fish parasites

[williehookem]

New U of A study says sea lice from fish farms could wipe out wild salmon

Fish on some B.C. rivers could be extinct in four years


Jeff Holubitsky, edmontonjournal.com

Published: Thursday, December 13, 2007
EDMONTON - Unless fish farms change their practices, sea lice could drive British Columbia's wild pink salmon on some rivers to extinction within four years, a new study led by a University of Alberta fisheries ecologist says.
"This is the first time we've been able to measure the impact of sea lice on wild salmon populations which turns out to be quite severe," lead author Martin Krkosek said from the U of A's Bamfield Marine Science Centre on the west coast of Vancouver Island. "It showed that if these sea lice infestations continue these populations are going to slide away to extinction."
The peer-reviewed study appears Friday in the journal Science.
http://a123.g.akamai.net/f/123/12465/1d/media.canada.com/51df8522-e0a5-44bf-ad15-5fc7d54dfa34/fish,lice,farm.jpg?size=lYoung pink salmon infested with sea lice.




The study examined wild salmon populations in a coastal area between Vancouver Island and the mainland , known as the Broughton Archipelago north of Vancouver. It is the site of seven streams where wild salmon spawn and also about 20 primarily Norwegian-owned Atlantic salmon farms holding between 500,000 to 1.5 million fish each.
"The patterns of sea lice infesting juvenile salmon near salmon farms has been documented not only in the Broughton, but in other areas of British Columbia and also in Norway, Ireland, Scotland and Canada," Krkosek said . "But nowhere has it been possible yet to measure the impact on the wild salmon population."
Previous U of A studies confirmed the parasites could spread from farmed to wild salmon and that many juvenile wild pink salmon were not surviving because of the parasites which eat the young fish alive may also transmit other diseases.
The latest study estimates 99 per cent of pink salmon in the area could be wiped out within four years.
"That's functionally extinct," Krkosek said. "We were expecting to see and impact, but we were quite surprised at how severe it was."
The natural-occuring sea lice larvae, which are concentrated in the dense numbers of Atlantic salmon in fish farms, attack tiny salmon as pass as close to 15 kilometres of fish farms. The effect appears particularly devastating when the open-net farms are located close to spawning streams.
Ironically, fish farm salmon appear to get the lice from wild salmon returning from the open ocean to spawn and return the favour as the wild young fish swim past on their journey to the ocean.
Krkosek said solutions to the problem could include moving fish farms to deeper open water or designing closed pens with pumps and filters that keep the farmed salmon from having contact with the outside water.
"Certainly the technology exists," he said.

[williehookem]

http://www.iphc.washington.edu/halcom/images/lice.jpgThe Problem with Fleas

By Steve Kaimmer

Sand fleas are parasitic crustaceans common throughout the North Pacific. They are amphipods, rather than copepods. They attach themselves to other water creatures by digging into the flesh or scales and eat at the animals they are attached to. Small fish, swordfish, sunfish, flying fish, starfish, and even whales are attacked by the different kinds of parasitic crustaceans.

Flea size can vary from as small as a short grain of rice to 3 or 4 times larger. Their distribution is spotty, and they seem to be more common on sandy bottom. ‘Hot’ spots in their distribution may change from season to season or year to year. These may be very localized, such that a part of a set can be severely impacted by fleas, while another part shows no damage. Fleas appear to be more active at night, and the effect on captive fish is also more evident on longer sets. These seem to be additive, so that a long night set might have worse predation than a short night set, etc.

Flea predation starts with the presence of fleas on the surface of the body. They appear to first remove (eat?) the slime, then the top layer of the skin. The fleas seem to enter the body first through holes eaten through the skin membrane either near the eye, anus, or dorsal fins. First evidence of fleas (other than their physical presence on the body) can be a non-glossy whitened appearance in these areas where the slime and scales have been eaten. This is still a non-fatal condition.

Once the fleas have penetrated the body, we consider the fish to be dead. Penetration near the anus or eye is often evident by the presence of a hole about .25 centimeter in diameter. Fleas entering in these locations probably go first for the ‘sweet meats’ at the base of the gill attachments or the gonads. Halibut are quickly consumed once fleas invade. The membranes of the dorsal fins are often eaten, and entrance holes can be seen near their base. The dorsal and/or anal fin membranes may be eaten away, leaving fin rays exposed. Skin on the body is separated from tissue where sand fleas have eaten.

At this stage, moving bumps can often be seen under the skin near the dorsal fin where fleas are moving about. After eating sweetmeats and gonads, the blood from the bloodline below the spine and from the gill arches disappears. The fleas then consume the muscle tissue. At this point, a fish may still be attached to the hook and a bag of skin and bones may be retrieved on the longline. From observations of halibut caught by pots and attacked by fleas, the skin seems to be the last thing eaten.

[williehookem]

Introduction to the Branchiura

Fish Lice!


http://www.ucmp.berkeley.edu/arthropoda/crustacea/images/branchiura3.jpghttp://www.ucmp.berkeley.edu/arthropoda/crustacea/images/branchiura2.jpg
Left: dorsal view of branchiuran Argulus japonicus
Right: ventral view of branchiuran Argulus japonicus, courtesy of David Allard (TAMU)

The Branchiura are a parasitic crustacean group of uncertain relationship within the Maxillopoda (http://www.ucmp.berkeley.edu/arthropoda/crustacea/maxillopoda.html). They are thought to be an ancient group but there are no known fossils. There are approximately 130 species described currently, all of which are ectoparasites (http://www.ucmp.berkeley.edu/arthropoda/crustacea/parasitism.html) (attach to the outside of the host) on fish. A few exceptions have been found attached to amphibians.

