Doc Talk 3/23/09 - Do Sport Fish Compete?
Doc Talk 3/16/09 - Good Old Days
Doc Talk 3/9/09 - Crappie Movement
Doc Talk 3/2/09 - Walleye Lake
Doc Talk 2/23/09 - Establishing Macrophytes
Doc Talk 2/16/09 - Turbid Waters
Doc Talk 2/9/09 - Stocking Salmon
Doc Talk 2/2/09 - Catching A Big Fish
Doc Talk 1/26/09 - Carrying Capacity
Doc Talk 1/19/09 - Seminole Bass
Doc Talk 1/12/09 - Flathead Catfish
Doc Talk 1/5/09 - Walleye Hatchery
Doc Talk 12/29/08 - Endocrine Disrupters
Do Sport Fish Compete? - 3/23/09 I hear it all the time: your sport fish ruined the fishing for my sport fish.
Stripers ruined the largemouth bass fishery in Lake Texoma and in Tennessee and Cumberland river impoundments. Smallmouth bass and walleye eat salmon smolts in the Columbia River. Muskie are eating the walleye, unless it’s a bass lake, in which case the muskie are eating the bass. Pennsylvania bass anglers are concerned about muskie stocking. The culprit is invariably a fish that was stocked.
The most studied controversy is striped bass and black bass interactions. Black bass anglers initially insisted that the stripers were eating black bass. But studies repeatedly showed that stripers eat primarily shad.
Then anglers insisted the stripers were eating all the shad and depriving bass of the abundant forage they needed for fast growth. Several studies have tested this theory, too.
The most rigorous study was done at Norris Reservoir, Tennessee by Steve Miranda at the Mississippi Cooperative Fish and Wildlife Research Unit. Norris is a predator-rich system that supports strong fisheries for largemouth bass, smallmouth bass, crappie, walleye and striped bass. All these fish share the shad-dominated forage base.
When the sampling and data analysis were complete, the average forage production exceeded what all the collective predators would consume. Competition only occurs when a resource by two or more species limits at least one of those species. Since food was not limiting, there was no competition for food and, therefore, no suppression of the black bass.
Of course, forage abundance fluctuates over time. When the researchers looked at the data on a year-by-year basis, they found that forage may be in short supply in three out of every five years. So yes, abundant stripers can compete with black bass for forage in some years.
“OK, so they do compete,” insists the black bass anglers. “Get rid of those stripers.”
If they quit stocking stripers, the total amount of all sport fish (black bass, crappie and walleye combined) would increase only one to four pounds per acre. So even when stripers compete with other game fish, the effect is very small.
So do sport fish compete? Sometimes, yes. But the competition is very limited unless the fish are unwisely stocked.
Are predaceous sport fish overstocked or stocked into systems where they can cause problems? Unfortunately, this sometimes happens. And when it does, it is invariably fueled by angler demands.
The bottom line is that the right fish in the right numbers means plenty of well-fed fast-growing fish, and diverse fishing opportunities. Good for the fish, good for fishing.
Good Old Days - 3/16/09 Did you ever hear a fishing story start, “Back in the good ol’days …”?
I hate to admit it, but I fished in the good old days. I often look back on many of those trips and smile, but I also enjoy a lot of good days in the present.
Bass in much of the southeastern United States are tough to catch compared to the northern fisheries I have the privilege to fish. Bass fishing pressure is high and pretty much year round in the south. This is in sharp contrast to the relatively low pressure in northern waters, not to mention the relatively short bass season.
I have often wondered about the affect of fishing pressure on bass populations, so I did some research. I assembled catch records for more than 250 large, national bass tournaments from 1980 until now by going through a hundred hours of data and gathering a bunch of statistical analyses.
After factoring in tournament format and a few other things that could bias the results, I found that angler catch rate, measured as bass weighed in per angler day, did not significantly change over the 30-year time frame.
Yes, there was a lot of variation among years, but neither the number of the fish nor the size of the fish had a significant upward or downward trend. These trends, or rather the lack of trends, were the same for different tournament formats and whether I used stats from the whole field of tournament anglers or just those that finished in the top 12 slots.
