Trawling for solutions

Hi there, welcome back to standing room only.

To reduce that Tryptophan induced coma resulting from 3 days of constant turkey intake let's dive right in with some positivity regarding our impacts on the marine environment of Hong Kong:

WWF-Hong Kong has been at the vanguard of environmental impact issues for 33 years and has been partially responsible for many of the environmental reforms across Hong Kong. Its Save Our Seas (SOS) campaign saw a focus on the protection of marine biodiversity. Perhaps the most prevalent result of the SOS campaign is the instigation of a trawling ban inside HK waters. Between 2004 and the ban's commencement on the 31st of December 2013 the SOS campaign applied concerted pressure on the Hong Kong SAR government through a program of public petitions and open letters from highly regarded members of academia (WWF-HK open letter) all aimed at raising awareness of the marine environments fragile state and providing researched evidence that changes need to be made quickly.

"The ban increases the public’s interest in and commitment to the sea. It will have a major positive impact on the whole ecosystem. Banning trawling is the best single action to help Hong Kong’s fishery on the road to recovery. It also shows that the government is beginning to listen to stakeholders other than the fishermen."

Prof. Yvonne Sadovy, Department of Ecology and Biodiversity, The University of Hong Kong (WWF-HK Save Our Seas supplement, 2011).

Prior to the trawling ban the management of fishery practices around Hong Kong was pretty minimal. Not surprising when we consider that, as noted in our initial fisheries post, after WW2 the primary focus for Hong Kong was to rebuild and enhance its fishing fleet in order to fulfil the growing demand for fresh fish in an increasingly competitive market (Cheung and Sadovy, 2005). Until relatively recently there simply wasn't a whole-hearted consideration of the sustainable nature of new fishery practices being adopted in HK and the situation manifested itself as a decrease in overall capture fisheries since the 1980s. In a broader perspective Hong Kong was suffering an exaggerated version of  the contemporary decreasing trend observed globally by Pauly et al (2002) whereby increasing fishery technology and expansion of fleet size resulted in over-exploitation of fishery resources and a major drop in the actual number of fish being caught per trip.

Cheung and Sadovys (2005) determination of  the variations of 'Total inshore landings' (total quantity of fish caught) and the  Catch Per Unit Effort (CPUE, basically how many fish were caught per trip compared to 1950 catches) in Hong Kong waters between 1950 and 1997.  

"Throughout the 1950s and 1960s, this huge increase of global fishing effort led to an increase in catches ... encouraging an entire generation of managers and politicians to believe that launching more boats would automatically lead to higher catches."

Shots-fired! Pauly's (2002) rhetoric places the blame for global over-exploitation of fishery resources squarely at the feet of the upper-echelons of power. 

The exclusion of Hong Kong waters to trawling practices is hoped to allow the local aquaculture to restore itself to its former glory. Samantha Lee, Senior Marine Conservation Officer for WWF-Hong Kong, expects marine stocks to recover by up to 30% inside of 5 years (Marine Science Today, 2013).

As well as increasing in numbers the decline in the mean-trophic value of catches, caused by the loss of larger slow growing species and highlighted in Mortons editorial (2005), is also estimated to reverse itself with a 10-20% increase over 5 years (WWF-HK 'submission to the Legislative Council', 2011: page 3).

Only time will tell if these changes can be maintained and have their desired effects, but for now I personally think that we can take this as evidence that the human race is beginning to take responsibility for its impacts and invest seriously in taking steps to lessen and hopefully reverse them.

TED Talk Time

Hi there,

Thought I'd throw a quick movie your way; 4 years ago Johan Rockström, a professor at Stockholm University and (at the time of filming) the executive director of the Stockholm Resilience Centre, gave a TED talk describing his 9 recently identified 'Planetary Boundaries'.

The boundaries represent limits on human impacts on the environment. Johan explains within these limits the earth can remain at a level that maintains our current global environmental state, whilst exceeding these limits (or possibly only a number of them) could cause an abrupt change in the global environmental state from which it is likely we could never return.

