In my last post, I mentioned crayfish and eels, and my observations of the relationships between the creatures in the creek. To elaborate, we have to go back to November of 2004, and the Athos I oil spill in the Delaware River near Paulsboro.
The actual spill was relatively small, less than 100,000 gallons, and pretty far downstream from us, it was startling to see how far the effects reached. Since the Delaware River is tidal, the oil that escaped from the containment booms came upriver with the tides, and was dragged behind boats that went through it. Although the Coast Guard told me that the oil stopped at the Tacony Palmyra Bridge (? interesting, since the water movement doesn't stop there), my students and I observed oil on the riverbank all the way up at Taylor's farm. Remembering the horror of the Exxon Valdez, I wondered what kind of damage would be seen in our river and its tributaries.
When crude oil hits the cold water, it turns into a heavy, dense tar-like goo that sinks to the bottom. Bottom feeders, like crayfish, and any creatures that hibernate under the mud, have to get through the goo when they come out of hibernation, or try to find food.
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As it turns out, petroleum products affect the reproductive processes of crustaceans. So even though there was no massive die-off that fall or spring, I noted that the crayfish I observed didn't look quite right, and there were very few pregnant specimens. Crayfish carry their eggs externally - the few egg bearers I did see had very few eggs, and the eggs were very loosely attached and fell off easily.
Spring of 2006 is when things began to fall apart. Hardly any baby crayfish had survived from the previous year, and very few adults could be found anywhere; the few seen disappeared by early summer. So what, you may say? It seems that crayfish eat little baby eels. With no predators, the eel population exploded. If I tried to get a net full of minnows, I got a net full of eels, big eels. The eels proceeded to eat everything they could, and the minnow population dwindled. With the minnows, and then the small sunnies and bass gone, the big fish had no reason to hang around. Once the bass, carp and catfish left, the large birds left. No egrets, no herons, no hawks, and worst of all, the eagles moved away. It was the quietest summer we've ever had along the creek. You take the bird sounds for granted until they're gone.
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Finally, in the spring of 2010, I noticed that the crayfish population had grown, the minnows were back, the eels were back in there proper numbers, and the creek seemed to be back. I was positive when the catfish returned, with the rest of the higher ranking members of the food chain right behind them.
While thrilled that the Pompeston had recovered, I was devasted by the disaster in the Gulf of Mexico last year. Experts argue back and forth about the health of the gulf and its inhabitants, but if you think about the 6 years it took for the Pompeston to come back, how long will it take the Gulf to be restored?
