Thursday, 27 September 2012

Identification of Demersal and Pelagic Eggs

Oviparous fishes classified into demersal spawners and pelagic spawners, the eggs they extrude are either demersal (on the bottom) or pelagic (above the bottom, and often at or near the surface). Common characteristic of eggs are tabled below.

Characteristic                                    Demersal                    Pelagic
Usual Size                                           > 1 mm                        ≤ 1 mm
Specific Gravity                                  greater                          less
Envelope                                            thicker                          thinner
Color                                                 opaque, colored             transparent
Amt. of Yolk                                       large                            small
Period of Dev. (Temperate)                  longer                           short
Parental Care                                      common                       none
Fecundity                                           low                              great (>1 million)
Larvae                                               swim/feed @ once         float/yolk sac
Dispersal                                            probably low                 probably high

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