These results surprised me. If fishing pressure was a factor, you would expect catch (both numbers and size) to decline in this post-modern bass fishing world of increasing fishing pressure.
On the other hand, I would expect numbers of fish to increase as the knowledge and fishing efficiency of bass anglers increases and the tackle industry continues to supply new lures, new colors, and new techniques. I can run five miles in five minutes to an offshore weed bed or shell bar, pull right to the sweet spot marked on my GPS, and drop the trolling motor and fish in two foot waves. A far cry from my first boat, but it caught a lot of fish.
And since my data base was for tournament anglers, I would expect size of the fish to increase. According to hundreds of interviews I hear and read, these anglers are fishing for quality fish. In other words, catch rate may go down, but average size should go up.
Except for a brief bout with largemouth bass virus, I know of no documented cases of steady declines in bass populations.
The only conclusion I can make is that as bass anglers have evolved, so have the bass; anglers are better equipped to catch bass, bass are less catchable. This makes even more sense when you factor in catch and release. In the supposed good old days, a caught bass was a cooked bass. The populations were full of naïve bass.
Do I wish I could go back in time when bass were many and anglers were few? You bet, but I would want to fish with my modern tackle, boat, and gadgets.
The good ol’ days are now if you can keep pace with the bass.
And always remember, what’s good for the fish is good for fishing.
Crappie Movement - 3/9/09
Keeping Up With Summer Crappies Rob Hayward and his fishery students at the University of Missouri recently learned something about summertime crappie movement that may help you put more slabs in the boat.
They attached temperature-sensing transmitters to crappie in two small impoundments: Little Dixie Lake and Rocky Fork Lake. Both lakes stratify in the summer, and low oxygen below the thermocline restricts crappie to water in and above the thermocline.
A lot of standing timber surrounds Little Dixie Lake. The crappie occupied the warmest water available until the water reached 75 degrees. As the water steadily warmed they moved deeper. When the water reached 82 degrees the crappie stayed in the coolest water available. In other words, they were in the thermocline.
Unlike Little Dixie, steep-sided Rocky Fork Lake lacks standing timber. In the spring and early summer the crappie remained near the narrow fringe of shoreline vegetation. As the water warmed, Rocky Fork crappie moved deeper but they did not occupy the coolest water available until the lake hit 88 degrees.
That’s six degrees warmer than the temperature that sent Little Dixie crappie into the thermocline. Why the difference?
Well, that’s a question for another study, but here’s what Dr. Hayward came up with and it makes good sense to me. The crappie in Little Dixie could find their preferred temperature and stay associated with cover—the standing timber. The crappie simply moved vertically, staying close to the trees. The Rocky Fork crappie had to abandon the shoreline vegetation (the only cover available) to move to open water to find cooler water. While temperature affects crappie location, cover (or in this case, lack of cover) can modulate the effect of temperature.
It is also apparent from this study that temperature can dictate crappie location. As the water warms throughout the summer expect the crappie to move. Depending on the cover available, that movement may be vertical or it may be off shore and to deeper water. And always remember, what’s good for the fish is good for fishing.
Walleye Lake - 3/2/09
Good Walleye Real Estate Close your eyes. Let your mind travel to the best walleye lake you’ve ever fished. What do you see? A large lake? Clear water? Rocky shorelines flanked by birch and pine woodlands? Maybe rocky shoals?
If so, maybe you should have been a fisheries biologist because they have determined which lakes support good walleye populations.
Anglers expect walleye in every lake from New York to South Dakota, and millions of walleye are stocked every year to keep these anglers happy. But when the demand exceeds the supply, it’s time to prioritize.
To more effectively channel the limited fishery management resources, Michigan and Wisconsin fisheries researchers looked at the characteristics of lakes where walleye live and where they don’t. In short, they found that lakes that supported walleye, whether stocked or self-sustaining, were relatively large, relatively deep and had bottoms of sand and rock. Small, shallow, muck-bottomed lakes rarely supported good walleye populations.
