthly between May 2012 and April 2013 in the inlet
channel of the lagoon (Fig. 1). Voucher specimens (UNMdP
2332 and UNMdP 2333) were deposited in the Fishes
Collection of the Instituto de Investigaciones Marinas
y Costeras (IIMyC; CONICET- UNMDP), Argentina.
Once detected the reproductive period of this species,
extra samples were added on October and November 2013
in order to increase the number of samples used for the
reproductive parameters estimation.
Four 25 m long, 1.5 m high monolament gill nets,
with 51 mm, 68 mm, 120 mm and 130 mm mesh sizes were
employed. Environmental variables (water temperature
(°C), salinity (practical salinity units (psu)), and turbidity
(nephelometric turbidity units (ntu)) were recorded
with an Horiba® multiparameter. The specimens were
taxonomically identied following Cousseau et al. (2011)
and Cousseau & Perrota (2013). Total length (TL) was
recorded to the nearest mm. Total weight (TW) and ovary
weight (OW) were recorded to 0.1 g with an electronic
balance.
A macroscopic and microscopic maturity scale of ve
phases was employed according to Brown-Peterson et al.
(2011), as follows: 1-immature, 2-developing, 3-spawning
capable (which includes a sub-phase of actively spawning),
4-regressing and 5-regenerating. Weighed ovaries were
stored 12 h in Davidson solution, and preserved in ethanol
70° GL for the subsequent laboratory analysis.
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N. A. Lajud, J. M. D. de Astarloa & M. González-Castro
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Fig. 1. Study area showing the sample station.
Gonad analysis. A piece of tissue from the stored ovaries
was removed, dehydrated in ethanol 100° GL, cleared in
xylol and embedded in parafn. Sections were cut at 5
μm and stained with Harry’s haematoxylin followed by
eosin counterstain as in González-Castro et al. (2011).
Histological classication of ovaries was based on oocyte
development stage (Brown-Peterson et al., 2011).
Oocyte diameter frequency distribution. Soon after
 x a t i o n, 30 ova ri e s i n ac t ive l y sp a w ni ng su b -p h a s e (a cc o r d i ng
to Brown-Peterson et al., 2011) were stored in ethanol 70°
GL. A total of 200 oocytes per ovary were removed, placed
in water, and the longest axis was measured with an ocular
micrometer. The oocyte diameter frequency was plotted.
Fecundity estimation and Gonadosomatic Index
(G SI%) . Batch fecundity (number of oocytes released
per spawning) was estimated employing 34 ovaries in
spawning capable maturation phase (actively spawning
sub-phase), stored in ethanol 70° GL after xation. These
ovaries were characterized by hydrated oocytes and showed
no evidence of recent spawning (no post ovulatory follicles
were observed). Three portions (of approximately 0.1 g) of
the anterior, medial and posterior parts of the gonad were
rehydrated, weighed with an analytical balance (0.0001 g)
and all hydrated oocytes were counted. Batch fecundity
was estimated according to Hunter et al. (1985). Relative
fecundity (number of hydrated oocytes per gram of ovary-
free body weight) was calculated as the batch fecundity
divided by female weight (ovary-free) (Hunter et al., 1985).
The relationship of batch fecundity to total length and total
weight (ovary free); or relative fecundity to total length and
total weight (ovary free), were described using the Pearson
correlation method (Kartas & Quignard, 1984). The GSI
was estimated as the ovary weight divided by body weight
(x 100). It was analyzed in relation to the annual cycle and
maturity phases.
Abundance analysis. Capture per unit effort (CPUE) in
kg/h, was plot against environmental variables. Monthly
sh abundance variability, related with environmental
variables, was analyzed using the generalized linear models
(GLMs) (Venables & Ripley, 2002). The models were built
with the monthly number of captured shes, as the response
variable, and the environmental variables (temperature,
salinity and turbidity), season of the year (summer, autumn,
winter and spring) and the monthly average of GSI, as
independent variables. As data show over dispersion and
many zero values, a negative binomial error distribution and
log link were specied (Crawley, 2005). Model parameters
were obtained by maximizing the maximum likelihood
(Crawley, 2005).
The models were built with each variable mentioned
above and combinations of those variables. Also, a null
model with no variable was built, in order to test the
hypothesis that none of the tested variables had effect on
the observed abundances. The best model was selected, by
using the Akaike Information Criterion (AIC), as the model
with the lowest AIC (Franklin et al., 2001). Each model
was weighed against the others using the Akaike weights,
which gives an estimation of the likelihood of the model’s
t according to the employed data (Anderson et al., 2000;
Franklin et al., 2001; Johnson & Omland, 2004).
