Why are more lobsters dying in tidal pounds? Why is mortality increasing? Harrington fisherman, poundkeeper and Maine Lobster Pound Association (MLPA) President Bruce Portrie reported shrinkage rates in his pound and others “increased over the last three pounding seasons.” (The industry prefers the euphemism “shrinkage” to “death” or “mortality.”)
In other words, each year for last three, more lobsters put in tidal pounds died than the year before. (Poundkeepers ascertain shrinkage rates after draining their pounds at the end of each pounding season.)
These increasing rates came as a blow to Portrie who used to take pride in his low shrinkage rates. Asked the reason for the yearly increase in dead lobster, Portrie said, “If I knew that, I’d be in good shape. I really don’t. All I can do is speculate. I have not done anything different in my process from fall to spring. Everything has been done pretty much the same since the first year I put lobsters in and had a 2.1 percent [shrinkage rate].”
For years, he has pounded (put in his pound) only lobster with good firm shells, as opposed to soft-shelled shedders, and he feeds his lobster “cod racks” (essentially the bones or what remains after removing the edible parts of cod).
Puzzled and concerned, Portrie and other poundkeepers enlisted the help of the Lobster Institute and the University of Maine’s Aquatic Animal Health Laboratory (AAHL).
Enter University of Maine Master’s degree candidate David Basti, a former veterinarian who decided to leave that career after suffering burnout from long hours, emergency work and the demands of a large practice. He now works with ten-legged arthopods instead of the usual four-legged mammals and loves it despite knowing that his love of animals only goes so far with the naturally aggressive Homarus americanus.
Because Basti got his bachelor’s degree in marine biology, he’s not exactly a novice. He credits Robert Bayer, Ph.D., of the Lobster Institute, with helping him get into graduate school, saying that he’d been out of school so long, he’d had his doubts about starting again. He said of Bayer, “Bob’s longstanding good relationship with the lobster industry is allowing us to work with people like Bruce [Portrie] who are willing to provide us with lobster for our work. The people in the MLPA have been giving us a lot of help,” he said, “money, too. But the main thing is they’re giving us lobster, so we can do research on them, and they’re taking us out on boats to do research.” In other words, this lobster research is a collaborative effort by poundkeepers, the Lobster Institute, and the researchers at the Maine Aquatic Animal Health Laboratory.
Bayer considers having a veterinarian on the team a windfall and said, “Dave is a huge asset with his animal health training. We are so lucky to have him.”
“What veterinarians offer is a strong animal-medical background,” agreed microbiologist and virologist Deborah Bouchard, Manager of the laboratory. She added, “More and more veterinarians are getting interested in the aquaculture field, which is looking at the production of animals for a food source.” Basti, Bouchard and the other researchers are trying to determine whether a lobster is healthy or diseased, but beyond that, Basti reported that the DMR recently awarded the Maine Aquatic Animal Health Laboratory a grant of over $50,000 “to study possible stressors along the supply chain of lobsters.” He and Bouchard are the researchers and Professor of Marine Science and Aquaculture Ian Bricknell is the consultant on the project.
“Everybody says nothing has changed in handling practices,” Basti said. “We’re trying to find what might be happening or changing in how lobster are handled and moved from the trap to the final destination: the pound or overseas. We have to find the point at which they cannot recover. What stress may or might contribute to their mortality or might predispose them to [mortality.]”
Basti finds a major stressor the lobster’s inability to breathe air. It may live four days in air if kept cool and wet, but from the time it leaves salt water it is asphyxiating, and that causes stress, right there. He said, “We’re looking at the effects of long-term exposure to air at higher temperatures.” He also mentioned dramatic changes in water temperatures and said, “We’re trying to reproduce in the lab the stresses that lobster might encounter between the trap and the final destination.”
For the most part, the researchers are looking at the pound as that destination. “Something happens between the trap and the pound that might predispose the lobster to mortality,” Basti said and went on to note that the lab’s mathematical model shows that newly molted lobster is at the highest risk.
“It may not necessarily be depth or the vigor of the animal,” he said. The biggest predictor of mortality apparently turns out to be shell stage, or how recently the lobster molted, according to the lab’s model, which is based on pound stocking experiments. Basti said, “This is something we are looking at.” In Lobsterese, it’s either those jellies, the unbandable lobsters that must be held with both hands, or those with paper-bag-thin shells that are most likely to die.
As he spoke, Basti kept saying, “It’s not rocket science.” He said, “People are looking for very complicated causes when it may be something simple we can do.”
By a process of elimination, the researchers have ruled out disease as a cause of shrinkage. “The state of the lobster is healthy,” he said. “There is no evidence of a disease including red tail and shell disease at this time. These lobsters are beautiful.”
Portrie said, “I attribute the shrink to the handling of the lobsters by the fishermen. And I’m a fisherman. I’ve been a fisherman for years. I’ve been on people’s boats and I know how people handle lobsters. Once they get them in the traps and get them on the boat, they don’t care about them just as long as they can get them back to the dock and get paid. I see them standing on the boat throwing lobsters from one side of the boat to the live barrel, crate, or whatever.”
Basti agrees and said he thinks pound shrinkage may indeed result from the stress of transport and rough handling of newly molted lobster. “The work I just spent a year or two doing shows it’s likely physiological stress in newly molted lobster. What if we could have a separate container for lobster with really soft shells? There’s a degree of difference between lobster that molted a week ago and those with harder shells. You can tell the difference.”
He went on, “Lobsters don’t breathe out of water. They’re slowly suffocating, and that’s a lot of stress. They can compensate; they’re very complex, but there’s a breaking point beyond which they cannot recover, and that what I’m looking for.
“Almost all mortalities occur within two weeks of the lobster going in the pound. Seven-to-14 days is when you’ll find most. I think they haven’t survived the movement or are unable to recover from being taken from the water and being in air.”
“Why not pack them in seaweed and keep them cold?” He continued, “Some come in crates packed on top of each other. Those lobster had been packed in seaweed and kept cold were beautiful. Those packed on top of each other in a crate and allowed to get warm and dry and stressed from contact with each other …. It’s not rocket science.”
He suggested treating the lobster, as he put it, “a little more gingerly,” that careful handling is “very important,” and said of the work done by Bouchard and others in the lab, “We’ve got some real strong marine science: we think stress is the biggest factor in mortality in pounds.” He added, “Long exposure to air at warm temperature is a big problem.” Finally, he said, “There are a lot of lobster people who are very concerned and willing to listen.”