Browsing Tag: yellow tang surgeonfish

    The secret lives of baby fish – Amy McDermott
    Articles, Blog

    The secret lives of baby fish – Amy McDermott

    October 9, 2019


    What you’re looking at
    isn’t some weird x-ray. It’s actually a baby yellow tang surgeonfish
    at two months old. And you thought your childhood
    was awkward. But here is the same fish as an adult, a beautiful inhabitant of the
    Indian and Pacific Oceans’ coral reefs and one of the most popular captive fish
    for salt water aquariums. Of the 27,000 known fish species,
    over a quarter live on coral reefs that make up less than 1%
    of the Earth’s surface. But prior to settling down in this
    diverse tropical environment, baby coral reef fish face the difficult
    process of growing up on their own, undergoing drastic changes,
    and the journey of a lifetime before they find that reef to call home. The life cycle for most of these fish begins when their parents spew
    sperm and eggs into the water column. This can happen daily, seasonally,
    or yearly depending on the species, generally following lunar or
    seasonal tidal patterns. Left to their fate, the fertilized eggs
    drift with the currents, and millions of baby larvae
    hatch into the world. When they first emerge,
    the larvae are tiny and vulnerable. Some don’t even have gills yet
    and must absorb oxygen directly from the water
    through their tissue-thin skin. They may float in the water column
    anywhere from minutes to months, sometimes drifting thousands of miles
    across vast oceans, far from the reefs where they were born. Along the way, they must
    successfully avoid predators, obtain food, and ride the right currents
    to find their way to a suitable adult habitat, which might as well be a needle
    in vast haystack of ocean. So, how did they accomplish this feat? Until recently, marine biologists thought of
    larval fish as largely passive drifters, dispersed by ocean currents
    to distant locales. But in the last 20 years,
    new research has suggested that larvae may not be
    as helpless as they seem, and are capable of taking
    their fate in their own fins to maximize their chances of survival. The larvae of many species are
    unexpectedly strong swimmers, and can move vertically in the water column
    to place themselves in different water masses and preferentially ride certain currents. These fish may be choosing the best routes
    to their eventual homes. When searching for these homes, evidence suggests that larvae navigate
    via a complex suite of sensory systems, detecting both sound and smell. Odor, in particular, allows larvae to
    distinguish between different environments, even adjacent reefs, helping guide them toward their
    preferred adult habitats. Many will head for far-flung locales
    miles away from their birth place. But some will use smell
    and other sensory cues to navigate back to the reefs
    where they were born, even if they remain in the
    larval stage for months. So, what happens when larvae
    do find a suitable coral reef? Do they risk it all in one jump
    from the water column, hoping to land in exactly
    the right spot to settle down and metamorphose into adults? Not exactly. Instead, larvae appear to have
    more of a bungee system. Larvae will drop down in the water column
    to check out a reef below. If conditions aren’t right,
    they can jump back up into higher water masses and ride on, chancing that the next reef
    they find will be a better fit. But this is the point
    where our knowledge ends. We don’t know the geographic movements
    of individual larva for most species. Nor do we know which exact environmental
    cues and behaviors they use to navigate to the reefs
    they will call home. But we do know that these tiny trekkers are more than the fragile
    and helpless creatures science once believed them to be. The secret lives of baby fish
    remain largely mysterious to us, unknown adventures waiting to be told.