Aboard the R/V Pacific Storm, San Carlos, Baja California Sur, Mexico. How could the presence of squid at the same spot vary so widely from one day to the next with no apparent difference in wind or weather? During this second night there were dolphins present at every spot we fished (audible by their breathing even in the dark), whereas we noticed none the night before. Had the excitement of seeing squid dulled our sense of hearing the first night? Maybe, but the local fishermen (who know a LOT of squid biology – that’s why we work with them) say that dolphins scare the squid away. I personally favor this idea.
Since marine mammals are their main predators here, it would seem to be a healthy choice for squid to depart an area invaded by mammalian predators hunting by sonar at night. Although the dolphin species present probably couldn’t even eat a squid of the size we were catching (they need to swallow them whole), perhaps it takes a night of fruitless fishing (squidless sonaring?) for them to realize that. Perhaps the dolphins moved on, and the next night was full of squid again. But we never found out – we had to return late that night to San Carlos to meet airline schedules for personnel changes on Saturday. I guess it’s time to call our commercial fishing contacts in Santa Rosalia and get the update – again, you can learn a lot from local knowledge.
I have never seen squid abundance swing so wildly from boom to bust in one day like this. Spring is a time of change in the Gulf. We know that the most squid migrate from Sonora to Baja in the spring, and maybe the vanguard of the migration (which may be what we encountered in Santa Rosalia) is especially sensitive to environmental influences -- such as temperature changes, windy periods or dolphin attacks -- that are not so influential once the population establishes itself in the local ecosystem.
Clearly, studying such perturbations, which are really natural experiments, could teach us a lot. You just need to identify the experimental variable. But it’s not like physics – you can’t push a button and predict the result. Right now we are still trying to build up a picture of the ecosystem and environment in times of squid stability in Santa Rosalia, generally from June through October. We originally hoped that this trip in March would have provided a complementary picture of when squid were absent – but the squid season in Santa Rosalia appears to have started unusually early.