The researchers dug deeper to see if they could determine differences between lakes with self-sustaining walleye populations (lakes with natural reproduction and good recruitment of walleye) and lakes that required stocking to maintain walleye populations.
They found that lakes with higher angler catch of muskie and smallmouth bass tended to have self-sustaining walleye populations. Lakes with higher angler catch rates of northern pike and largemouth bass required stocking to sustain walleye fisheries.
Putting it all together, physical characteristics of lakes were useful in determining whether the particular bodies of water would support walleye, and biological characteristics determined whether natural reproduction would sustain a walleye population.
Useful information for effective management? As they say in walleye country, you betcha. A northern state zip code, a few rocks and some birch trees doesn’t mean the lake will support a good walleye fishery, even if they are stocked. Yet every year thousands of walleye are stocked, sometimes in the wrong lakes, to satisfy popular demand. These fish could be better used in lakes that will support walleye. And now we can predict those lakes. Good management. Good for the fish, good for fishing.
Establishing Macrophytes - 2/23/09 There’s bass in the grass. And a whole bunch of other fish.
Rooted aquatic plants (what aquatic and fishery biologists call macrophytes) are good for our waters and good for fish. For starters, here are six reasons why: 1. Macrophyte root systems stabilize the bottom and reduce turbidity.
2. Macrophytes dampen waves to reduce shoreline erosion.
3. Macrophytes take up nutrients otherwise used by algae, and filter sediment to clear the water. The result is clearer water.
4. Macrophytes provide spawning habitat for some species and cover for the young of many fishes.
5. The plants provide abundant substrate for aquatic insects and other invertebrates that are important food for fishes.
6. And very importantly, macrophytes concentrate sport fish and improve fishing. Importantly, the plants concentrate fish in relatively shallow water where anglers are more efficient. At least once a year I travel to northern lakes to fish, and I’m usually fortunate to catch a lot. The pattern is simple: weedbeds.
But back home in southern rivers and reservoirs, macrophytes are often lacking. This is most unfortunate, because many of the reservoirs are aging and losing the woody cover that was once abundant when the reservoir was new.
For years agencies and anglers have been adding building fish attractors or adding brush piles. OK, but a lot of work, and the fruits of the labor have relatively short life spans.
A new solution is the intentional establishment of aquatic plants. We are on the bottom of the learning curve but have already seen successes.
We have learned that some plants are better pioneer species; they are relatively easy to establish and more tolerant of the harsh conditions present in the vegetation-free waters. Establishing pioneer species can make it easier to get other plants started and established.
We have learned that reservoirs are full of plant eaters and everything from terrestrial furbearers and whitetail deer to turtles. So we enclose the plantings with wire or plastic fencing to get the plants established. Soon they grow beyond the enclosures.
Aquatic ecologists have speculated that establishing native vegetation may suppress the establishment of non-native, problem plants like hydrilla and Eurasian water milfoil.
A big impediment to establishing macrophytes is a source of plants. Maybe it’s only wishful thinking, but I foresee the development of aquatic nurseries. Maybe some of our hatcheries could have greater net effect if we produced plants rather than fish. NAFC members understand the value of good habitat. If we had good habitat, less stocking would be necessary, and the stocked fish may have better survival and growth.
I am always in favor of management activities that improve habitat, but what I like about establishing macrophytes is that it provides a great opportunity for anglers to get involved. It’s the tedious work that is best accomplished by many hands and backs. Most of the successful macrophyte-establishment projects have been cooperative efforts with fishing clubs.
When the hard work is done, we have better habitat for a long time. It’s good for the fish, and definitely good for fishing.
Turbid Waters - 2/16/09
Dealing With Muddy Water With the exception of catfish, most of our North American sportfish are sight feeders. Or so we think when we spend $50 for three new custom-finish crankbaits or make sure the beads on our walleye spinner rigs are just the right color. Hey, we live in a visual world, fish must too.
Here’s what I know about fishing muddy water. Since fish can’t see much in muddy water, go find clear water so fish can see that spectacular new crankbait.
Unfortunately, I live and do a lot of my fishing in the south where water clarity can be highly variable. What to do when the clear water is gone?
