What happens when conserving an Endangered species impacts a fishery worth A$1 million?

Conservation efforts in many parts of the world are often impacted by money. This is not a reference to the usual lack of funding for the average not-for-profit - although that is an important side note - but the often lucrative reasons for why a species has fallen into decline in the first place. With rhino horn worth more than gold and a bowl of shark fin soup selling for up to HK$2000 there is a price on the heads of wildlife so high that it can offer some convincing reasons to some parties against supporting conservation efforts.

Financial implications of lost business are also of concern to the fisheries industry. Whilst sustainable fishing is, of course, important to the fishing industry as it translates to continued employment, closing a fishery to protect a non-target species can lead to socio-economic conflict between conservationists and fishers if the fishery in question also contains a valuable target species.

This is what happened in 2012 with the release of a management strategy for the upper slope dogfish in Australia. One species of upper slope dogfish - Harrissons Dogfish (Centrophorus harrissoni) - is classified as Endangered in the IUCN Red List and uses Taupo seamount off New South Wales as a refuge. The management strategy released in 2012 proposed a higher level of protection for Taupo seamount which would officially close it to all fishing activity, therefore protecting this vulnerable species.

The road to this proposed closure had been a long winded process; Harrisson's Dogfish was first nominated for listing under the Environment Protection and Biodiversity Conservation Act in 2005. Taupo seamount was then sampled and subsequently identified as a refuge for Harrissons Dogfish in 2009 and subsequently the seamount was closed to commercial fishing activity under the advice of the Australian Fisheries Management Authority (AFMA) in 2010.  

The closure of the fishery in this instance caused controversy as the seamount chain in question contributes 25% of the annual total allowable catch of Blue-Eye Travally (Hyperoglyphe antarctica). This is a fishery which has a total value of A$1million and so the closure would have had a significant impact on the lives of the fishers and the Australian economy. 

In 2015 the original closure and planned upgrading of the seamount to Marine National Park status was revised (AFMA Ecological Risk management 2015) to allow commercial line fishing around Taupo seamount. Whilst this may initially seem like a step backwards, the revision was undertaken with a view that the fishery could be compartmentalised to allow fishers to maintain their catch of Blue-Eye Trevally whilst not impacting the Endangered Harrissons Dogfish.

Harrissons Dogfish is a diel vertical migrator - the shark spends daylight hours at depths of >550m and ascends at night-time to feed on micronekton. Researchers at CSIRO and Australian Museum hypothesised that the seamount could potentially be open to line fishing above 550m; this would allow fishers to catch Blue-Eye Travally during the day but should not have any impact on the Harrissons Dogfish stocks.

The researchers carried out their own fishing effort around the seamounts, deploying fishing lines both during the day and at night as well as into the Mid (280-550m) Zone and Deep (550-830m) Zone. The results showed that catches of Harrissons Dogfish were avoided when fishing for Blue-Eye Travally at depths of 280-550m during the daytime, using standard commercial power handline. Whilst surveying the area, the researchers also discovered that the range inhabited by Harrissons Dogfish was much wider than previously thought.

These results were used to inform policy makers when finalising the management plan for Harrissons Dogfish. Whilst the zoning category of the Taupo seamount was relaxed to allow commercial handline fishing activities, the zoning category of the Derwent Hunter Seamount was increased and the Queensland and Britannia seamounts were included in the Commonwealth Marine Reserves network owing to the new evidence of Harrisons Dogfish in these regions.

The declassification of Taupo seamount from Marine National Park to Habitat Protection Zone is never a step in the right direction as far as any conservationist is concerned. However strict regulations are in place: the fishery is subject to 100% monitoring and if any vessels interact with more than 3 Harrissons Dogfish they will lose their rights to fish in the region for 12 months. In addition to this the removal of Harrissons Dogfish has been entirely prohibited.

So when conservation conflicts with huge financial profit can there be a happy medium? This solution may be a way to keep everyone happy; however the truth of the matter is that the only way we will known is by ongoing monitoring and sampling in the region to see if the populations of Harrissons Dogfish truly are unaffected by the Blue-Eye Travally industry.

Shark Research: Population composition of blue sharks in the Central Atlantic

A group of researchers has examined population structure, size, abundance and migration patterns of blue sharks (Prinace glauca) in the Azores Archipelago in the Central North Atlantic.

Unlike many other shark species, blue sharks are relatively productive and may attain high abundances locally. This is reflected in the fisheries catch composition which the researchers monitored in the local area where blue sharks constituted 81.5% of the total catch in terms of number of individuals caught.  

Blue shark composition varies with sea surface temperature (SST), time of year and lunar cycle. The highest catch rate of blue sharks in the Central North Atlantic occurred during the winter months whilst the summer months yielded the lowest catch rate. This is congruent with evidence that female blue sharks migrate in the warmer months and appear off the coasts of Ireland and SW England. The highest catch abundance of blue sharks also coincided with the coolest SSTs, with the highest catch rate occurring in waters of 17.5°C and the lowest at the higher SST of 23°C. Evidence of several life stages of the blue shark in the Central North Atlantic indicates that this is an important ecological area for blue shark populations from both sides of the North Atlantic, as well as being a nursery area for blue sharks.

Owing to the over exploitation of many shark species by the fisheries industry, in depth knowledge of population structure and composition of shark species is an important tool in assessing vulnerability of each species. The blue shark is the most frequently caught pelagic shark species by the fisheries industry, with an estimated 86,000 tonnes fished per year; in recent years the swordfish fisheries have begun to target blue sharks owing to a reduction in the swordfish catch in the region.

Vandeperre, F., Aires-da-Silva, A., Santos, M., Ferreira, R., Bolten, A. B., Serrao Santos, R. and Afonso, P. (2014) Demography and ecology of blue shark (Prionace glauca) in the central North Atlantic. Fisheries Research. 153, 89-102