Reproduction of <i>Brevoortia aurea</i> (Spix &amp; Agassiz, 1829) (Actinopterygii: Clupeidae) in the Mar Chiquita Coastal Lagoon, Buenos Aires, Argentina

Lajud, Nicolás Agustín; Astarloa, Juan Martín Díaz de; González-Castro, Mariano

doi:10.1590/1982-0224-20150064

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ARTICLES • Neotrop. ichthyol. 14 (01) • 2016 • https://doi.org/10.1590/1982-0224-20150064 copy

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

Authorship SCIMAGO INSTITUTIONS RANKINGS

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 mixo-eurihaline area 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.

Keywords:
Clupeiformes; Multiple spawner; Pelagic; Reproduction

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	6	5.3	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

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 affinity) 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.

Sociedade Brasileira de Ictiologia Neotropical Ichthyology, Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura, Universidade Estadual de Maringá., Av. Colombo, 5790, 87020-900, Phone number: +55 44-3011-4632 - Maringá - PR - Brazil
E-mail: neoichth@nupelia.uem.br

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