Favorite Posts of 2017

Virginia Tech Ichthyology is devoted to teaching and learning about fishes.  We posted thirty nine blog posts in 2017.   Here I review the favorite blog posts from 2017.

Sea Lamprey and the Unexpected Costs of Shipping

Sea Lamprey accessed the upper Great Lakes when shipping access was improved.  They arrived at a time when Walleye, Lake Trout, Burbot, and Whitefishes were commercially over harvested.  The added mortality from Sea Lamprey was the tipping point that led to collapse of these valuable fisheries.  Expensive control efforts continue to the present time to deal with this invader.

Oral disc of the parasitic Sea Lamprey. Photo by Cory Genovese

Shades of Gray Snapper

Gray Snapper are common on Caribbean reefs that attract large spawning aggregations.  They go by a variety of names because they do not always appear to be "gray."  Gray Snapper are often overfished.  This story of the habitat and life history of Gray Snapper emphasizes the importance of conserving both inshore seagrass and mangrove habitats as well as offshore coral reefs.

Gray Snapper. Photo by Ned DeLoach  Source 

Puzzling over Large Aggregations of Sharks

This story explores how super abundant shark aggregations in a biosphere reserve persist because they rely on spawning aggregations of groupers for energy subsidies.  This discovery illustrates the futility of single species fisheries management.  Even if no sharks were harvested from this population, the population may decline depending on conditions for other fishes outside the biosphere reserve. Conservation of fish spawning aggregations, which are often targets of exploitation can help conserve shark populations, especially if combined with shark fishing bans.

Examples of shark foraging at night on the Camouflage Grouper Epinephelus polyphekadion (A, B, and C) and the Whitemargin Unicorn fish Naso annulatus (D).  Source

Pike Killifish: A Small, Specialized Ambush Predator

The Pike Killifish is an enigma. It is the only member of the Poeciliidae family that is a specialized piscivore.  Pike Killifish live in slow-moving streams and rivers, mangrove and weedy swamps, and inlets salty bays, where they associate with abundant submersed vegetation.  Their native distribution ranges from Costa Rico north into parts of Mexico.  From a single introduction in Miami-Dade County in 1957, the Pike Killifish became established in south Florida where their wide tolerance for temperature, salinity, and oxygen level allowed them to thrive in many habitats. 

Large adult Pike Killifish. Photo by Kenneth Tse Photography

Painful Stings of the Notorious Noturus

Madtoms are diminuitive catfishes that are bound to intrigue those who encounter them.  However, their pectoral and dorsal fin spines are sharp and deliver a painful venom.  Madtoms have a paradoxical combination of the strong anti predator adaptation while being a very popular bait fish.

How cute is this Margined Madtom Noturus insignis? Be careful, it packs a painful sting.  Photo by D.J. Orth.

Mad about Madtoms

These benthic nocturnal catfish arose in eastern North America sometime in the middle Miocene (that's 23.03 to 5.33 million years before the present).  Many of the twenty nine species have small, fragmented populations and are at-risk from a variety of human activities.  Although they are seldom the subject of thorough population studies, restoration activities are more commonplace today.   Madtom species are cryptic in more ways than one.   Click here to review some madtom photos.

Mountain Madtom Noturus eleutherus have a highly fragmented distribution.   photo by Tim Lane

Sharks without Fathers, by Rasha Aridi

In this essay, Rasha Aridi explains how shark offspring can be produced without a male contribution.   In 2002 a bonnethead shark gave birth in a zoo even though it had never been kept with a male.  This "virgin shark" mystery persisted and keen observers began to investigate cases of virgin birth in captivity.  Using DNA fingerprinting, these cases confirmed that all elements of the DNA in the offspring were from the mother.   Some species of sharks can produce offspring via sexual reproduction and parthenogenesis.

Parthenogenic zebra shark pup hatched and reared by the Burj Al Arab Aquarium Team. Source. 

Pelagic Thresher Sharks are Philippine Helpful, by Maddie Johnson

A major typhoon devasted an island resort leaving little or no infrastructure.  This essay examines the response of the locals in building a tourism-based economy based on the Thresher Shark.  Fisherman who used to make their money from catching as many thresher sharks as they could now make their money from this unique eco-tourism trade.

