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Brachiopsilus dianthus (Last & Gledhill 2009)

Pink Handfish

Geographic Range

The Pink Handfish, Brachiopsilus dianthus, is among a small group of marine fishes with a limited geographic range. In the family, Brachionichthyidae, these handfishes consist of fourteen species that are predominantly distributed in southeastern Australia (Last & Gledhill, 2009). Amongst the four endangered species of this family, Pink Handfishes are the only endangered species that reside in shallow marine waters. In southeastern Australia, this fish species is constrained to Tasmania, typically in temperate waters (Stuart-Smith et al., 2020).

Brachionichthyidae are entirely endemic to Australia and are known to have the narrowest geographic distribution out of the region’s abundant fish species. Most of the species in this family are poorly studied. This is a result of the unique nature of the fish species as most of them are restricted to extreme depths due to their lack of swim bladder (Stuart-Smith et al., 2020). Rather than swimming long distances, this family prefers to walk along the seafloor. Early fossil records suggest little morphological change over the phylogenetic lineage of handfishes (Last & Gledhill, 2009), but their behavior has been connected to the structure of their pectoral fins. The handfishes’ pectoral fins resemble the form of human hands (Carnevale & Pietsch, 2010).

Habitat

Like all handfishes, the Pink Handfish is endemic to Australia (Last & Gledhill, 2009). Most handfishes are demersal but the Pink Handfish prefers to be in relatively shallow waters compared to other handfish species. This fish species has been found to be most abundant in Tasmania. Typically found between fifteen to 38 meters underwater, it was thought that the Pink Handfish’s ecological range varied much less than its Brachionichthyidae counterparts. But, in 2021 the fish was found at a much deeper depth of around 120 meters which may extend its original range. As the fish is lacking a swim bladder, it moves about the soft ocean floor and tends to stay near harder substrates, which are used for anchoring its clutches of eggs (Stuart-Smith et al., 2020).

Physical Description

According to the Pink Handfish’s holotype, the coloration of the fish has been observed to have red and pink splotches throughout its body with bluish black eyes. The mouth is narrow. The fish’s belly and lower jaw is a lighter pink while reddish brown margins can be seen on the rayed portion of its fins. Compared to the pectoral fins and dorsal spines, the caudal fin and anal spine is much lighter in coloration but has similar dark markings on the rays (Last & Gledhill, 2009). Similar to anglerfishes, the Pink Handfish possesses a pink illicium; however, the illicium of this species is much shorter. This could be due to the lack of reliance on this physical trait since the Pink Handfish resides in shallow waters. Typically, the illicium is used to lure prey, but the lack of observations on Pink Handfish limits available information on its use of the illicium. Behind the illicium, the Pink Handfish has a triangular, modified dorsal spine on its head while the second dorsal spine is more rectangular. The dorsal spines of the species are between 19 to 21 while its anal spines are from 9 to 10 spines. As previously mentioned, the pectoral fins has similar resemblance to human hands, which they use to “walk” across the seafloor (Whitley, 1949). This behavior is also due to their lack of swim bladder (Carnevale & Pietsch, 2010). In preservation, the holotype has a white, yellowish green or pink coloration. The dark markings on its rays are more evident in the holotype’s fins. All paratypes have been found to similar reddish brown streaks on the dorsal and caudal fins. Although not much is known about this species, the largest size observed has been around 99.5 mm while the smallest specimen was measured to be 68.5 mm (Last & Gledhill, 2009).

Development

The female Handfish tends to spawn between the months of September and October. It chooses vertical objects to lay its eggs on sea grasses or substrates near the bottom. The mother will guard its eggs as it waits for the clusters to hatch. The Handfish does not typically lay a large number of eggs, but they do have the advantage of not experiencing the pelagic larval stage.

Reproduction & Life Span/Longevity

Handfish young spend the first 7-8 weeks of their lives in their eggs as their mother guard them from predators. Once they are hatched, the young will live and grow near the seafloor. They will remain there until their size has grown about half of their mother. The lifespan of the Pink Handfish is currently unknown as there are no known subjects kept in captivity or tagged (Last & Gledhill, 2009).

Food Habits

Since the Handfish lacks a swim bladder, it spends its time patrolling the sea floor looking for meals. The main way the Handfish seeks to capture prey is with its modified dorsal spine which is used as a lure (Last & Gledhill, 2009). Handfish have been seen camouflaging themselves under the ocean floor they patrol to better trick its unsuspecting prey. The modified dorsal spine resembles a smaller animal that then lures other prey near the fish’s camouflaged mouth. Relatively small, the Pink Handfish tend to prey on organisms smaller than them found on the seafloor, such as polychaete worms. Given the elusiveness of this species in particular, it is hard to determine what they may eat. Since limited specimens are caught whole, the contents of their stomachs can not be further studied.

