Los peces como animales sociales, reproduccion

Chapter 21
Fishes as social animals: reproduction

Chapter contents CHAPTER CONTENTS
Reproductive patterns among fishes, 455 Courtship and spawning, 461 Parental care, 468 Alternative mating systems and tactics, 473 Summary, 475 Supplementary reading, 476

Reproductive patterns among fishes
Important components of a breeding system include frequency of mating, number of partners, and genderrole of average individuals (Table 21.1). Fishes show greater diversity in these traits than do other vertebrates. Most fishes follow the mammalian and avian norm of remaining one gender throughout adult life, but many fish species change sex and some are parthenogenetic, producing young from unfertilized eggs (see Chapter 10, Determination, differentiation, and maturation; Chapter 24, Lifehistories and reproductive ecology). Some fishes retain a single mate, perhaps for life, others mate promiscuously, and a few are haremic. And in some fishes, a single breeding system may not characterize the entire species.

volutionary success is determined by an individual’s ability to place genes in future generations, relative to the success of conspecifics. To transmit genes, individuals must matewith conspecifics. However, many fish species are relatively solitary as adults. During breeding seasons, fish must overcome individualistic habits and seek out potential mating partners. Suitable spawning habitats and substrates must be found or even modified into nests, activities of males and females must be synchronized, and tactics for avoiding hybridization (species isolating mechanisms) shouldbe employed. Aggregations of reproductively active individuals create potential competition for spawning sites and partners, eliciting territorial and mate choice behavior. Courting and spawning may distract the attention of participants and thus make them more vulnerable to predators. After spawning, many species engage in varying degrees of parental care. All these activities and characteristicsconstitute the diverse mating systems of fishes. Our emphasis here will be on the diversity of mating systems, with focus on patterns and adaptations where they can be identified.

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Lifetime reproductive opportunities
Most fishes are iteroparous, spawning more than once during their lives (e.g., sharks, lungfishes, sturgeons, gars, tarpons, minnows, trouts, codfishes, seabasses). However, somewell-known species are semelparous, spawning one time and dying. Semelparity characterizes most salmon of the genus Oncorhynchus (e.g., Pink, Chum, Chinook, Coho, and Sockeye salmon). These fishes hatch in fresh water, migrate to the sea for a period of 1–4 years, and then return to their natal (birth) stream where they spawn and die. Although the life cycle of females appears to be relatively fixedacross a species, intrapopulational
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Part V Behavior and ecology

Table 21.1
A summary of components of breeding systems in fishes, with representative taxa. Accurate categorization is often hampered by the difficulty of following individual fish over extended periods in the wild. Although families are listed for some components, exceptions are common within a family. Modifiedfrom Wootton (1990), used with permission. I. Number of breeding opportunities A. Semelparous (spawn once and die): lampreys, river eels, some South American knifefishes, Pacific salmons, Capelin B. Iteroparous (multiple spawnings): 1. A single, extended spawning season: most annuals (rivulines) 2. Multiple spawning seasons: most species (elasmobranchs, lungfishes, perciforms) Mating system A.Promiscuous (both sexes with multiple partners during breeding season): herrings, livebearers, sticklebacks, greenlings, epinepheline seabasses, damselfishes, wrasses, surgeonfishes B. Polygamous: 1. Polygyny (male has multiple partners each breeding season): sculpins, sunfishes, darters, most cichlids; or polygyny (haremic): serranine seabasses, angelfishes, hawkfishes, humbug damselfishes, wrasses,...