The talk immediately identifies human population growth as a primary pressure on the earth's environmental conditions and the identified planetary boundaries encompass the majority of the topics we have investigated so far. Although his talk takes a much wider global and temporal viewpoint than that of this blog, I think its a great piece of media that conveys how the issues we are investigating all contribute to a much larger problem.

Interestingly, although perhaps unsurprisingly, Johan suggests that many aspects of human impact need to be initially addressed on a smaller cultural scale which will then allow incremental improvements of our environmental impacts to combine and result in global scale changes. I think this is a valid observation; the solutions to excess nutrient pollution and fishery resource exploitation impacts I mentioned in earlier posts both appear to have their beginnings at grassroots level. Guidelines for the control of agriculturally derived water pollution, released last year by the FAO, noted that there has been ''considerable success'' (Food and Agriculture Organisation of the United Nations - Water Pollution Guidelines, page 13: 2013) in decreasing nutrient pollution through educating farmers in best practises and demonstrating financial savings through lower, correctly timed applications of fertiliser.

As yet we haven't broached the subject of 'reducing impacts' but I think this video offers us a great excuse to start looking at the more positive side of the subject in my next post.

Take care and don't stress about Christmas shopping to much.

Blooming Hell!

Hello again,

Today's post is going to be a little different and self indulgent; as a member of the Environmental Modelling MSc course at UCL I was particularly interested in a paper I referenced last week by Lai and Yin (2014). The paper investigated the potential for Algae Blooms to derive from physical accumulation via the application of a coastal circulation model.

Typically, algae blooms are considered to result from excess agricultural nutrients entering the aquatic system and promoting the growth of diatoms or other single celled algae to an exaggerated level (eutrophication). As the concentrations of algae increase they reach toxic levels (referred to as 'Harmful Algae Blooms' or HABs), ingestion of which can increase mortality rates of marine life and cause illness in those that eat the affected fish/shellfish etc. Backer and McGillicuddy's (2006) study on the relationship between humans and the ocean contains a plethora of illnesses that can be caused by ingestion, although I wouldn't advise reading it if you're at all partial to seafood!

Delicious! a glass of Microcystis bacteria (this is a surface sample of a HAB affected freshwater lake). These bacteria excrete neuro-toxins which can kill humans (Oberholster et al, 2004). Photo credited to T. Bridgeman in (Backer and McGillicuddy, 2006). Presumably Mr Bridgeman is no longer with us.

Lai and Yin's (2013) study theorised that, aside from nutrient pollution, blooms can arise from a combination of physical factors causing an accumulation of the single celled algae. Their theory was based on observations in Port Shelter bay in north-east Hong Kong; the bay suffers from frequent HAB's of Dinoflagellates that tend to occur in the same area each time (a band mirroring the coastline). Water samples from the bay indicate that nutrient levels are too low to produce a eutrophication event and hence a second, physical factor seemed likely.

In order to understand the complex mechanisms at play a Finite Volume Community Ocean Model (FVCOM) was used in combination with a series of water samples that were taken during a bloom event and identified Algae concentrations. The model was utilised in 3 experiments, each increasing in complexity by the application of new variables, with assessment of the potential for aggregation:

• Experiment 1 involved two model runs: Both utilised the morphology of the coastal region and the effects of the tidal forcing on the movement of algae in the bay. However, 1A was performed under a homogenous water profile (basically ignoring the effects of changing temperture and salinity levels based upon water depth), whilst the 1B was performed under a stratified water profile whereby the temperature and salinity (which both affect algae concentrations) were utilised to aid aggregation of the Dinoflagellates.
• Experiment 2 maintained the stratified water profile and tidal forcing but included the effects of wind conditions on the surface of the water.
• Experiment 3 enhanced Experiment 2 with the inclusion of the ability for the Dinoflagellates to swim upwards, against flow in order to promote photosynthesise. This ability results in amplified accumulation as the flagellates are suspended in the same location, swimming against the current, for longer periods of time.

