These giant fishing spiders of North America are some of the largest true spiders on the continent sometimes capable of near 6" legspans!

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Excellent care sheet by Paul Bollinger:

Cypress and Gum and Tupelo swamps make up a large part of the Gulf Coast of the USA. Louisiana is no exception. At night the swamps in the Pearl River Drainage in Southeast Louisiana come alive with all forms of life. Moths, Beetles, Crickets appear everywhere. Bats swoop in and out the spotlight taking advantage of the congregation of insects in the light. The swamp is full of examples of one species bowing down to another, completing an elaborate cycle of life and death. One can’t help but admire the amount of death and rebirth that takes place, in one night, in this habitat. I find myself considering the swamp to be one large life form, with little intricate synapses happening on an incomprehensible level. It’s truly amazing to witness this life force at work.

Sitting comfortably atop the invertebrate apex in the Pearl River Swamp are undoubtedly, “The Fisher Spiders.” Fisher spiders fall under the family Pisauridae which contains the genre’s Dolomedes and Pisaurina. This care sheet will cover the Arboreal species of the genus Dolomedes occurring in the SE United States. Specifically, The Dusky Fisher Spider (Dolomedes tenebrosus).

Unfortunately there is not much info available on this genus, or at least not available to non-academia, so these are the observations of a layman. They are not scientific but they are real observations.

I would argue that the D. tenebrosus and D.okeefinokensis make up the largest of the true spiders in North America. These are the unknown Monsters of the Swamp. Specimens in excess of 5” leg spans are not uncommon and unverified reports of specimens up to 8” exist. I typically don’t believe fish stories, snake stories or even spider stories, but in this case I have personally witnessed spiders with leg spans of at least 6” that were out of my reach. So the prospect of such a large true spider really excites me.

The Cypress trees that the largest spiders inhabit have bases comparable to two cars parked next to each other. If there are hollows and retreats extending 30 feet up in the tree then there are giant spiders that high up the tree. I never find them on the ground. They are always sitting in ambush position on a tree or root or Cypress knee.

Fisher spiders in the genus Dolomedes eyes’ are oriented forward on the cephlathorax. This makes detection tricky. This spider is typically facing down the trunk of the tree.

This orientation seems necessary for predation of fish and other invertebrates. However I find very few of these spiders with fish as prey. Dolomedes triton is commonly seen with fish as prey, where the D. tenebrosus is most frequently seen with moths, beetles and often members of their own species.

Cannibalism is common in this species. I haven’t noted whether this was post-copulation Cannibalism of males by females, or if this was merely an opportunistic feed. I will say that most of the cannibalism that I have witnessed was by larger spiders 3”-4” Leg span. (Note: Todd Gearheart has reported that he kept 40 Dolomedes spp. in a 40 gallon tank with multiple cork bark shelters and kept them well-fed for over a month without a single loss, so in captivity, under those conditions, they can be quite communal).

“The reproducing of lost organs- the reproducing of legs that have been lost by immature spiders is frequently observed. If a leg lost by a young spider the wound soon heals, and at the succeeding mount the bud of a new leg appears this bud increases in size at each succeeding moult; and in time if the process begins early enough in life for the spider then a functional leg is obtained.” - Comstock

Life Cycle:

“At the beginning of the 20th century the conventional wisdom about araneomorph
spider life-cycles was that most were annuals, either spring breeders or summer-autumn breeders (Emerton 1902). Palmgren (1939) provided one of the first exceptions when he
described the two-year cycle of Dolomedes fimbriatus (Clerck 1757) where juveniles
over wintered twice. “-2001. The Journal of Arachnology 29:367–377

I believe that the Dusky Fisher Spider (Dolomedes tenebrosus) occurring in Louisiana can live for over two years and possibly even 3 years in captivity. I only find large females specimens around Bald Cypress (T. distichum) trees that are large with hollows. Lack of hibernacula certainly seems to coincide with lack of large spiders. This seems to be a rule. I believe that these trees serve as hibernacula during the winter months and prime-time hunting during the spring and summer.

Handling:

I do not recommend that ANY spider species is handled. I know it sounds paranoid, but I have been bitten in the field by Scolopendra and Dolomedes and I don’t like it. Therefore, I advise people to only hold what they are willing to take a bite from. Plain and Simple- On that note, this is not a medically significant spider. I suffered a bite on the neck from a 2” D. tenebrosus while swimming in a cypress bayou. I was unaware of it’s presence until I smashed it on my neck then I was bitten. I experienced localized pain and minor swelling followed by light lymph secretion, very localized tissue damage along the lines of a large pimple, and no lasting effects or even a cool scar.

As far as disposition, I find them to be fairly non-defensive. The flight response must be the most successful response in their habitat because it is almost always the reaction to my intrusion. In fact, when I handle them (gloved) for capture, they do not seem outwardly aggressive. They are fast spiders when they want to be but most of them seem to sit and wait. I would say that they are a good notch down from the Heteropoda (Huntsman) species that I’ve worked with.

Breeding: I have not successfully bred this species but will amend this section once successful breeding is accomplished.

Housing:

A large spider can be set up in a 10gallon Tank with a screen lid. This spider is incapable of climbing glass and other smooth surfaces. Cork board adhered to the back of the tank will serve as a platform for your spider to hunt and rest. Keep in mind this species is absolutely arboreal meaning that it lives in or on trees. A retreat is nice and will make your spider feel more secure in its new habitat. They do not require water as substrate in the enclosure but it will help maintain the humidity levels and it makes for easier cage cleaning. Tannic acids (Tea Color in Water) given off by the bark are not a problem. These spiders come from a very acidic habitat. This will also cut down on any fungal growth in the cage. Cypress mulch as a substrate works well too. A light can be used to create a temp gradient in the cage but is really unnecessary considering they are a nocturnal spider. I have witnessed specimens feeding in hollows during the daytime though.

Housing for sale:
This method has worked well for me:
A piece of bark (corrugated cardboard can be used but they love Oak bark) in a 32oz container is sufficient. Water can be added to the bottom of the container until there is ½” in the bottom. A hole at the water level will keep you from having to interact with your spider during each cleaning. Simply tip the container to pour out the water and refill through the same hole.

Temps:
70Low-90High

Food:
I feed Fisher spiders all types of invertebrates. They seem to like roaches and moths but will readily accept anything that is moving and of comparable size. It would not surprise me if these spiders might feed on bats (mammal moths) when they get larger 6”+!

All in all, I think this is a much overlooked true spider. In the race for the biggest and the best, Well at least when it comes to North American true spiders, the trophy goes to the giant Dolomedes of the Pearl River Swamp. This is a real enjoyable species to keep.

Care sheet by:
Paul Bollinger
BayouSurreal