Length at rst maturity (L50). The maturity phase of 588
females and 293 males were determined. Individuals were
grouped in 5 mm length classes, and classied as immat ure
(juveniles) (Phase 1) or mature (adults) (Phases 2 to 5).
A logistic model was tted to the proportion of mature
individuals by total length class, using the maximum
likelihood method (Roa et al., 1999).
Results
A total of 633 females and 321 males was collected
during the sampled period, with a size range of 132-420 mm
(mean=328 mm) and 148-403 mm (mean= 291), respectively.
Environmental variables and capture per unit effort
(CPUE). Specimens of B. aurea captured in this study
tolerated wide range of salinities, from almost fresh (0.7 psu)
to full-strength sea water (33 psu). Remarkably, salinity did
not show a seasonal pattern, as well as the turbidity (0.86 to
90.2 ntu, data not shown). Conversely, water temperature
varied seasonally, showing the lowest value in winter (5.35
°C), and the highest one in summer (26.19 °C) (Fig. 2).
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The lowest abundances (estimated by CPUE) were
registered in winter. Particularly, no captures were recorded
in June, July and August. The highest CPUE values were
recorded in October, and November (Fig. 2).
Generalized linear models. Thirteen models were tested
in order to explain the observed abundances (Table 1). The
model involving the water temperature and the GSI was the
best one with an AIC of 37.1, followed by the one involving
the season and the GSI (AIC 39.1). It is noticeable that the
months in which the lowest temperature was recorded were
correlated with the lowest abundance values. In contrast,
the highest temperature values were not correlated with the
highest abundance values.
Fig. 2. Captures per unite effort (CPUE kg/h), temperature
(°C) and salinity (psu) obtained for Brevoortia aurea during
sampled period in Mar Chiquita Coastal Lagoon.
Gonadosomatic index (GSI). The ANOVA test showed
signicant differences for the mean-GSI values for each
ovaric maturity Phase (P=5.34 x 10-4; F= 14.72). The
mean GSI reached its highest values in October (13.9) and
November (12.1) 2013, and gradually decreases with a
minimum mean GSI value of 2.3 in March (Fig. 3).
Fig. 3. Monthly variation of the gonadosomatic index (GSI)
(females only), based on an annual cycle.
Table 1. Competing models for explaining the abundances
of Brevoortia aurea in Mar Chiquita coastal lagoon.
Model AIC df Δ AIC w
~Null 52.5 2 15.4 <0.001
~Temperaturature (Temp) 51.9 3 14.8 <0.001
~Salinity (Sal) 53.9 3 16.7 <0.001
~Turbidity (Turb) 54 3 16.9 <0.001
~Season 42.3 5 5.2 0.0484
~Sal+Turb 55.7 4 18.6 <0.001
~Temp+Sal 52.7 4 15.6 <0.001
~Season+Temp 42.4 65.3 0.0446
~Temp+Turb 53.1 4 16 <0.001
~Temp+Sal+Turb 53.1 5 16 <0.001
~Temp+GSI 37.1 4 0 0.6429
~Season+GSI 39.1 5 1.9 0.2432
~Temp+Sal+Turb+Season+GSI 44.1 8 7 0.0193
Ovarian cycle. Five ovaric phases were recorded. Immature
individuals (Phase 1) were recorded mostly between
February and April. Phases 2 (development) and 3 (spawning
capable) were recorded in almost all sampled months. The
most advanced maturity phase (Active spawning sub-phase)
appears in 20% of the individuals captured in October and
November 2013. The regressing phase appears in October
and November 2013 during the reproductive events, as
expected considering the batch spawning strategy of this
species (Fig. 4). The regenerating phase was observed only
in December, after the registered reproductive events.
Fig. 4. Monthly relative frequency of the different gonadal
development stages observed in females of Brevoortia aurea
on the annual cycle, and the added samples of October and
November for the Mar Chiquita coastal lagoon.
Description of maturity phases and frequency of
occurrence during the sample period. 1). Immature.
This phase is characterized by very small pink ovaries,
with a thin tunic. Only previtelogenic oocytes are present.
This stage was observed in February, March and April; 2).
