Sunday, 2 January 2011

The Spotted Handfish, the Fish That Walks

Image of a spotted handfish adult
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Lophiiformes
Family: Brachionichthyidae
Genus: Brachionichthys
Species: Brachionichthys hirsutus
Conservation Status: Critically Endangered
Common Names: Spotted handfish, Prickly-skinned Handfish, Tortoiseshell Fish


The Spotted Handfish is a rare and endangered fish of the Brachionichthyidae family. The species occurs exclusively in south-eastern Australia, in the lower Derwent River estuary, Frederick Henry Bay, D'Entrecasteaux Channel and the northern Storm Bay region.

This strange animal is best known for using its hand-like fins to "walk" on the sea bottom instead of...swimming!

You can see the species' distribution in Australia in the map below. It is based on public sightings and specimens in Australian Museums.

Map showing the distribution of the spotted handfish
Spotted Handfish Distribution


Habitat & Description 
The spotted handfish is a benthic (living on the sea bottom) fish, usually found "walking" or resting in coarse to fine silt and sand, at depths ranging from 5 to 10 meters (~16 to 32 ft). However, there have been recorded sightings at depths of up to 30 meters (~98 ft).

The species has a small, pinkish to white, pear-shaped body that is covered by small spines and black, brown and orange spots with orange borders. These markings are different and unique from individual to individual. Adults have an average length of about 12 cm (~4.7 in).

This unusual fish has highly adapted pectoral fins that look like hands. The fins are used like limbs, enabling the fish to walk on the sea bottom. B. hirsutus is remarkably slow and can easily be approached by divers. (Note:another notable example of walking fish you may want to check is Ogcocephalus Darwini,commonly known as the red-lipped batfish.)

B. hirsutus is capable of swimming clumsily, using its tail and anal fins.


Beautiful picture showing a spotted handfish resting on the ocean floor


Diet 
The species feeds by sucking in prey items. In the wild, they have been reported to eat crustaceans, polychaete worms and small shells. Captive specimens in aquaria have been observed to eat mysid shrimp, amphipods, and small live fish. Hatchlings do quite well on a diet based on small amphipods.


Credit: Rick Stuart-Smith / Reef Life Survey


Reproduction 
Spawning takes place from September to October. Females lay an interconnected egg-mass of 80–250 eggs, usually on vertical objects, like:
  • Sea grasses 
  • Sponges 
  • Stalked ascidians 
  • Macrophytic algae 
  • Polychaete worm tubes 

After laying the eggs, the female stays with them and guards them until they hatch, 7 to 8 weeks later. The spotted handfish lacks the larval stage and hatchlings arise as fully formed, miniature adults (6 to 7 mm long), which move straight to the sea floor. The newborns appear to remain in the vicinity of spawning throughout their life.



As shown in the video, the species is easily approached and photographed


Conservation Status & Possible Threats & Conservation Measures
The species used to be a relatively common sight until the mid 1980s, especially in the lower Derwent River estuary. Since then, there has been a massive decline in their overall population. Today, the Spotted Handfish is classified as critically endangered, both by the IUCN and the ASFB Threatened Fishes Committee.

Notably, there were only two recorded sightings between 1990 and 1994. This catastrophic decline led to the formation of the Spotted Handfish Recovery Team in 1996, which consists of a number of government agencies that aim to protect this strange animal. The team's interests include research on current wild populations and breeding under captivity. The organization work is quite encouraging, having managed to breed the species multiple times in captivity. One of their ultimate goals is to sometime start reintroducing populations - bred under captivity - back to their natural environment.

It is believed that one of the main reasons behind the species dramatic decline is the introduction of the northern Pacific seastar (Asterias amurensis). These seastars are voracious predators of shellfish and data indicates that they eat the eggs of the spotted handfish or the sea squirt, on which the handfish many times attaches its eggs.

Image showing an adult Northern Pacific seastar (Asterias amurensis)
Northern Pacific seastar 

Some other factors that have probably contributed to the species' decline may be:
  • Predation and fishing 
  • Habitat modification and deterioration 
  • Heavy metal contamination 
  • Reduced numbers of benthic organisms which are suitable for attaching their eggs
  • The increasing numbers of the Electroma georgiana oyster that attaches to its egg masses, largely destroying them in the process. 

The species is currently protected by Tasmanian law and the Common wealth's Environment Protection and Biodiversity Conservation Act 1999



Video showing a spotted handfish, slowly walking on the ocean floor

4 comments:

  1. I agree..................you have helped alot though!!

    ReplyDelete
  2. Wow so true!

    ReplyDelete
  3. The fish in the video is a frogfish

    ReplyDelete
    Replies
    1. Indeed, the video features another species of fish. Removed and replaced with a proper video

      Delete