Showing posts with label fish. Show all posts
Showing posts with label fish. Show all posts

Monday, October 5, 2009

A river may once again run through it...

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This past week has been a remarkable, mixed, week for the environment in the San Joaquin valley! First the good news: water began to flow through the San Joaquin river's heavily impacted (dammed / modified / channeled / dredged / damaged) course as part of a major restoration effort decades in the making, when federal authorities released water from Friant Dam, just above Fresno. The Fresno Bee has been covering the story really well these past few days, with a special feature, and you can jump into the stream with this report from Friday:




FRESNO, Calif. -- When Darrell Imperatrice was a boy, California's San Joaquin River teemed with so many king salmon his father could catch 40-pound fish using only a pitchfork.


Then the salmon vanished from the icy river for nearly 60 years, after a colossal federal dam built to nurture the croplands below dried up their habitat.


Now, as federal officials try to bring the fish back through a sweeping restoration program of the state's second-largest river - opening the valves for the first full day on Friday - those who know it best are debating its value and its virtue.


"There were so many salmon back then, you could fish any way you wanted, even dynamite. But when they built that dam, thousands of fish lay dead on the banks," said Imperatrice, who at age 82 still treasures his father's fishing gear. "There's no real restoration that will bring back the river I knew."



Yes, we are unlikely to ever really bring back the river from before agriculture took over this valley. But we sure can try, and this week we took a major step forward on that long arduous journey towards bringing the old salmon runs back to this damaged/heavily used river. Its an ambitious project that has (supposedly) pitted environmentalists against farmers (at least in the popular caricature, although there are farmers who are environmentalists too!) in many a legal and legislative battle over several decades - and that was before the water started flowing again! Let's see how far we can take this.


Which brings us to the week's bad news: even as the water started flowing down the river, a judge in Fresno reminded us that the battle to restore the river is far from over, when he decided that the government hadn't done enough to justify diverting water away from farmland for the sake of the endangered Delta Smelt - a tiny fish from the San Joaquin Delta that has become a symbol of the fight between "environmentalists" vs. "farmers". In hearing an appeal from some farmers against govt. rules favoring the Smelt under the Endangered Species Act, the judge didn't really raise any serious objections to the fish being listed under the ESA in the first place. Rather, he objects, oddly enough, to a lack of an environmental impact study... on humans!! You read that right - the judge wants the federal govt. to present a study of the environmental impact of saving the Delta Smelt on humans!! Talk about turning the ESA on its head! He apparently thinks that the current rules issued by the govt for water management in the delta are already causing the human environment to deteriorate: our air is fouled by dust from farms that haven't received water in the west valley, and land itself is sinking in some places due to increased groundwater pumping! As if over-irrigating and farming in arid landscapes, and careless use of underground aquifers, don't have anything to do with those environmental impacts! Those are not problems in this Cadillac Desert - but attempts to restore the natural environment for some endangered native species is what we have to worry about, because, darn it, it raises dust into our skies, and forces us to suck so much water from underground that our lands start sinking!!


And you wonder why us environmentalists always have that sinking feeling...



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Tuesday, April 7, 2009

When fishes started to walk on land and breath air

As an impressionable youth, I first saw "Life on Earth" in 1983 during my first year as an undergrad at the Institute of Science in Bombay,, pursuing a degree in zoology. And did it ever leave an impression on my mind! Of course, this was back in the days before video players, let alone DVDs. And we didn't yet have a television at home - nor do I remember the show actually being telecast in India anyway. So how did I see it? I was actually lucky enough to get to watch it projected on a big screen, with a 16mm projector whirring away quietly at the back of the big classroom. Someone at the Institute had borrowed the films for the entire series from the wonderful British Council Library! Of course, that same library which (along with the American and the Soviet ones) had already helped change the course of my life away from medical school towards zoology! Thank you Messrs. Darwin, Gould, Commoner, PGW, Steinbeck, Tolstoy... and David Attenborough. Ahh... the formative memories from those formative years. Nostalgia aside, I find it astonishing that 3 decades on, when we know so much more about the evolution of life on earth, when video technology has advanced so much, and when we have 24/7 cable channels dedicated to coverage of the living world, we still haven't seen but the one, and only, David Attenborough! Enjoy:









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Tuesday, February 24, 2009

Weird-cool bubble-headed Barreleyes like only evolution can come up with

Now here's a wonderful, bizarre discovery from scientists at our neighboring Monterey Bay Aquarium Research Institute:



Researchers at the Monterey Bay Aquarium Research Institute recently solved the half-century-old mystery of a fish with tubular eyes and a transparent head. Ever since the "barreleye" fish Macropinna microstoma was first described in 1939, marine biologists have known that its tubular eyes are very good at collecting light. However, the eyes were believed to be fixed in place and seemed to provide only a "tunnel-vision" view of whatever was directly above the fish's head. A new paper by Bruce Robison and Kim Reisenbichler shows that these unusual eyes can rotate within a transparent shield that covers the fish's head. This allows the barreleye to peer up at potential prey or focus forward to see what it is eating.



