I was recently given a rare opportunity to see the diversity of fishes caught on last summer’s Bering Sea trawl survey. I had an unwieldy bag of frozen fish that it took me a while to sort through and two days to thaw out. I hauled two totes of these fish to Kodiak Middle School for an after-school dissection, which I wasn’t sure would be attended all that well.
Setting out the goodies, there were cod with barbels on their chin and torpedo shaped black cod and sablefish, and flat halibut and a sole. There were several rockfish of various species with their impressive dorsal spines, some of them black, but also a red banded, and sculpins big and small. There were small feeder fish like the shiny, long sandlance and eulachon, and the deepwater lamp fish, which have photophores they can activate like little lights along their sides. There were some eel-like long sandfish, which I had never seen before and there were even some popeye grenadiers, citizens of the dark deep-sea floor. There was also a warbonnet and several surgeon poachers, which are fish so different looking one can’t help admire the diversity of life. I dissected a prow fish with a blunt snout and pores all over its face, which are sensory organs. The little label the biologist had included with this specimen read “eats jellyfish”, but an inspection of its stomach content only revealed an indistinguishable slime.
Among the most impressive specimen in the collection were several large sculpins, called Irish Lords. As one of my friends was there with her son, she took a video of me explaining the external features of the fish. The belly of the fish was huge as if it had swallowed a volleyball. Somebody said that it must have come up from depth too fast. A good guess, but I knew that was not what made this fish look so out of proportion. Let me explain: Some fish have a swim bladder, an organ which helps them control their buoyancy. Like a diver with an inflatable scuba vest, the fish can add air into the swim bladder when it goes deeper and releases air out of it when it moves toward the surface. The volume of the gas in the swim bladder (or dive vest) expands as the depth, and with it the pressure of the water acting on the gas, decreases. If fish or diver do not release gas while ascending to the surface, the volume expands, possibly to more than the swim bladder can hold. In rock fish, this can cause the fish to surface with its swim bladder popping out of its mouth.
The red Irish Lord was not full of air. I made a small slit in its abdominal cavity and out came a surprise! There were millions of eggs, but what was really amazing was the color of those eggs: They were bright turquoise blue!
In ecology, an organism that produces a lot of eggs like our red Irish Lord (or should I say “lady”), and releases them into the water without guarding or protecting them from predation is called an r-strategist. The “r” stands for reproduction. On the other side of the spectrum is the K-strategist. The “K” stands for Kapazitaet, which is the German word for capacity, and refers in this context to the carrying capacity of the habitat. The idea is that when there is a lot of competition, the better trained an offspring is the more chance of survival they have. The prime example for this strategy are orca whales. Not only do the young stay with their family for many years, and in the case of females forever, even the grandmothers in the pod take a prime role in teaching the young to hunt. Thus, there is a huge energy investment in the offspring and there are only very few calves born. The whales also communicate with each other, which means that they must have some sort of individual identifier for each member of the pod, you might call it a name.
Obviously, the Irish Lord, with its millions of larvae, will not give them names. In most human cultures, if there is high infant mortality the naming of infants and the ritual to accept them into society is postponed until the likelihood of survival is high. By that same human reasoning, it would make sense for the Irish Lord to ignore her larvae, as their likelihood of survival is extremely small. If we assume that six of all those eggs survive to maturity, which is already a generous guess and we assume one million eggs in that big belly, then we would have a survival rate of 6/1 million, which is 0.000006, definitely too low to name the blue egg.
But first, those eggs have to be fertilized. Unlike in humans and other organisms with internal fertilization, in most fishes the egg is not fertilized until after it is laid, and unless it is fertilized its chance of hatching is zero. According to Wikipedia, Irish Lords do guard the nest where the eggs are laid. Usually this job falls to the female, but there seem to be cases where the males build and guard the nest.
I can’t help but wonder: are those larvae that hatch from the blue eggs also blue? Are there little smurf fish drifting in the depths of the Bering Sea? The ocean has so many amazing surprises and wonders. By the way, if you have a child in Middle school: There will be a crab and crayfish dissection in room 102 on Dec. 6 at 2:45 p.m., a squid and clam dissection on Dec. 13 same time and place, and a sea star dissection on Dec. 20. These are free for migrant education program participants, and come at a small cost for all others. Please contact the front desk for more info.