Reproductive biology of shovelnose guitarfish <Emphasis Type="Italic">Rhinobatos productus</Emphasis> from the eastern Gulf of California México |
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Authors: | J Fernando Márquez-Farías |
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Institution: | (1) Centro Regional de Investigación Pesquera de Mazatlán, Instituto Nacional de la Pesca. SAGARPA, Calzada Sábalo-Cerritos S/N, CP. 82010, Mazatlán, Sinaloa, México;(2) Centro de Investigaciones Biológicas del Noroeste, Km. 2.5 Carr. a Las Tinajas, Predio El Tular, Col. Las Tinajas, CP. 85460, Guaymas, Sonora, México |
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Abstract: | Guitarfishes are a primary component of artisanal elasmobranch fisheries and are commonly taken as trawl fishery bycatch throughout
the Gulf of California. However, little is known of the life history of this species. To address this lack of critical biological
information, the reproductive biology of Rhinobatos productus was investigated in the eastern Gulf of California. Development of claspers and testes indicated that males reach maturity
at 53 cm total length (TL). Measurements of oviducal gland, largest ovum diameter, and uterus width indicated that females
>57 cm TL are mature. This species possesses two functional ovaries: the ovarian cycle and gestation run concurrently. Histological
analysis of oviducal glands did not provide evidence of sperm storage, but females carrying uterine capsules were observed
over an extended period, suggesting the possibility of diapause in the early embryonic development. Following 4–5 months of
embryonic growth, pups were typically born from late June to October after a gestation period of approximately 11–12 months.
Width of yolk sac was inversely related to embryo length. The rate of reduction of yolk sac width suggests that embryos depend
on the sac until birth. Mean fecundity was estimated to be 5 (range 1–10, s.d. = 2.24) with a 1:1 sex ratio. Average size
at birth was 175 mm TL. Seasonally, gravid females enter shallow waters for parturition, becoming extremely vulnerable to
gill nets used in the artisanal ray fishery. |
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