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The barreleye (Macropinna microstoma) has extremely light-sensitive eyes that can rotate within a transparent, fluid-filled shield on its head. The fish's tubular eyes are capped by bright green lenses. The eyes point upward (as shown here) when the fish is looking for food overhead. They point forward when the fish is feeding. The two spots above the fish's mouth are are olfactory organs called nares, which are analogous to human nostrils. Image: © 2004 MBARI


Deep-sea fish have adapted to their pitch-black environment in a variety of amazing ways. Several species of deep-water fishes in the family Opisthoproctidae are called "barreleyes" because their eyes are tubular in shape. Barreleyes typically live near the depth where sunlight from the surface fades to complete blackness. They use their ultra-sensitive tubular eyes to search for the faint silhouettes of prey overhead.


Although such tubular eyes are very good at collecting light, they have a very narrow field of view. Furthermore, until now, most marine biologists believed that barreleye's eyes were fixed in their heads, which would allow them to only look upward. This would make it impossible for the fishes to see what was directly in front of them, and very difficult for them to capture prey with their small, pointed mouths.


And what's more, the researchers got them on video too - look below the fold:



Robison and Reisenbichler used video from MBARI's remotely operated vehicles (ROVs) to study barreleyes in the deep waters just offshore of Central California. At depths of 600 to 800 meters (2,000 to 2,600 feet) below the surface, the ROV cameras typically showed these fish hanging motionless in the water, their eyes glowing a vivid green in the ROV's bright lights. The ROV video also revealed a previously undescribed feature of these fish--its eyes are surrounded by a transparent, fluid-filled shield that covers the top of the fish's head.


Most existing descriptions and illustrations of this fish do not show its fluid-filled shield, probably because this fragile structure was destroyed when the fish were brought up from the deep in nets. However, Robison and Reisenbichler were extremely fortunate--they were able to bring a net-caught barreleye to the surface alive, where it survived for several hours in a ship-board aquarium. Within this controlled environment, the researchers were able to confirm what they had seen in the ROV video--the fish rotated its tubular eyes as it turned its body from a horizontal to a vertical position.


In addition to their amazing "headgear," barreleyes have a variety of other interesting adaptations to deep-sea life. Their large, flat fins allow them to remain nearly motionless in the water, and to maneuver very precisely (much like MBARI's ROVs). Their small mouths suggest that they can be very precise and selective in capturing small prey. On the other hand, their digestive systems are very large, which suggests that they can eat a variety of small drifting animals as well as jellies. In fact, the stomachs of the two net-caught fish contained fragments of jellies.


After documenting and studying the barreleye's unique adaptations, Robison and Reisenbichler developed a working hypothesis about how this animal makes a living. Most of the time, the fish hangs motionless in the water, with its body in a horizontal position and its eyes looking upward. The green pigments in its eyes may filter out sunlight coming directly from the sea surface, helping the barreleye spot the bioluminescent glow of jellies or other animals directly overhead. When it spots prey (such as a drifting jelly), the fish rotates its eyes forward and swims upward, in feeding mode.


Barreleyes share their deep-sea environment with many different types of jellies. Some of the most common are siphonophores (colonial jellies) in the genus Apolemia. These siphonophores grow to over 10 meters (33 feet) long. Like living drift nets, they trail thousands of stinging tentacles, which capture copepods and other small animals. The researchers speculate that barreleyes may maneuver carefully among the siphonophore's tentacles, picking off the captured organisms. The fish's eyes would rotate to help the fish keep its "eyes on the prize," while its transparent shield would protect the fish's eyes from the siphonophore's stinging cells.


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Friday, November 7, 2008

When a Cutthroat meets a Rainbow

ResearchBlogging.orgSubmitted by Christopher Clapp for the Evolution class.

