Issue 26, ah blessed 26. But why is this issue so special? Well not only is it Shark Week (apparently) but it is also half a year since a rather unassuming blog appeared on the off-topic page, in other words this one. As such I would like to say a big thank-you to everyone and anyone who has ever read and commented on this series.

Many Thanks

Impurest Cheese

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Issue #26 - Daggernose Shark

Kingdom – Animalia

Phylum – Chordata

Class – Chondrichthyes

Order – Carcharhiniformes

Family – Carcharhinidae

Genus – Isogomorphodon

Species – oxyrhyncus

Related Species - Daggernose Sharks are a member of the Requiem Shark Family which includes the Tiger Shark (Galeocerdo cuvier) (1)

Range

Murky Waters

The Daggernose Shark is a small shark that grows up to a meter and a half in length and around thirteen kilos in weight. Like other Requiem Sharks, the Daggernose has a streamlined body designed for short bursts of speed rather than prolonged high speed chases. In addition the Daggernose has a more pronounced, almost blade like snout that is packed with additional electro-sensitive receptors to aid in navigation and prey detection in muddy waters. Due to it’s preference for muddy waters the eyes of the Daggernose are smaller than sharks of a similar size found elsewhere in the world (2).

The Daggernose hunts on small fish, often making runs into shoals of fish to injure its targets, before coming back around to finish them off, with an extendable pair of jaws and rows of small needle like teeth. Adult Daggernose Sharks are outside the size range of other coastal predators although the young are prey to both the Bonnethead (Sphyrna tiburo) and the Smalltail Shark (Carcharhinus porosus). Despite being a coastal species the Daggernose is intolerant to large quantities of fresh-water and during the Wet Season, moves away from river mouths and mangrove forests.

Despite being harmless to humans, the Daggernose shark is still hunted in some parts of its range. Gillnetting in particular, is dangerous to the Daggernose and it makes up one tenth of the bycatch found in North Brazilian fisheries. Official records show a ninety percent decline in the last decade due to overfishing and a slow reproductive rate with the ICUN classifying the species as Critically Endangered (3).

Conservation Crisis: Five to Save #2 - Cartilaginous Fish

Imagine the scene, the oceans deadliest predator is on the prowl, scanning the surface of the water waiting until, prey in range it strikes before dragging the victim up to a slow and cruel fate. But this creature is no giant predatory shark but rather Mankind and its voracious hunt for more and more resources. Being competition for the sea’s bounty it’s no surprise Sharks and Rays (as well as their close allies the Sawfish and Guitarfish) are some of the most endangered animals on the planet. In fact it’s estimated that 1 in 4 species of Shark and Ray are either listed as Vulnerable or Endangered. As such the list was expansive so I chose five that highlighted different threats faced by these majestic ocean masters. (4)

Angel Shark (Squatina squatina) - Critically Endangered

Threats - Commercial Fishing: Large scale fishing operations of the Angel Shark or Monkfish are nothing new but recently fish stocks have been declining rapidly. Coupled with low reproduction rates the Angel Shark is extinct in some parts of its range although efforts by UK Government to preserve the species, within its waters, have had some limited success

Common Guitarfish (Rhinobatus rhinobatus) - Endangered

Threats - Fin Fishing: Due to it’s placid nature and because it inhabits shallow water the Common Guitarfish is an easy target for shark fin fishing expeditions. During 1994 and 1999 the species was declared extinct in its Northern Part of its range despite an overwhelming abundance just fifty years previously.

Ganges River Shark (Glyphis gangeticus) - Critically Endangered

Threats - Pollution: As one of six freshwater sharks, the Ganges Shark faces problems with acute industrial pollution and river dams not found in oceanic species. In addition the species is unjustly persecuted due to misidentification with the Bull Shark (Carcharhinus leucas)

Giant Devil Ray (Mobula mobular) - Endangered

Threats - Bycatch: The only species of Manta Ray found in British Waters suffers from accidental persecution from commercial fisheries. Devil Rays often get caught in nets and lines set for smaller fish and eventually exhaust themselves after fighting to free themselves for hours, maybe even days before dying. Captured specimens are often thrown back since there is no commercial value in the species.

Giant Freshwater Stingray (Himantura polylepis) - Endangered

Threats - Sport Fishing: Adult Giant Stingrays are a prized sport fish, due to their size and tenacity when hooked. Unfortunately the species is often damaged after being hooked and, since there is no commercial value for the species, often returned to die a slow agonising death in the river. The Thai Government is, at current, maintaining a captive bred population but wild release has not yet been scheduled.

Bibliography

1 - www.arkive.org

2 - Fowler, S.L., R.D. Cavanagh, M. Camhi, G.H. Burgess, G.M. Cailliet, S.V. Fordham, C.A. Simpfendorfer, and J.A. Musick (2005). Sharks, Rays and Chimaeras: The Status of the Chondrichthyan Fishes. International Union for Conservation of Nature and Natural Resources. pp. 306–30

3 - Lessa, R., F.M. Santana, V. Batista and Z. Almeida (2000). "Age and growth of the daggernose shark, Isogomphodon oxyrhynchus, from northern Brazil". Marine and Freshwater Research 51 (4): 339–347.

4 - http://www.iucnredlist.org/

Picture References

1 - http://38.media.tumblr.com/tumblr_m8tdayXqT41qc6j5yo1_500.jpg

2 - http://upload.wikimedia.org/wikipedia/commons/3/3f/Isogomphodon_oxyrhynchus_distmap.png

3 - http://shark-references.com/images/species/600xNxIsogomphodon_oxyrhynchus,28MUELLER,aHENLE,,1838,29.jpg.pagespeed.ic.ptL484NyS4.jpg

4 - http://upload.wikimedia.org/wikipedia/commons/0/07/Rhinobatos_Rhinobatos.jpg

Thanks for reading guys; I hope you enjoyed the exploration into the daunting future of the Daggernose Shark. For the next few weeks we have requests from @laflux, @scorpion2501 and @darthaznable, but as usual drop off some comments and check out past issues in Impurest’s Bestiary.