The branchiurans' very flat, oval body is covered almost completely by their broad carapace with unusual, prominent compound eyes. Branchiuran mouthparts and antennae are modified for their parasitic lifestyle and form a proboscis with hooks, spines, and suckers. They are capable of leaving their host for up to three weeks.

Branchiurans leave their hosts for several reasons: to find a different host, to mate, and to lay eggs. When they locate a new host they grab a hold, scurry toward the head, and attach behind the operculum (the flap that covers a fish's gills) or a fin.

Attaching in these slightly protected areas reduces the likelihood they will be brushed or washed off of the host. Once attached to the host they either pierce the hosts skin and suck blood and other internal fluids, or they feed on mucus and skin sloughed off by the host. Sever infestations can devastate and aquarium. They can move very fast which is rather disconcerting when watching a swarm in your aquarium.





I think these suckers can be pretty bad! :scared:

[williehookem]

Fish Lice /Gill Lice - What are they?


By Rudy Lukacovic

http://www.dnr.state.md.us/fisheries/art2002/100202ergasilus.jpgFishermen catching striped bass (as well as other species) in Chesapeake Bay may sometimes observe external parasites on the skin or gills of the fish they land. There are numerous species of external and internal parasites that can infect striped bass and other fish. These organisms occur naturally and under most circumstances do no great harm. More than 45 species of parasites and other microorganisms have been identified from Chesapeake Bay striped bass.
The gill lice (Ergasalis) are the most abundant and prevalent parasite of inland and coastal marine populations of striped bass. They are a parasitic copepod. Copepods are small, sometimes microscopic, invertebrates that are members of the plankton community. Heavy infestations of Ergasalis have occasionally been reported from the vicinities of Baltimore, Philadelphia and Washington DC. Frequently anglers conclude that striped bass with these parasites on their gills are fish newly arrived http://www.dnr.state.md.us/fisheries/art2002/ergasilusgill.jpgfrom the ocean. In fact, the life span of Ergasalis actually decreases when salinity reaches marine concentrations of 32 parts per thousand (ppt). High salinity also exhibited some detrimental effect on Ergasalis egg survival. Ergasalis reproduction and infestation of striped bass takes place throughout the bay in salinities varying from 0.5 to 30 ppt.

Females parasites remain attached to the gills of fish throughout the winter. Ergasalis egg sacs appear during January and newly attached larvae are found in April. Juvenile striped bass can become infected as early as their third month of life while still in their natal rivers.

As the fish increases in size so does infection intensity. Highest counts of full sized female Ergasalis were seen in late April and early May and again in June and in October. In any school of striped bass, many copepods may be just on a few fish.

Different species of Ergasalis may be specific to each species of fish. Ergasalis has been reported infecting largemouth bass and bluegill sunfish in freshwater lakes in Alabama. It has also been reported from striped bass in a freshwater lake where a heavy infestation may have caused sufficient stress for a bacterial disease to become established.

Other external parasites are occasionally observed on striped bass. Two other common external parasites are Argulus, the fish louse, which is another copepod like Ergasalis, and Lironeca, an isopod.

http://www.dnr.state.md.us/fisheries/art2002/argulus.jpgArgulus, the fish louse, is small, round and flattened. It is found on the skin and scales of striped bass http://www.dnr.state.md.us/fisheries/art2002/argulusOhiostate.giffrom August to October. Its prevalence peaks in August. The presence of Argulus on striped bass can be coincidental with the appearance of small lesions on the base of the tail. It was also found on the skin of freshwater fish in Alabama.

Lironeca is a rather large isopod and its body is flattened top to bottom. It is commonly seen on the gills of striped bass, as well as on Atlantic menhaden and bluefish. It is mostly seen in the summer months at higher salinities.

There are numerous other parasites that are found internally in striped bass from protozoans to worms. These organisms are a normal part of environment in which all fish live. Under most circumstances they are tolerated by the fish but occasionally heavy infestations can be detrimental, leading to weakened immune systems and possible subsequent infection from bacteria and viruses.

Any concerns regarding human consumption of normal appearing fish can be addressed by proper cooking. Any disease or parasite will be killed during the normal cooking process.

This does not apply to shellfish caught from areas closed due to pollution, or to finfish which are under consumption advisories because of tissue contamination. Common sense should be applied, and any abnormal appearing fish should not be eaten.

[VSdreams]

http://www.iphc.washington.edu/halcom/images/lice.jpgThe Problem with Fleas




At least with dogs having fleas, they can scratch a lot. Thanks for posting, I learned a lot, I think. :upck:

[voyager35]

I have mostly found gill lice on striped bass that we catch in the late summer to fall. Sea lice on the ones that come in from offshore in the spring. Next time I catch a bluefish I will have to check under the gills. I never thought of doing that with the blues as we toss most of them back unless going sharking.