The introduction of a known species of rainbow trout into a native population of cutthroat trout and the consequences of their contact within their environments is the focus of this study. The interaction of these two species has resulted in their study of subsequent progeny shows hybridization of the two, and thus a decline of the natural populations of cutthroat trout. The implications of this hybridization will show throughout subsequent generations, considering what is known of the native species. Metcalf uses mitochondrial and nuclear markers to determine the levels of crossing of the two species based on the nature of homozygous or heterozygous allele category. These populations of hybridization were evaluated due to the known history of the streams being studied. Trout being separated by natural geographic restrictions such as natural waterfalls or by human chemical treatment conducted in the past forms for a basis of evaluation.

The successful progeny of hybridization between the two locations is evident; however there are differences between the chemically treated streams and the naturally restricted. Interestingly enough, results show that there is a trend of the cutthroat nuclear trout alleles being more prevalent beyond the upstream barrier as expected. The mitochondrial alleles were more prevalent within the hybrid or rainbow species within the areas that direct contact has been introduced within the natural barrier stream. Our study supports the notion that natural waterfall barriers provide a refuge for pure native cutthroat trout genomes across their range (Metcalf et al 2008). In the Cony Creek population, which was subject to chemical treatment in 1984, the nuclear markers were more prevalent within the cutthroat species. This bias toward the pure cutthroat is speculated to be due to the chemical treatment of the streams to eradicate the rainbow trout populations amidst restocking the cutthroat population (Rosenlund et al. 2001). Why is the case? The allele frequency distributions and disequilibrium values suggest that hybridization has been underway for longer in Cony Creek than in Graneros Creek according to Metcalf, et al (2008). I seem to feel that introducing a chemical treatment to an environment that focuses directly on one specific species allows for a re-founding of the native species. However, there findings show the invasiveness nature of the rainbow species. Over time the cutthroat nativity would be eradicated regardless of natural barrier or chemical treatment. This poses two major problems for the environment with regard to the natural species, and the changes of fish populations within streams. The introduction of new fishes for conservation strategies not only directly affect the native population, it affects the ecosystem among other animals within the environment as well. If an aggressive population of trout that is more successful than the native, the impact on resources for the community will also be affected; the environment will be in disequilibrium.


We seem to have two intrusions of the human hand into an environment, one for the introduction of the rainbow, and one to eradicate the rainbow trout species. The study shows that there is greater fitness among the hybrids. The cross between a rainbow trout female and a cutthroat male resulted in a shorter time to hatching and the progeny had a faster growth rate and a greater abundance of yolk at hatch and emergence than the hybrids of the reciprocal cross (Hawkins and Foote, 1998). Nevertheless, the two species form a system of fertility to study the hybrid selection based on natural selection and/or the effects of human based effects in the form of conservation strategies. What is this to say for the natural selection of the hybrid species or the difference between the two, and what are the effects of the introduction on the environment? Historically fishless lakes and streams have been associated with declines in amphibians, changes in invertebrate communities and changes in nutrient cycling (Knapp and Matthews, 2000). However, there is always something to be learned from the development of a new species. The selection and fitness over such a short amount of time is interesting to evaluate within the two species.


It seems to be that the rainbow trout are invading the natural species of cutthroat, and have an effect on the native species. Why are the rainbows so successful at invading this species? What are we to learn of the intrusion of populations by human hands? Either way, I agree with Metcalf in the capacity that the evaluation of the new hybrid species will give insight into long-term conservation strategies. It seems that if we limit the studies and only hold them as individuals there will always be contradiction of the results. Conservation methods and steps may be a bit naĂŻve if you only consider one method to achieve one result. By not considering the whole picture, we are increasing our opportunity cost, and thus the potential for loss.


References:


Denise K. Hawkins, Chris J. Foote (1998). Early survival and development of coastal cutthroat trout (Oncorhynchus clarki clarki), steelhead (Oncorhynchus mykiss), and reciprocal hybrids Canadian Journal of Fisheries and Aquatic Sciences, 55 (9), 2097-2104 DOI: 10.1139/cjfas-55-9-2097


Roland A. Knapp, Kathleen R. Matthews (2000). Non-Native Fish Introductions and the Decline of the Mountain Yellow-Legged Frog from within Protected Areas Conservation Biology, 14 (2), 428-438 DOI: 10.1046/j.1523-1739.2000.99099.x


J. L. Metcalf, M. R. Siegle, A. P. Martin (2008). Hybridization Dynamics between Colorado's Native Cutthroat Trout and Introduced Rainbow Trout Journal of Heredity, 99 (2), 149-156 DOI: 10.1093/jhered/esm118


Rosenlund BD, Kennedy C, Carnowski K. 2001. Fisheries and the Aquatic management of Rocky Mountain National Park. (US Dept. of the Interior).




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