A Standardized Terminology for Describing Reproductive Development in Fishes

Abstract

As the number of fish reproduction studies has proliferated, so has the number of gonadal classification schemes and terms. This has made it difficult for both scientists and resource managers to communicate and for comparisons to be made among studies. We propose the adoption of a simple, universal terminology for the phases in the reproductive cycle, which can be applied to all male and female elasmobranch and teleost fishes. These phases were chosen because they define key milestones in the reproductive cycle; the phases include immature, developing, spawning capable, regressing, and regenerating. Although the temporal sequence of events during gamete development in each phase may vary among species, each phase has specific histological and physiological markers and is conceptually universal. The immature phase can occur only once. The developing phase signals entry into the gonadotropin‐dependent stage of oogenesis and spermatogenesis and ultimately results in gonadal growth. The spawning capable phase includes (1) those fish with gamete development that is sufficiently advanced to allow for spawning within the current reproductive cycle and (2) batch‐spawning females that show signs of previous spawns (i.e., postovulatory follicle complex) and that are also capable of additional spawns during the current cycle. Within the spawning capable phase, an actively spawning subphase is defined that corresponds to hydration and ovulation in females and spermiation in males. The regressing phase indicates completion of the reproductive cycle and, for many fish, completion of the spawning season. Fish in the regenerating phase are sexually mature but reproductively inactive. Species‐specific histological criteria or classes can be incorporated within each of the universal phases, allowing for more specific divisions (subphases) while preserving the overall reproductive terminology for comparative purposes. This terminology can easily be modified for fishes with alternate reproductive strategies, such as hermaphrodites (addition of a transition phase) and livebearers (addition of a gestation phase).

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

“…A macroscopic and microscopic maturity scale of five 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.…”

“…Sections were cut at 5 μm and stained with Harry's haematoxylin followed by eosin counterstain as in González-Castro et al (2011). Histological classification of ovaries was based on oocyte development stage (Brown-Peterson et al, 2011).…”

“…Soon after fixation, 30 ovaries in actively spawning sub-phase (according 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.…”

Reproductive variability of the common snook, Centropomus undecimalis, in environments of contrasting salinities interconnected by the Grijalva–Usumacinta fluvial system

“…The macroscopic stages of gonadal maturity were defined following the criteria of Brown- Peterson et al (2011), considering the following phases: (I) immature, fish that never spawned; (II) developing, fish with growing gonads but not ready to spawn; (III) spawning capable, fish with a completely developed gonad that could spawn during the cycle, including the actively spawning subphase for those found spawning; (IV) regressing, cessation of spawning; and (V) regenerating, sexually mature fish that are reproductively inactive. The total length at which 50% (L 50 ) of the specimens actively play a role in reproduction was calculated following Vazzoler (1996), using the accumulated frequency of reproductive stages for each size interval and adjusting it to a logistic function, according to the suggestions of Gayanilo and Pauly (1997).…”

“…Las etapas de madurez gonádica fueron definidas siguiendo el criterio de Brown- Peterson et al (2011), considerando las siguientes etapas: (I) inmadura, peces que nunca han desovado; (II) en desarrollo, peces con gónadas en crecimiento pero que no están listos para el desove; (III) capaz de desovar, peces con una gónada completamente desarrollada que puede desovar durante la temporada, e incluye la subetapa desove activo para los que se capturaron desovando; (IV) en regresión, peces que han terminado de desovar; y (V) en regeneración, peces sexualmente maduros pero reproductivamente inactivos. Para determinar la LT a la cual el 50% (L 50 ) de los ejemplares participa activamente en la reproducción, se emplearon los cálculos propuestos por Vazzoler (1996), utilizando la frecuencia acumulada de las etapas de madurez para cada intervalo de talla y ajustada a la función logística de acuerdo con lo sugerido por Gayanilo y Figura 1.…”