Thresher Shark.   Photo by Hugh Ross.  Source 

Siberian Taimen: Ensuring the Survival of the River Wolf, by Spencer Bell

Hucho taimen is known to the Chinese as the "river god's daughter." Mongolians protected their rivers for many centuries in keeping with their beliefs.  Consequently, some populations of the largest salmonid in the world still remain.  Today, recreational catch-and-release fishing has replaced poaching on the remaining Taimen populations.

Three Taimen, underwater photo from Eg River, northern Mongolia.  Source. 

Bow fishing for "Rough" Fish

Rough fish is an old term that once referred to less valued fish that had yet to be processed.  Today, more anglers are targeting rough fish for sport and bow fishing is among the fastest growing new fishing pursuits.  However, fishing regulations must change with the time and the term "rough" fish need to be replaced with more appropriate language.

Bow fishing at dusk.  Photo by Jason Emmel

Climate Change and the Fishes

Fear and doom stories about climate change have led to more research and development of strategies for adapting to eventual changes.  However, the scientific investigations have revealed a complex interactions of stressors related to climate change. Although there is still much to learn, it is apparent that we need to act now to protect cole and cool water refugia.

Documented responses of fishes in the southeastern USA to climate change. Green arrows indicate an increase or earlier seasonal response, and gray arrows indicate a decrease or later seasonal response  (Lynch et al. 2016).

Endemic Fishes of the New River

In my home watershed there are 8 species of endemic fishes.  They are all cool water specialists that found refuge in the upper New River during the last ice age.  These endemic fishes have limited distributions and will be disproportionately influenced by anthropogenic changes that may occur.  Read more about these 8 species in this post to learn why the New River is a special place for fishes.

New River near Rich Creek, Virginia.  Photo by Valerie F. Orth. 

Trends in Dam Removal: Reversing Irreversible Decisions

How many dams are there in the USA?  How many dams have been removed from streams? What happens to the stream after dam removal? What are the gaps in the science of dam removal?   Learn the answers to these and other questions.

Pigg River Power Dam before (photo by USFWS) and during demolition (photo by Roanoke Times)

Pelagic Thresher Sharks are ‘Philippine’ helpful , by Maddie Johnson

The cinematic masterpiece Jaws has shaped the views of sharks in American culture from its release in 1975 to this day. Although most people know that Jaws is not an accurate depiction of shark species, it has still left a fishy taste in their mouths. Shark species in general remain under researched and mysterious to the public. They are simply known as aggressive predators that have no other purpose besides hunting for prey and swimming all day. To most, sharks are just another fish in the ocean. However, an island in the Philippines is beginning to see a different side of these large, fascinating fishes. The thesis for this essay is an exploratory view into how the amazing pelagic thresher sharks are saving a Philippian town all the while being saved from the dangers of fatal exploitation. Focusing on how the Philippian community is trying to save the pelagic thresher sharks that are threatened through overfishing and the shark fin market. This essay will be covering the ecotourism aspect and how helpful it has become, the shark fin market, the results of overfishing, and finally how the two correlate in this society as well as the rest of the world.

In 2013, a major typhoon hit the Philippines, devastating natural resources and economic infrastructure. A small island resort area named Malapascula was especially effected. The area surrounding Malapascula was crushed; cars lying on flattened buildings, fishing boats thrown out to sea, and palm trees scattered across neighborhoods with no homes remaining. However, one thing remained unharmed from the typhoon; the pelagic thresher sharks. Thresher sharks are a resilient species, as shown by their extreme survival and feeding skills. They are most commonly recognized by the extra-long top lobe of their caudal fin, used to whip and stun fish before they are eaten. The thresher sharks most often use this enhanced hunting strategy to feed from large schools of fishes (Oliver et al 2013). 

Thresher Shark.   Photo by Hugh Ross.  Source 

The thresher sharks occupy the surrounding waters around a deserted island off the coast of Malapascula; traveling daily to hunt in the shallower waters and have parasites cleaned off by other fishes. Before the tragic typhoon, natives used this opportunity to catch these sharks for their fins. All the sharks in one area made it easy for the fisherman to reach quota. After the typhoon, natives still used these sharks for fins to try and regain their infrastructure, but were somewhat unsuccessful. The main sharks currently being exploited for their fins belong to the Hammerhead genus/species. Due to the increasing market for those species, other Asian countries were more interested in buying and trading those fins. This caused a drastic decline in the market for thresher shark fins (Dearden et al 2007). With one revenue diminishing before their eyes, the natives were desperately trying to figure out a new way to bring the economy back. The native fisherman always had shark tourism as a small side business, and some slowly started to turn to that as their main business. When putting all effort into the new business idea, fisherman started to see an increase in profit. The number of tourists wanting to have shark experiences was rising almost overnight; the pelagic thresher shark tourism soon became a booming industry.