Predation

The lack of long-term studies of the Tasmanian benthos limits how much is known about the Pink Handfish. In 1999, the last reports recorded that the fish species is mainly threatened by habitat degradation, scallop dredging, pollution, and invasive species (Stuart-Smith et al., 2020). Compared to other species of handfishes, the Pink Handfish resides in shallow waters, so specific threats are still poorly researched.

Ecosystem Roles

Due to the absence of long-term studies of local Tasmanian marine benthos, the nature of the subtidal environment remains unknown because we are unsure how the ecosystem was prior (Edgar & Samson, 2004; Dayton et al., 1998). This limits how much we know the environment has changed over time. The role of the Pink Handfish is debated since it has not been captured interacting with other fish much. It does benefit the ecosystem by eliminating some parasitic worms that have been known to attack mollusks. These fish also compete with some corals that also occupy its territories. For the most part, this small fish species is used as prey for larger predators.

Economic Importance

The Pink Handfish is not high in commercial demand as the species is rare to find among the Australian and Tasmanian waters. Although the fish has been captured as a result of bycatch from scallop fishing, the endangered species cannot be kept. Therefore, the species is not profitable. The Handfish does positively impact the economy by its consumption of polychaeate worms. Between 1969 and 1995, a long term study of Port Philip Bay found a decline in mollusc species richness due to fishing exploitation (Wilson et al., 1998). Studies have discovered losses in molluscs associated with dredging has led to a synchronous increase in the polychaeates and crustacean populations (Currie & Parry, 1999; Bradshaw et al., 2002). These worms are known for boring into mollusks, which can lead to commercial loss for fisheries and independent fishermen. In the 1800s, the Pink Handfish being found as a bycatch in scallop dredging may be an indicator that the species was preying on the parasitic worms that affected the mollusk populations (Edgar & Samson, 2004). As Tasmania possesses a rich molluscan biodiversity, the gradual change in the regional population could have been contributed from multiple factors.

Conservation Status

As of now, the Pink Handfish has officially been deemed Endangered by the IUCN (Hudson & Mace, 1996). Following 20 years of elusivity, the first specimen of the Pink Handfish was found in 2021 by a crew of researchers in Tasman Fracture Marine Park. With its new designation as “endangered”, it would now also be protected by international law from fishing and purposeful capture. After the first specimen was located in a protected marine park, the rest of the undisturbed population would be protected under Australian environmental law.

References

Bradshaw, C., L. 0. Veale, and A. R. Brand. (2002). The role of scallop-dredge disturbance in

long-term changes in Irish Sea benthic com-munities: a re-analysis of an historical

dataset. Journal of Sea Research 47:161-184

Carnevale, Giorgio, and Theodore W. Pietsch. (2010). “Eocene handfishes from Monte

Bolca, with description of a new genus and species, and a phylogeny of the family

Brachionichthyidae (teleostei: Lophiiformes).” Zoological Journal of the Linnean

Society, vol. 160, no. 4, 2010, pp. 621–647, 24 November 2010. No

https://doi.org/10.1111/j.1096-3642.2009.00623.x.

Currie, D. R., and G. D. Parry. (1999). Changes to benthic communities over 20 years in Port

Phillip Bay, Victoria, Australia. Marine Pollution Bulletin 38:36-43.

Dayton, P K., M. J. Tegner, P. B. Edwards, and K. L. Riser. (1998). Sliding baselines, ghosts and

reduced expectations in kelp forest communties. Ecological Applications 8:309-322.

Edgar, GJ and Samson, CR. (2004). Catastrophic decline in Mollusc diversity in eastern

Tasmania and its concurrence with shellfish fisheries. Conservation Biology 18:

1579–1588.

“Eschmeyer"s Catalog of Fishes.” CAS - Eschmeyer’s Catalog of Fishes:, California Academy of

Sciences, researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp.

Hudson, Elodie, and Georgina M. Mace. "Marine fish and the IUCN Red List of threatened

animals. Report of the workshop." (1996).

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Cambridge, UK. (2012)

Last, Peter R., and Daniel C. Gledhill. “A revision of the Australian handfishes (lophiiformes:

Brachionichthyidae), with descriptions of three new genera and nine new species.”

Zootaxa, vol. 2252, no. 1, 2009, pp. 1–77, https://doi.org/10.11646/zootaxa.2252.1.1.

Stuart-Smith, Jemina, et al. “Conservation challenges for the most threatened family of marine

bony fishes (handfishes: Brachionichthyidae).” Biological Conservation, vol. 252, 9 Nov.

2020, p. 108831, https://doi.org/10.1016/j.biocon.2020.108831.

Whitley, G.P., The handfish The Australian Museum Magazine, 9 (1949), pp. 398-403,

https://doi.org/10.3853/j.0155-3496.1949.9.12

Wilson, R. S., S. Heislers, and G. C. B. Poore. 1998. Changes in benthic communities of Port

Phillip Bay, Australia, between 1969 and 1995. Marine and Freshwater Research

49:847-861 Brachiopsilusdianthus (talk) 04:21, 26 November 2023 (UTC)