Sexual dimorphism in Sebastes

Abstract

Sexual dimorphism and factors that may cause it were investigated in 34 species of the genus Sebastes. Sexual dimorphism in standard length and morphometric characters are fairly common in rockfish. In many species males are shorter than females. However in males head length, width of orbit, interorbital width, length of upper jaw, longest pectoral fin ray and longest dorsal spine tend to be larger at a specified size than in females. Water-column species tend to be more dimorphic than demersal species. We suggest that the observed differences in dimorphism in standard length may be related to differences in mating and territorial behavior. Dimorphisms in morphometric measurements may be related to compensation in feeding ability for reduced standard length of males, mating and territorial behavior.

Age and growth of the small red scorpionfish, Scorpaena notata Rafinesque, 1810, based on whole and sectioned otolith readings

“…This is in contrast to most other Scorpaeniformes, females being often larger than males (Wyllie Echeverria 1986; Lenarz and Wyllie Echeverria 1991).Generally, it is rather common in fish that a larger size in females increase their fecundity, while the same may not be true in males (Berglund et al 1986). In the case of S. notata, the documented low fecundity (Muñoz et al 2005), compared to other Scorpaeniformes, such as Trigla lyra (Muñoz 2001) or H. dactylopterus (Muñoz and Casadevall 2002), could be the reason of the absence of sexual size dimorphism.…”

Sexual dimorphism in Sebastes owstoni (Scorpaenidae) from the Sea of Japan

“…The greater distance between the pelvic and anal fi ns in females, differing from the other sexually dimorphic characters above, is considered to be related to fecundity and egg volume. Among the sexually dimorphic characters discussed by Lenarz and Wyllie Echeverria (1991), interorbital width, upper jaw length, pectoral fi n length, and longest dorsal fi n spine were not sexually dimorphic in S. owstoni. To further understand the factors related to sexually dimorphic characters, further species examination and detailed ecological studies are needed.…”

“…Wyllie Echeverria (1986) also suggested that males matured younger than females, thereby having a greater number of mating opportunities. However, Lenarz and Wyllie Echeverria (1991) subsequently reported that both sexes matured at the same age in many species, noting that the increased spawning opportunity hypothesis for early maturing males did not hold for all species. Applicability of the foregoing hypothesis to S. owstoni requires an investigation of age, growth, and age of maturity for that species.…”

“…According to Lenarz and Wyllie Echeverria (1991), head length, orbit diameter, interorbital width, upper jaw length, pectoral fi n length, and longest dorsal fi n spine tended to be greater in males than in females in several species of Sebastes. They regarded such differences in morphometric characters as being related to compensations in feeding ability for the reduced SL of males and mating behavior: viz., head length, interorbital width, and upper jaw length related to maximum food item size; orbit diameter related to the ability to detect food items; pectoral fi n length and longest dorsal fi n spine related to swimming ability, particularly maneuverability while feeding; and relatively great fi ns and orbits related to mating behavior by suggesting greater size.…”

“…3), a common feature of Sebastes species (Wyllie Echeverria, 1986;Lenarz and Wyllie Echeverria, 1991). Size dimorphism may be attributed to larger females being capable of producing and accommodating large numbers of embryos, as discussed by Wyllie Echeverria (1986).…”