Thunder and lightning ratcheted on the horizon last evening – and then rain broke loose in torrents, flooding the air with drops so large and thick that the trees along the creek bank vanished behind a silver curtain. As hard as it poured down, it didn’t rain very long and then the clouds lowered away to the east and a rainbow ignited with sunset’s fire.
At water’s edge, wind-driven shoals of dead fish washed into shoreline banks of reeds. A few flipped weakly further out, clearly in their fading moments. “Bunker,” I thought, “what killed them?” Just yesterday menhaden trawlers directed by a spotter plane dragged the deeper waters off the sandbars along the Chesapeake. Hardly sporting, but then it’s not that kind of fishery. Maybe these bunker were casualties of clumsy seining and rent nets. Or, maybe the storm killed them.
I write to my friend P.G. at the Virginia Institute of Marine Science in the seaside village of Wachapeague (also home to the famous Cake Wheel – but that’s another topic altogether), reporting, “Following the storm tonight, I went down to look out over the creek and discovered a significant fish kill. I have no idea what would have happened, but they weren’t there before the storms. They looked like bunker, but I’m not sure. The storm here didn’t last long, but it rained so hard you couldn’t see the creek from the kitchen window. No lightning strikes.“
P.G. replied, “If it was indeed bunker then it was likely a temporary dissolved oxygen issue. The scenario you describe is actually fairly common this time of year, although it happens in different creeks from year to year. As you know bunker are schooling fish and will often enter small creeks in high numbers. Sometimes they can consume all the oxygen before the school can re-orient and hit open water. However, this seems more prevalent during/just after storms. A small creek like Westerhouse can actual ‘turn over’ like a pond when a deluge of colder rainwater is introduced. These waters will create a boundary that doesn’t mix for awhile which cuts off the bottom half from being oxygenated at the surface. A school will quickly deplete the available oxygen. You will still likely see dead fish, but let me know if you see numbers of sick but alive fish. You may see some lethargic near the surface trying to ‘gulp’ air…again indicative of ongoing dissolved oxygen issue.” This is one of the traits I most admire in P.G., an ability to cut to the chase on the topic of dead fish, explain things clearly, and remain accessible.
P.G.’s note set me to thinking. I replied with more observations and questions, “The kill was quick and I’ve seen not seen any more dead fish this morning. Will this kill the other animals in the creek: crabs, shellfish, silversides, etc.? Do you want me to save and freeze a couple of the dead fish for the lab?” P.G. diplomatically declined the offer of dead fish (and by now the crabs and other scavengers had been after the bobbing buffet): “Typically the other living resources are not damaged. The dissolved oxygen issue is usually quite temporary…long enough to kill the fish with high metabolism, but short enough that any benthic critter including bivalves hardly notice it. The low dissolved oxygen ‘cloud’ is often highly associated with the water in and adjacent to the fish school. Smaller fish seem to be able to move to areas a short distance away and ‘chill out.’ Crabs can sometimes get caught in the mix…they are quite sensitive to low dissolved oygen, but again only those basically in the vicinity of the fish. I also think menhaden behavior probably plays into it as well as they seem to act quite agitated and probably increase their oxygen demand right at the time it would be well served to limit it by inactivity. Nature of that species, I believe.”
I’ve seen these fish in action on late afternoons when high tide deepens the water around the dock. They flash and flip, bolts of bright and animate light pursuing plankton. Bunker with their wide mouths are voracious. I suspect they chase smaller fish, but P.G. gently corrects me, “Looks like bunker…if you look into that large mouth you should be able to see combs on the gill arches…even though the gaps look big, as a unit they do effectively filter out the large zooplankton and the large mouth funnels loads of water through. Also, there will be an absence of teeth.” Driven and blinded by gluttony, the bunker (apparently thinking very small thoughts) let this stormy evening lead to the occasion of their own undoing. The unrestrained pursuit of appetite exists as its own kind of damning pride. Now, I don’t think of these fish as sinful in the sense of spiritual failure. It is conceivable that the only remorse a bunker might entertain is that it had eaten all the plankton and no more were to be had – but I doubt it. A bunker’s gluttony it seems is of the unthinking variety. They school into the creeks, ravage their micro-snack-size brethren, and move on. And, then this evening it rains in rivers, the creek layered salt-water oxygen-rich and rain-water oxygen-bereft inverts. In frantic flight bunker burn through the remaining oxygen and, en masse, drown. It’s too late, the tide rains bunker from the bottom up. “The wages of sin,” I’ve heard, “is death.” Looks as if the dead bunker are a case in point.
Wondering what to do with the bounty of dead bunker on my doorstep, I discern black clouds in the gentle arc of the horizon and hear thunder foreshadowing rain. Could be another bad day for bunker – but an instructive one for folks inclined to parables on sin and salvation.