Because of the location of the sharks in their hunting ground, boats had the opportunity to bring tourists in to watch the thresher sharks without influencing their natural activities. A large diving industry also started to appear with thresher sharks, as they are not historically known to attack humans like other sharks (bull, whitetip, tiger, etc.). This cageless, viewing-only ecotourism tactic has not only helped rebuild the local economy of the island, but has also helped the thresher shark species. The natives now acknowledge that they need these large predators to help them economically, so they have halted the fishing of this shark species. Fisherman who used to make their money from catching as many thresher sharks as they could now make their money from this unique eco-tourism trade-off (Topelko et al 2005).

From a conservation standpoint, thresher sharks only make up a small amount of the shark fin market, as stated earlier. However, a problem the people of Malapascula ran into was that the sharks could still be killed off in masses because of by-catch. Their long whip like tails make it easier for them to be caught in the nets intended for other sharks. Because of this, shark fishing in the Malapascula area has stopped completely in efforts to save the shark that saved the island. However, even though this island has stopped shark fishing, other parts of the Philippines, as well as many other countries, still have open shark fishing. Even with conservation efforts led by the people of Malapascula, it’s hard to lead and inspire a change. Other islands in the Philippines are seeing the work the locals at Malapascula are putting in and seeing the benefits of these sharks. There is still a huge shark finning problem in the Philippines, as well as other Asian countries, but there has been a very slow decrease over the past few years (Constable 2016).

Not only is the relationship between the thresher sharks and the natives helping the economy, it’s also helping the ecosystem. Biodiversity is slowly returning to the surrounding area and it’s all thanks to the increased protection and health of the pelagic thresher sharks. When tourists go out to see the sharks, they’re also seeing hundreds of other species of fishes from various taxa all working together in the environment. Due to the increased safety of the sharks, they have rebounded incredibly fast, alongside of the local economy. Even though these sharks have been a staple in these waters forever, the increase in the number of sharks spotted has been noticeable, which make tourists even more excited (Constable 2016). As mentioned earlier, these sharks provide a safe tourism experience. Swimming with sharks has always been a stable tourism aspect of many countries, however, these sharks are gentle but still cool looking. This experience gives tourists a whole new view of sharks.

The relationship between the sharks and the natives can be classified as mutualistic because the native fishermen have completely stopped the harvest of sharks, which obviously has increased the numbers of the sharks. The sharks in return provide an avenue for the economic revenue the island desperately needs. For these reasons, the relationship between the parties falls under the “protection” segment of the mutualistic relationship. In the last few years, people have started to understand the importance of sharks, hopefully Malapascula can become an example for other parts of Asia where shark finning is still incredibly prevalent (Constable 2016).

In conclusion, the use of ecotourism in the form of diving and guided tours has both helped the local human economy and local pelagic thresher shark populations. The pelagic thresher shark, although very funky and fascinating, is still a shark at risk of exploitation (Topelko et al 2005).

References

Constable, H. 2016. Sharks are helping the Philippines recover from a typhoon. BBC Earth. Available at http://www.bbc.com/earth/story/20161107-sharks-are-helping-the-philippines-recover-from-a-typhoon.

Dearden, P., K.N. Topelko, J. Ziegler. 2007. Tourist Interactions with sharks. Pages 66-89, editors James E.S. Higham and Michael Luck. Marine Wildlife and Tourism Management: Insights from the Natural and Social Sciences

Oliver, S.P., J. R. Turner, K. Gann, M. Silvosa, T. D’Urban Jackson. 2013. Thresher sharks use tail-slaps as a hunting strategy. Plos One.


Topelko, K.N., P. Dearden. 2005. The shark watching industry and its potential contribution to shark conservation. Journal of Ecotourism. 4:2.

Watch That Fish Move! By Don Orth

Fishes have an amazing variety of body forms, each of which is uniquely adaptive. In many cases, the best way to understand the significance of the adaptation is to watch the fish in action. Here are a few video clips that demonstrate that form follows function.