I asked three bass pros, Timmy Horton, Ron Shaw, and Roger Stegall, to keep fishing logs to record the depth of water clarity (how far into the water they could see a white object like a spinnerbait or a jig) and the depth they caught their fish.
For each angler and for all anglers together, the depth at which they caught their fish was positively related to water clarity—the clearer the water, the deeper they caught their bass.
That probably doesn’t surprise you, but here is a number that you may find useful: All anglers caught at least three-fourths of their fish at depths less than eight times the depth you can see a spinnerbait.
So the next time you’re inescapably confronted with muddy water, restrict your fishing to eight times the depth you can see your lure.
What about the other 25 percent of the fish, or what do you do when the water is double-chocolate muddy?
The pros reminded me of what I’ve known all along as a biologist. But I guess I was too busy thinking like a human instead of a fish. Bass and other fish have the same senses we have. It just so happens that they not only see better than we do, they smell, taste and sense water movement better than we do. In particular, the lateral line system that detects water movement is more important to locating and capturing prey than previously thought.
What to do when the water turns really muddy? Fish shallow and use baits that move a lot of water. Use big bladed spinnerbaits for sure, but also big jigs, large soft plastic offerings and wide wobbling crankbaits.
Ignore the mud and think like a fish—a shallow fish.
And always remember, if it’s good for the fish, it’s good for fishing.
Stocking Salmon - 2/9/09 If I told you fishery biologists on the Pacific coast were stocking salmon carcasses, would you think I’ve been fishing in the hot sun too long? Historically, Pacific salmon stocks grew to adulthood in the ocean, and then ascended large rivers to reach their programmed spawning areas in tributary streams. The fish then die after spawning. It is a difficult life cycle to understand, but an overlooked aspect of this life cycle is the life after death. No, I don’t think salmon are reincarnated, but their carcasses provide food and nutrients to fuel the food web in these high-elevation, nutrient-poor systems. And it is this food web that provides the necessary nourishment for the salmon parr after they hatch. Migrations of the salmon stocks to these low-order tributaries have been blocked by dozens of dams, and as a result, the stocks decimated. That means less spawn, but it also means fewer nutrients, and fewer post-spawn salmon carcasses for hatching salmon and other fishes that reside in the rivers. The solution: stock salmon carcasses to replicate the historic conditions. After all, it is the natural food source for these streams. Obvious problems can occur with this “back-to-natural” idea. Getting the salmon carcasses would not be difficult, but storing them and distributing them into the streams would pose some significant logistical issues. In addition, there are also concerns of diseases. Some of these streams are already plagued by whirling disease, viral hemorrhagic septicemia, and other bacterial and viral diseases. Indiscriminant use of carcasses can introduce lethal diseases. Some scientists from various West Coast fisheries from Oregon to Alaska have been developing and testing “salmon carcass analogs.” In a nutshell, salmon carcasses, say from commercial processing plants, are ground, pasteurized to kill and deactivate pathogens, extruded into large pellets, and partially dried. The end-product is essentially a dead, spawned-out salmon. It offers the same suite of nutrients, right down to trace elements, as there would be in the real meal, and it’s disease free. It also has a good shelf life at room temperature, while dead salmon does not. And because the analog pellets have low moisture content, 100 pounds of pellets is the equivalent of 500 pounds of salmon. The shelf life and relatively low weight make it easy to provide the carcass analogs when needed. Preliminary evaluations of the effects on fish are encouraging. The analogs appear to bolster the aquatic food web, and condition, production, and lipid content of salmonids increased in the streams supplied with the analogs. This has a promising future both in terms of sustaining our natural anadromous salmon stocks, but also in relation to the resident fish in these streams. If it’s good for the fish, it’s good for fishing.
Catching A Big Fish - 2/2/09 Every angler I know—young old, rookie or veteran—wants to catch big fish. Doesn’t matter which species, a big fish is always exciting.