Development. This phase was found in all of the annual
cycle months, without the winter ones. The ovaries increase
their sizes, the blood vessels, cortical alveoli oocytes and
primary vitelogenesis oocytes become visible; 3). Spawning
capable. The ovaries in yellow, occupy almost one third of
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N. A. Lajud, J. M. D. de Astarloa & M. González-Castro
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the abdominal cavity. Ovarian arteries and its ramications
appear, and the oocytes are macroscopically visible (mostly
yolked oocytes). This phase was observed in all of the
sampled moths. In the Sub-phase, actively spawning the
ovaries occupy approximately the half of the abdominal
cavity, they become highly ramied and in orange color.
The tunic gain turgidity, and the oocytes reach the largest
size (hydrated oocytes, one mm approximately). This phase
was found only in the reproductive month of October and
November; 4). Regressing. The accid ovaries, with gross
tunics, appear in red color because of the blood spill due to
the recent spawning activity. Primary grow, cortical alveoli
and yolked oocytes are present, as well as postovulatory
follicles (POF’s) and atresia. This phase was found in
October and November 2013; 5). Regenerating. The
ovaries, in yellow, decrease their sizes, recover turgidity
and the tunic remains gross. Only primary grow oocytes
and oogonias are present. This phase was observed only in
December.
Stages of oocyte development. During the analyzed
period, the following stages were observed: A-Oogonias,
B-Primary growth oocyte, C-Cortical alveolus stage,
D-Yolked oocytes, E-Hydrated oocytes, F-Atretic follicles
and G-Post-ovulatory follicles (POFs). (Table 2; Fig. 5).
Frequency distribution of oocyte diameters. The size
diameter distribution of formalin preserved oocytes on
actively spawning ovaries was tetramodal (Fig. 6). The
smallest group refers to primary growth oocytes, with sizes
of 50 to 150 µm. The second one was constituted by cortical
alveoli stage oocytes, and ranged between 150 and 350
µm. The third group was composed by the yolked oocytes,
which ranged between 350 and 750 µm and the last one
corresponded to the nal development oocytes (hyaline and
hydrated oocytes) with diameters from 750 to 1,600 µm.
Fig. 5. A: oogonias (arrow) and primary growth (p) oocytes;
B: cortical alveoli stage oocyte (arrow); C: yolked oocytes;
D: hydrated oocytes (arrow); E: details of a yolked oocyte
(r: radiata zone; g: granulosa cells; t: teca cells); F: atretic
follicle (arrow); G: post-ovulatory follicle “0” (arrow); H:
post-ovulatory follicle “1” (arrow). Scale bars: A, E 25 μm;
B, C, F, G, H, 100 μm; D, 250 μm.
Tab l e 2. Descriptions of each stage of oocyte development, atretic and post-ovulatory follicles.
Stage Microscopic characteristic
A. Oogonias Small cells, with approximately 10 μm diameters. Large nucleus of central location, with lax chromatin, surrounded by
scarce basophilic cytoplasm.
B. Primary growth oocytes With a size between 50 to 200 μm, this cells has basophilic cytoplasm and a large nucleus of central location with some
nucleoli at the periphery.
C. Cortical alveolus
With diameters between 200 and 350 μm and a nucleus of approximately one third of the cell diameter. Vesicles located
on the cell periphery, called “cortical alveoli”, characterize this stage. The cytoplasm is basophilic, the radiata zone is
visible (highly eosinophilic), as well as the follicular layer (granulosa and teca cells).
D. Yolked oocytes
Oocytes increased their diameters from 350 to 750 μm. Yolk granules (with eosinophilic afnity) are present in the
cytoplasm due to the exogenous vitellogenesis. Although less frequent, lipid vesicles are observed disperse between
the yolk granules. Radiate zone (highly eosinophilic) and the follicular cells reach their maximum development. The
nucleus continues in central position.
E. Hydrated oocytes
With a size range from 750 to a 1600 μm. Germinal vesicle migration (GVM) and break down (GVBD) of nuclear
membrane are the previous steps to the cytoplasmic hydration, were the cellular size increases notoriously. Hydrated
oocytes displayed an irregular shape, due to the alcohol dehydration performed at the histological procedures.
F. Atretic follicles Disintegration and reabsorption of the oocytes by the follicular cells, from the periphery to the center. Most are observed
at the end of the reproductive cycle and occur mostly on yolked and hydrated oocytes.
G. Post-ovulatory follicles (POFs) After ovulation, the remaining follicular cells form an irregular shape in the ovary tissue. The follicular lumen size
decreased and the degradation increased according to the time since ovulation.