The experiments proved that by applying several variables:

• An accurate approximation of the coastal topography
• Tidal forcing
• Wind effects
• A stratified, saline/temperature dependent water profile
• A potential for the modelled particles (in this case the Dinoflagellatte algae) to vertically migrate towards the surface

The FVCOM model can simulate the physical aggregation effects observed across Port Shelter bay! Woohoo! Modelled cross-sections across portions of the bay that have been observed to contain HAB's clearly indicate that there is a convergence of currents (and hence Dinoflagellates).

Cross sections of the modelled bay indicating convergence of currents. Larger arrows on the surface indicate position of observed HABs whilst smaller arrows indicate current direction (Lai and Ying, 2014. page 73).

Cartoon representation of the modelled process (Lai and Ying, 2014. page 74).

I hope this sortie into my preferred discipline has given you a little more insight into how we can begin to enhance our understanding of the environment. I feel that mitigation of human impacts on the environment must begin with a good understanding of how the environment works and how our impacts actually affect it. As we have seen in this post, natural processes can cause similar outcomes as those derived from humans. Without this further investigation we may have assumed that such HAB events are solely due to our influence, giving us a misguided sense of our impact.

As a thanks for joining me again, here's another Harmful Bloom.

Courtesy of lotr.wikia.com.

Teach a man to fish a lot!

Hi there, welcome back.

Last week we had a run through the evolution of Hong Kong's fishery practises over the last 80 years. We observed that Hong Kong's fishing fleet evolved from low tech, mostly wind powered, vessels to a predominantly mechanised fleet. This mechanisation, and the newer fishing practises that it enabled, resulted in yearly increases in fishery yields. Although these increases are associated with an actual decrease in per unit yield (basically catches are becoming smaller so an increased number of catches is require to meet the demand).

This post is going to have a quick look at three dominant fishery methods utilised by the Hong Kong fleet:

Gei Wai (fish ponds):

Gei Wai are large bunded ponds that can be either replenished tidally or through deviation of freshwater sources dependent upon the culture (Lai et al, 1999). They are effectively nurseries where young fish, shrimp etc. are introduced and allowed to mature in a relatively protected, and easily farmed habitat (www.wwf.org, 2014).

As I'm sure you've already realised, this method requires a large areas of coastal land (perpetually at a premium in Hong Kong) and as such the practise is slowly being ousted in favour or less spatially demanding methods. Gei Wai now predominately survive in the very northern portion of the new Territories (Lai et al, 1999) on government owned land.

Marine Culture Cages:

Culture cages are large, fine grated cages suspend from rafts in coastal waters. The practise was adopted in the 1960s after growing population demands required a greater output from marine resources.

Gei Wai and Fish Culture Zones in 1998, courtesy of www.afcd.gov.hk.

Although the method thrived for approximately 20 years (Morton, 2005) this flourishing new industry couldn't sustain itself for very long. Typically the farms were situated in protected environments (shallow coastal bays etc.) in order to allow the livestock to growth as quickly and easily as possible.

However, the low current energy of these protective areas prevented the excess chum and supplements that were fed to the fish from being transported away from the farm area resulting in a rising levels of local nutrient pollution.


The increasing levels of marine population deriving from Hong Kong's rising population also had a severe impact on Cage fishery. Perhaps most notable impact event is the 1998 'Red tide': a significant algae bloom swept across Hong Kong and decimated caged cultures and corals. The bloom affected 25 of the culture zones in HK and resulted in a loss of approximately 2,500 tonnes of fish culture at an estimated HK$250,000,000 impact on the Hong Kong economy (Yang et al, 2003).

Capture fisheries:

A quick referal to the ever useful 'Hong Kong: The Facts' government released fact sheet (www.gov.hk, 2014) gives us a summation of Hong Kong's modern fisheries fleet:

• 33% of vessels are >15m and carry out activities outside HK local waters, along the northern continental shelf of south china sea: Trawling, Line fishing and Gill netting.
• The remaining two thirds of the fleet comprise smaller vessels whose activities are generally carried out inside HK local waters (Gill-Netting, Line fishing, Purse Seiners and Cage Trapping).