Let me tell you a fish story. Last December I was bass fishing at Bay Springs Lake in north Mississippi with my long-time fishing partner Ben Davis. We had caught a half-dozen keepers that morning. We pulled up on a point with a little brush on it about 9 a.m. and dropped the trolling motor. On Ben’s second cast he set the hook on a fish—a big fish. About 3 minutes later I had the privilege of netting a 12-10 largemouth. We did some high fiving, took some pictures and went back to fishing. The weather turned cold and rainy, but we fished the day out and caught more fish, including a couple more than five pounds.
I think we were both in some weird state of shock. Few words were spoken while we fished. I just kept wondering how rare is a fish of that magnitude, and what are the odds of catching such a rare fish. When I got home I went to work with some fishery calculations. I estimated that there might be one bass that big in about every 40 acres of Bay Springs Lake. But putting a lure on the fish’s head doesn’t mean they’ll bite, and if they do you still have to land the behemoth.
So I looked at professional bass tournament records from 2002-06. I excluded tournaments on lakes not expected to yield double-digit bass. What I found was that 64,500 angler days in these tournaments brought five bass bigger than 12 pounds to the scales. That’s one bass over 12 pounds per almost 13,000 angler days. And that’s 13,000 days by the best anglers fishing the best bass lakes at the best times.
So how special was Ben’s bass? Let me put it this way: If you are an avid angler who fishes 50 days a year and live to be very old, it would take more than four lifetimes to catch a largemouth over 12.
Keep fishing. The next cast could catch the biggest fish or your lifetime. Or several lifetimes. And always remember, what’s good for the fish is good for fishing.
Carrying Capacity - 1/26/09
Simple And Fundamental Concepts Drive Fishery Management
I’ve been involved with fishery management as a researcher, teacher, and manager for more than 30 years. Despite the advances in knowledge since my grad school days, I am repeatedly reminded that some basic ecological principles govern fish populations. Successful management capitalizes on those principles.
At the top of that list is the concept of carrying capacity. Carrying capacity is the amount, usually measured as weight, of animals that a habitat can support on a sustained basis.
When a population is below carrying capacity, it will grow—either in numbers of individuals, in size of individual fish, or both—to reach carrying capacity. If the weight--what fishery biologists call biomass—is above carrying capacity, growth slows and mortality reduces the population.
Now think about regulations. When populations are severely reduced by angling, we use minimum length limits and reduced creel limits to conserve fish. This allows the population to increase. Increase to what? To carrying capacity. When a population is at carrying capacity and growth of fish is slow, we use liberal length limits or high creel limits to reduce the population so the remaining individuals can grow to larger size.
Every angler, and biologist, dreams of lakes and streams full of large, fast-growing fish. Not possible—when the fish are numerous, growth will be slow and there won’t be many large fish. Carrying capacity.
Conversely, if a lake has large fish, it won’t have many fish. Carrying capacity.
Carrying capacity doesn’t change in a certain lake or stream, but it varies among different waters. Waters with fertile watersheds produce more plants, which in turn produce more invertebrates and more fish. Anglers should not expect to catch as many or as large fish from low fertility waters as highly productive eutrophic waters.
Understanding basic ecological principles goes a long way to producing good fishing and to adjusting your expectations as and angler. And understanding carrying capacity means good management. Good management. Good for the fish, good for fishing.
Seminole Bass - 1/19/09
At least several dozen studies involving radio tracking largemouth bass all say pretty much the same thing—bass occupy a home area. The home areas range from several to more than 20 acres. Now, frankly, that doesn’t tell me much—20 acres is a pretty big piece of water to seine with a crankbait.
With a recent largemouth radio tracking on Lake Seminole, a Chattahoochee River impoundment on the Florida-Georgia line by Auburn University, scientists caught my attention for a couple reasons.
First, the scientists tracked three-plus pound fish. Got your attention?
Second, they tracked the same fish throughout a year. Now we can compare the seasonal whereabouts of individual fish.
High-use areas ranged from a low of seven acres in winter to a high of 13 acres in the summer. Fish were most mobile in the fall and most sedentary in spring and summer. Bass moved least during daytime hours, and had higher and similar movement rates during dawn, dusk and night. But that’s not really news, and it doesn’t help me find bass.