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Fig. 6. Frequency distribution of oocyte diameters (N =
6000 oocytes measured). From black bars to white bars:
Primary growth oocyte, cortical alveoli, yolked oocytes
and hydrated oocytes.
Fecundi t y. Batch fecundity estimates, ranged between
19,900 and 178,508 hydrated oocytes, corresponding to
females with 353 to 357 mm TL, respectively. Unexpectedly,
no signicant r2 and Pearson correlation were found
between the batch fecundity, against TL and the TW ovary-
free values (Fig. 7 A, B).
Relative fecundity estimates ranged between 50 to 381
oocytes per gram of female, for 353 and 357 TL, respectively.
Again, no signicant r2 and Pearson correlation were found
(Fig. 7 C, D).
Length at rst maturity (L50). The L50 estimated values
were 278 mm TL and 266 mm TL for females and males,
respectively. A 100% of maturity was attained at 340 mm TL
and 310 mm TL for females and males, respectively (Fig. 8).
Fig. 8. Proportion of mature individuals observed for each
length classes of Brevoortia aurea. Females (black circles,
dotted line) L50 = 27.77 cm, N = 588. Males (white circles,
solid line) L50 = 26.59 cm, N = 293.
Fi g. 7. A and B: Batch fecundity as a function of total weight (without ovary) and total length, respectively. C and D:
Relative fecundity as a function of total weight (without ovary) and total length respectively.
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Discussion
Fish composition of Mar Chiquita coastal lagoon has
been recently analysed (González-Castro et al., 2009a). The
authors recorded the presence of high densities of B. aurea
in spring/summer correlated with mature/ripe ovaries, as
was revealed by sexual maturity stage analysis performed at
macroscopic level. They suggested that reproductive events
should occur in the northern zone of this lagoon. They found
adult specimens in the four sampled seasons during 2005-
2006, concluding that this species was the most abundant
of Mar Chiquita Coastal Lagoon, representing the 65.0%
of the total number of specimens sampled. Moreover, the
authors found high densities of early juveniles in summer
and autumn. Furhermore, Bruno et al. (2013) reported
high density of eggs and larvae of B. aurea, in Zone I
(sensu González-Castro et al., 2009a), which basically is
the sample site of the present study. Here, B. aurea was
collected in Mar Chiquita lagoon almost every month (with
the exception of June, July and August). During October
and November, males and females in actively spawning
sub-phase (hydrated oocytes) were found, indicating that
reproductive events take place in this lagoon. Similarly,
Cassia et al. (1979) reported that the spawning season of
the Brazilian menhaden in Mar del Plata coast takes place
mainly between October and December.
Although specimens of B. aurea captured in this
study tolerate a wide range of salinities (0.7-33 psu), the
GLM showed that salinity does not explain the registered
abundances. In contrast, temperature with the addition
of the mean monthly GSI, explained 64% of the observed
abundances. This suggests that the highest abundances of B.
aurea adult spe cimens in Mar Ch iquita Lagoon are cor related
with its highest GSI values (which occur from September to
November). Curiously, the highest temperatures were not
positively correlated with highest abundances, as also was
demonstrated for the grey mullet (Mugil liza) (González-
Castro, 2011). Conversely, the lowest temperatures were
correlated with the lowest abundances of B. aurea recorded
for the present paper. Moreover, González-Castro et al.
(2009a) found no records of adults specimens of B. aurea
in the inner zone of Mar Chiquita coastal Lagoon: this
data support the results of the present paper (no records of
adults specimens in winter in the inlet channel of the lagoon
have been found), suggesting that adult specimens migrate
from the lagoon to the sea (between June to August) when
the water temperature decreases below the physiological
tolerance level of the species. Similar results have been
observed by Lopez-Cazorla (1985) for the estuary of Bahía
Blanca, Argentina, where adult specimens enter the bay
in spring to reproduce and migrate offshore at the end of
summer.
Our results indicated that the reproductive events of
B. aurea were performed at temperatures between 15
and 19 °C, and a salinity range from 21 psu to 31 psu.
Macchi & Acha (2000) reported hydrated females at higher
temperatures (19 and 21°C) and lower salinities (10 to 25
psu) than those recorded in the present work. Similarly,
the Atlantic menhaden B. tyrannus presented the highest
percentages of spawning between 17 and 20ºC (Fitzhugh &
Het t le r, 1995).