The Tangerine Darter Percina aurantiaca  is a large darter that is common in the Tennessee River drainage.   It darts among the spaces between boulders and cobbles that form the streambed.  Watch as the Tangerine Darter makes short darting movements in this underwater video (video courtesy of  Ed Scott).  

Tangerine darter Percina aurantiaca Photo by Brett Albanese.  Source

The tail-slap

Thresher sharks (Alopias spp) use their long tail to daze, smash, or kill schooling prey fish, such as sardines.  Watch this Thresher shark hunt with its tail!   Click here for the video.  Simon Oliver and his co-investigators at the School of Ocean Sciences, Bangor University, videotaped thresher sharks and discovered that the tail-slap can be administered either sideways or overhead, depending on the alignment of the sardine bait ball.  After the tail-slap, the thresher shark turned 180 degrees and consumed the dead and/or stunned sardines.  The sequence occurs quickly, lasting only 1.13 to 3.40 seconds.  During the strike, the average speed of the tip of the thresher shark tail was 14 meters per second!

Sequence of still images of thresher shark body movements throughout the tail-slap. Photos from Oliver et al. (2013).

The Ambush

In contrast to the active tail-slap hunting strategy, gars (Lepisosteidae) are sit-and-wait predators that passively wait and then ambush prey.  This video from the clear springs of Florida show the coloration of the Florida Gar Lepisosteus platyrhincus and its dominant behavior, the sit and wait posture.   Most of the time the gar lies motionless near the water surface.  When a prey fish is nearby it will slowly stalk until its head is positioned laterally to the prey fish.  They then use a rapid sideways lunge of the head during the strike and impale the prey on the numerous sharp teeth. . This lateral lunge lasts only 25-40 milliseconds (Porter and Moto 2004). 

Florida Gar Lepisosteus platyrhincus  Source

The Jump

Fish have both a sustained and burst swimming mode. One unusual behavior is the jump, where a fish uses the burst swimming mode to leap clear from the water.  Many times I have seen the jumping behavior of Common Carp Cyprinus carpio.  However, I have no satisfactory answer to “why do carp jump?”  My favorite hypothesis is that the jumping behavior forces more oxygen over the gills. But no one really knows.  But look at that carp jump! 

Tambaqui Colossoma macropomum jump for a different reason.  In the flooded forest of the Amazon the Tambaqui jumps to eat tree fruits and nuts.  The Tamaqui deposits the tree seed after passage through the gut, thereby dispersing the seed.  Watch the Tamaqui jump to capture a fruit from a tree. 

The Camouflage Carpet

Wobegong, or carpet sharks (family Orectolobidae), are named for the ornate pattern that resembles a carpet.  Like a swimming carpet, the well-camouflaged Wobegong Carpet Shark moves along the bottom.  Watch the slow swimming camouflaged carpet shark! When it holds a single position the wobegong becomes an ambush predator and swallows prey whole.  Watch the swallower.

The Mimick

Ornate Ghost pipefish Solenostomus paradoxusmimicks soft corals, hydroids, whip corals and gorgonian corals.  The small protrusions that cover the animal's body help break outline so it blends with its complex microhabitat. Watch that pipefish!  It’s not so much the movement as the mimicry.

Ornate Ghost pipefish Solenostomus paradoxus  Source

The Beach Burrower

California grunion, Leuresthes tenuis, and the Gulf grunion Leurestheses sardinas provide a easy-to-observe beach burrowing behavior at high tide during their breeding.  You have to watch that fish.  Watch as the female grunions burrow into the sand to deposit their eggs. 

 

Grunion life cycle is synchronized by the lunar cycle where breeding occurs at high tides.  Illustration by Greg Martin

So watch the fish and learn more about their unique adaptations.   Share your observations and videos with others.

References

Oliver SP, Turner JR, Gann K, Silvosa M and D'Urban Jackson T  2013.  Thresher sharks use tail-slaps as a hunting strategy. PLoS ONE, 8 (7): e67380.http://dx.doi.org/10.1371/journal.pone.0067380

Porter, H.T. and P.J. Moto 2004. A comparison of strike and prey capture kinematics of three species of piscivorous fishes: Florida gar (Lepisosteus platyrhincus), redfin needlefish (Strongylura notata), and great barracuda (Sphyraena barracuda). Marine Biology 145:989-1000.  http://link.springer.com/article/10.1007/s00227-004-1380-0