Reproduction
The diversity of shore fishes found in the tropical Eastern Pacific is reflected in a wide variety of reproductive habits. The following discussion is intended to give an overview of the most common patterns. More detailed information is available in the scientific literature or semi- popular works such as Thresher's (1984) Reproduction in Reef Fishes.
The great majority of shorefishes treated here are egg layers that employ external fertilisation. Relatively few species (10% of those included in this guide) bear live young that are prepared to fend for themselves at birth. Included in the latter category in our region are most sharks and rays, and, among the bony fishes, the brotulas and two genera of weed blennies.
Most shorefishes use one of two patterns of egg-laying reproduction. Females of many fishes, including the highly visible wrasses and parrotfishes, scatter relatively large numbers of small, positively buoyant eggs into open water where they are summarily fertilised by the male. Fifty-six percent of the species in this CD reproduce in this manner. The spawning event is typically preceded by nuptial chasing, temporary color changes, and courtship displays in which fins are erected. This behaviour is generally concentrated into a short period of the day, often at sundown or shortly afterwards, or is related to the stage of the tidal cycle. This pattern is seen in diverse groups such as lizardfishes, angelfishes, wrasses, parrotfishes, and boxfishes. Typically either pair or group spawning (the latter involving a single female and multiple males) occurs in which the participants make a rapid dash towards the surface, releasing their gonadal products at the apex of the ascent. The fertilised eggs float near the surface and are dispersed by waves, winds, and currents. Hatching occurs within a few days and the young larvae are similarly at the mercy of the elements. Older larvae, however, are good swimmers and have considerable control over their movements. Recent studies of the daily growth rings found on the ear bones (otoliths) of reef fishes indicate that the larval stage generally varies from about 1-8 weeks depending on the species involved. The extended pelagic larval period no doubt accounts for the wide dispersal of many reef species. For example, many fishes that occur in other Indo-Pacific regions have geographic ranges that extend from East Africa to Polynesia or even range further eastward to the Americas.
The second major reproductive pattern (exhibitied by 30.3% of species in our region) involves species that lay their eggs on the bottom, frequently in rocky crevices, empty shells, sandy depressions, or on the surface of invertebrates such as sponges, corals, or gorgonians. Among the best known fishes in this category are the damselfishes, blennies, gobies, and triggerfishes. These fishes often prepare the surface prior to egg deposition by cleaning away detritus and algal growth. Bottom spawners also exhibit elaborate courtship rituals which involve much aggressive chasing and displaying. This behaviour has probably been best studied amongst the damselfishes. In addition, one or both parents may exhibit a certain degree of nest-guarding behaviour in which the eggs are kept free of debris and guarded from potential egg feeders such as wrasses and butterflyfishes. A more specialised mode of parental care is seen in cardinalfishes and sea-catfishes, in which the male broods the egg mass in its mouth. Similarly, male pipefishes and seahorses brood their eggs on a highly vascularised region of the belly or underside of the tail. Only 3.5% of our region's fishes reproduce using brooded eggs. As a rule the eggs of benthic nesting fishes are less numerous, larger, have a longer incubation period, and are at a more advanced developmental stage when hatched, compared to the eggs and larvae of pelagic spawning fishes. Incubation may last several days and the larvae then lead a pelagic existence for up to several weeks before settling on the bottom in a suitable reef habitat.
Data on reproductive modes is included in the databases.
Longevity, size
There is little information on the longevity of most eastern Pacific reef fishes. Perhaps one of the longest life spans is that of the Lemon Shark which may reach 50 years or more. Most of the larger reef sharks probably live at least to an age of 20-30 years. In general the larger reef fishes such as groupers and snappers tend to live longer than smaller species in the same family or genus. However, small snappers can live as long as much larger groupers. Otolith aging techniques indicate that large groupers may live at least 25 years and some snappers up to 30 years. Small species such as damselfishes and angelfishes may reach an age of 10 years or more.
A few data on longevity are included in the database. Whatever information is available from different sources, including our personal experience, is distilled to maximum known lengths in both the text and database. A limited amount of data is also presented on maximum known total weights.
Residents and vagrants
Almost 92% of the species treated here apparently seem to be sufficiently abundant and/or widespread to have resident populations in our region. Vagrants mainly (68%) include temperate species resident in the Californian and/or Peruvian provinces, while 19% of them are tropical Indo-Pacific species. The remaining vagrants include the few west Atlantic aliens introduced to our area (8%) either accidentally, through the Panama Canal, or deliberately, or are more widespread temperate species (5%).
Discover Life -- Shorefishes of the Tropical Eastern Pacific -- Biology