Frequency distribution of oocyte diameters and
histological analysis evidenced the batch spawning behavior
of this species. All the stages of oocyte development were
found in a single “actively spawning” ovary. Each stage of
oocyte development was correlated with a different modal
group of the analysis.
Batch fecundity values estimated (19,900 to 178,508
oocytes) is quite similar than those estimated by Macchi &
Acha (2000) (20,000 to 130,000 oocytes). These values are
much greater than those of the most important local species
of Clupeiformes with similar reproductive strategies. For
example, batch fecundity estimated of Anchoa marinii
was 749 to 3,207 oocytes, (López et al., 2013). Rodríguez
et al. (2008) reported a batch fecundity of 570-2,026
oocytes for Ramnogaster arcuata specimens. Pájaro et al.
(1997) reported a fecundity of 13,675 oocytes (+/- 856) for
Engraulis anchoita. However, when comparing the relative
fecundity of these species, it is noticeable that B. aurea
presented the lowest values in comparison with those of the
above mentioned species: 41-381 hydrated oocytes per gram
of female (ovary free) for B. aurea, 127-422 oocytes for A.
marinii (López et al., 2013); R. arcuata between 150 and
437 oocytes (Rodríguez et al., 2008) and E. anchoita with
574 oocytes (Pájaro et al., 1997). These differences could be
due to the largest size of the hydrated oocytes of B. aurea
(1000 to 1600 μm in this paper), in comparison with other
local species of Clupeiformes (A. marinii; R. arcuata and E.
anchoita) which are less than 1000 μm (Rodríguez et al.,
2008; López et al., 2013; Pájaro et al., 1997). The size and
number of eggs produced vary greatly among species and
all of these traits have important consequences for survival.
Egg is positively related to the duration of the incubation
period and the size of the larva. The greater amount of
yolk in large eggs provides more total energy for growth,
resulting in larger larvae at hatching and at rst feeding.
This yields several vital benets: 1) larvae emerge with a
better tness of behavioural and physiological capabilities
than less developed larvae from smaller eggs; 2) they
are more resistant to starvation because weight-specic
metabolic rates are lower and bodily energy stores are
greater; and 3) the larval period is shorter (Fuiman, 2002).
Fecundity values showed a great variation between
females of B. aurea of similar lengths of the present study.
Also, no signicant correlation was found between the
fecundity and the variables “weight” and “length”. This fact
was reported by Macchi & Acha (2000) for this species,
but also for other species of Clupeiformes with similar
reproductive strategies (López et al., 2013). The females
used in this work correspond to the asymptote of innity
length, of the growth curve of Lopez-Cazorla (1985).
Therefore, different cohorts are overlapped on similar
PROOFS

Reproduction of Brevoortia aurea
Neotropical Ichthyology, 14(1): e150064
8
lengths classes. Considering that the fecundity is inuenced
by the age (Nikolsky, 1963; Begenal, 1973; Hempel, 1979),
this fact could explain part of the observed dispersion. An
integrative age and fecundity analyses should be necessary
to strongly sustain this hypothesis.
There is no previous estimation of the L50 value for B.
aurea. Cassia et al. (1979) report the minimal length at
maturity for this species as 22.5 cm TL. The present paper
shows the rst estimates of L50 for the species (27.77 cm TL
for females and 26.59 cm TL for males).
In conclusion, these results exposed above strongly
suggest that B. aurea reproduce within the Mar Chiquita
Coastal Lagoon, and that adults specimens occur during all
year long, being scarce during the winter, season in which
the Brazilian menhaden probably migrates to adjacent
coastal waters with higher temperature than those of Mar
Chiquita lagoon. Future studies will be necessary in order
to evaluate the role that plays the marine environment in the
life cycle of this stock.
Acknowledgements
The authors would like to thank: Juliana Giménez
(CONICET) and Alejandro Sicardi, for technical assistance
in the histological procedures; Marcelo Pons, for logistical
support; Julio Mangiarotti (forest guard in the Mar Chiquita
Biosphere Reserve) and the Mar Chiquita coastal lagoon
authorities (Jorge Paredi, Luis Facca, Mónica Iza, Florencia
Celesia and Gladys Eiras). Matias Delpiani, Damian
Castellini, Valeria Gabbanelli and Martin Vazquez for
helping in collecting specimens. This work was supported
by UNMdP 15/E525, EXA 577/2 and UNMdP 15/E619,
EXA 669/14 grants, but also personal funds of MGC.
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PROOFS