What I found interesting is that most of the bass—each individual--occupied a shallow-water area and a deep-water area. Bass were most likely to be found in deep water in the fall and least likely to be found in shallow water in the winter. Nevertheless, some bass were shallow in all seasons.
The bimodal, deep-shallow depth distribution was also apparent across all daily time periods, but the bass were more likely to be in deep water during dawn and daytime, and more likely to be shallow at dusk and at night.
How fish behave always has a habitat component to it. Seminole is loaded with deep- and shallow-water vegetation. Whether deep or shallow, the fish were always with cover. So don’t count on the onshore—offshore Seminole shuffle to occur in lakes lacking deep cover or in lakes with good deep cover but lacking shoreline cover.
How predators behave is always related to their forage. It may also be important that sunfish are abundant and a big part of the bass’ diet. Sunfish dwell in the deep and shallow vegetation that abounds in Seminole. I would expect similar behavior anywhere bass are dining on weed-seeking prey, but all bets are off in a lake or reservoir where shad are the dominant forage.
Know your quary, but also know their forage. Fish the best habitat, and catch a lot of fish.
And remember, what’s good for the fish is good for fishing.
Flathead Catfish - 1/12/09
Don’t Take Him Away From Home If you take your catfishin’ seriously and you live between the Appalachians and the Rockies, flathead catfish probably have a special place in your psyche.
Now the flathead isn’t going to win any beauty contests but it’s a top contender in the strongest fish arena. It’s a fish-eating machine. And it’s a fine eating fish.
While the fish is popular among anglers and biologists in its native middle-U.S. range, it’s about as popular as the snakehead outside its range.
The fish has now been introduced into rivers from the Apalachicola in Florida up the eastern seaboard to the Susquehanna in Pennsylvania. In coastal rivers from Georgia to Virginia the story is the same—flatheads decimate the native redbreast sunfish, bullheads, white catfish and even channel cats.
Although some eastern anglers have found the flathead a desirable sport and food fish, most disdain it for destroying the fisheries that they are accustomed to enjoying.
Like other non-native aquatic species, eliminating the invading flatheads is not possible. Nevertheless, some efforts are in place to reduce them. Georgia DNR has hired a fishery biologist and a couple technicians to reduce the population in the Satilla River. While the team searches for long-term solutions, like genetics to reduce reproduction, they are removing the fish by electrofishing. In the first four months of this program they removed more than 4,000 fish—24,000 pounds.
This Jekyll and Hyde fish has the biologists stumped—why does it cause problems outside its native range? I don’t claim to have the answer, but reading all the studies suggests to me that the flathead in Eastern rivers is just like a flathead in Midwestern rivers—it hunkers down in sheltered areas until chow time, then moves into slow-flowing areas to feed. That’s where the redbreast sunfish and bullheads live. Unfortunately, the redbreast and some of the flathead’s cousins in the catfish clan have evolved without sharing their space with this predator and possibly lack an escape response.
How did the flatheads arrive? Probably anglers. I’ll confess that a side of me gets excited about another large sport fish to catch, but introducing fish is at best selfish and usually disastrous.
There is a lesson here—a fish doesn’t have to come from a foreign land to be a nuisance aquatic species. Let’s not jeopardize our diverse and quality fisheries to make them all the same.
The right fish for any water is the one that already lives there.
No introductions—good for the fish that live there, good for fishing.
Walleye Hatchery - 1/5/09
New Tricks For Producing Walleyes For Stocking Millions of walleye are stocked every year. When stocked in the right lakes—lakes that are relatively large, moderately deep and clear, with a lot of sand and gravel bottom—stocking can be an effective way to sustain or supplement walleye populations.
Survival of stocked walleye often can be improved by stocking larger fish. Unfortunately, there is no way a state fisheries agency can provide millions of larger fish—what we call advanced fingerlings. The reason is simple—rearing fry to 6 to 8 inches requires a lot of hatchery ponds and a lot of minnows.
There two solutions: extensive culture and intensive culture.
Extensive walleye culture, as practiced in Minnesota and other states, involves stocking fry into off-hatchery ponds or wetlands that lack predaceous fish. The ponds may be fertilized and sometimes forage fish are stocked. The young walleye are collected in the fall by seining or trap netting, and then transported to designated public waters.
Extensive culture is relatively inexpensive, costing little more than personnel time and vehicle fuel. But the harvest is relatively inefficient and the fish have to endure a lot of handling.
Intensive culture is hardly new, but the intensive culture of walleye in state hatcheries is a new development. The Iowa DNR has been a leader in walleye intensive culture and pioneering new tricks every year.
Intensive culture involves training the fry to eat prepared hatchery food. Walleye are predators, and training walleye to eat fish pellets is rather exacting. The fry are concentrated at very high densities in hatchery tanks and fed a highly palatable and high-protein diet. Automatic feeders dispense feed every few minutes so the little walleye are literally swimming in food.
Feed training is complete in a couple weeks and the walleye are weaned from the gourmet starter diet to a less expensive hatchery diet. They are fed in raceways and tanks throughout the summer. In the fall, the fish are easily harvested, and 6 to 8 inch advanced fingerlings are shipped to designated public waters.
There are two ways to build a walleye. The best method depends on the resources available. When stocked wisely, these fish can help get walleye fisheries back on track.
The right numbers of the right size walleye means abundant, fast-growing fish. Good for the fish, good for fishing.
Endocrine Disrupters - 12/29/08
What You Can’t See Can Hurt You (And Fish) Many of you have heard of endocrine disrupters; but in case you haven’t, these are chemicals introduced into the environment that mimic hormones or otherwise affect the endocrine system. The endocrine system produces hormones that are essential to normal growth, development, behavior and reproduction. So when you mess with the endocrine system, a lot of bad stuff can happen.
The effects on fish? So far, the known effects are mostly related to reproduction: intersex fish—for example, males with eggs in the testes--and skewed sex ratios. However, the endocrine system can also affect development, growth and disease resistance. And we do know that endocrine disrupters can adversely affect the food web that supports the fish.
Endocrine disrupters are not new, but our knowledge of them and their effects is fairly recent and increasing daily. Indeed, endocrine disruption is a relatively new and widely used tool for detecting the presence of many toxic substances that formerly were not known to be problems or were present in the environment in concentrations below what could be detected by conventional analytical procedures.
Many endocrine disrupters have been in our environment for a long time—organochlorines like DDT and PCBs. Although long since banned, they persist in the environment.
And there are new endocrine disrupters discovered daily. Some are effluents from paper mills and other industries, mercury in the coal burned to produce electricity, and agricultural chemicals. Confined animal feed operations use hormones to manipulate growth and reproduction and antibiotics to control disease. These chemicals are excreted and find their way into both surface and ground waters.
People are a major source of endocrine disrupters. Our paradoxically health-conscious but chemically dependent society consumes more than 10,000 pharmaceutical and personal care products (PCPPs) from birth control pills to musk fragrances. These chemicals pass through our bodies, then through our wastewater treatment facilities, and into our surface waters. Even advanced wastewater treatment facilities do not alter the endocrine disrupters.
The scary facts are that regulatory agencies are allowing these chemicals into the environment. And even when we stop additions, many of these chemicals can be fairly long lived. And then there are a long list of chemicals whose fate is not known. Are There Solutions? Possibly technology along the lines of bioremediation—microorganisms capable of breaking down these ED chemicals--may reduce the burden.
Certainly, pay attention to the news and tell your elected officials that American needs to stop discharging endocrine disrupters into the environment. Be an active supporter of efforts to reduce and eliminate the introduction of these substances.
But don’t just blame industry and agriculture. If you are a typical American, you are part of the problem too. Minimize your use of PCPPs. And don’t flush unused PCPPs. Take advantage of programs that collect your unused PCPP. If there are no such programs in your area encourage civic leaders to start one.
This is a serious situation for fish and other aquatic organisms, and it directly affects your personal health. I think we are just seeing the proverbial tip of the iceberg. It’s good for the fish, and it’s good for fishing.
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