For the sake of brevity I am going to focus on, arguably, the most impactful of these capture methods: Trawling. I feel that the other techniques, whilst clearly impacting the environment, can pretty much be regarded as a single entity that represents the exploitation of shallow marine ecology. Although many of the techniques are similar to trawling, they typically do not disturb the seabed envrionment to the same degree.

The trawling method involves dragging large nets across, or near, the seabed in order to catch fish and Crustacea.

Basic trawling method, courtesy of web.duke.edu.

The environmental impacts of trawling have long been recognised (Van Dolah et al, 1987) and consist of two primary effects:

• Huge plumes of sediment are disturbed by the nets. Similar to the side effects of reclamation the spread of the disturbed sediment can spread across huge areas preventing phytoplankton photosynthesis (Yan et al, 2013). Fish species also have 'varying tolerances of suspended solids' (Newell et al, 1998. Page 25) and may suffer clogging of the gills eventually preventing feeding and causing death.
• The second impact is a much more obvious and severe matter; the act of dragging a net (complete with ballast to maintain negative buoyancy) literally scours a path across the sea floor destroying habitats in its way. Coral reefs are particularly susceptible to this destruction due to the slow growth rate. Years of growth can be removed in a single pass (Hall-Spencer et al, 2002).

The severity of trawling impact on marine ecology is such that in early 2013 the practice was banned inside HK local waters, given Hong Kong's establishment and ubiquitous association with fishery practises the acknowledgement of trawling's destructive capability was a huge step. An article, released on the day of the bans commencement by the South China Morning Post (www.scmp.com, 2013) stated that HK$1.7 billion were due to be paid out as compensation to affected companies and fishery families.

Above is a quick Youtube clip issued by www.seafish.org. It's not an immensely exciting clip but I think it really allows you to comprehend just how much damage trawling could do across delicate marine ecologies. Scary!

Teach a man to fish

Unsurprisingly, a major reason for Hong Kong's original settlement and early expansion is due to it's exceptional marine resources. The East China Sea, South China Sea and freshwater outflow from the Pearl River provide large expanses of varied aquaculture.

The increasing population of Hong Kong and its demand for these fishery resources has resulted in their severe over-exploitation with little to no evidence of improvement. A study, commissioned by the Agriculture, Fisheries and Conservation Department of the HK government, identified that over the last 25 years catches have decreased by almost 50%. In addition 12 of 17 commercial species in HK waters have been identified as being "heavily over-exploited" whilst the remaining 5 species are "fully exploited". The study is referred to in  the Fisheries Protection (Specification of Apparatus) (Amendment) Notice (2011) by LegCo (Hong Kongs Legislative Council), although the original document seems to be elusive, if you come across it please let me know.

Perhaps its the years I spent in my previous discipline of archaeology speaking but I feel that to appreciate the current state of affairs we really need to step back a little and take a quick look at how HK reached this situation. An article by Morton (2005) describes HK fisheries evolution from larger, slow growing species that are worth more to smaller, faster growing species that are worth less. The article, whilst not referenced, touches upon some of the land marks in this evolution, with a little fleshing out we can develop clearer idea of how the HK's fleet has evolved:

• The 'Fisheries Research Unit' (FRU) was conceptualised in the late 1930's (Morton 2005), although the its official establishment appears to have occured some 20 years later (Mellor 1981, pg 198). The FRU's aim was to determine how HK's technologically inferior fishing fleet could compete with Japans relatively mechanised, larger fleet which shared portions of the same waters and targeted the same species, effectively directly competing with China and HK for marine resources.

Late 19th Century Chinese fishing 'Junk', Courtesy of hongwrong.com

• The 2nd Sino-Japanese war saw the occupation of China. During this time the Japanese possessed a monopoly on fishery resource exploitation in the East China Sea. As a result supplies of fresh fish to HK were reduced to near zero (and as we have already seen Hong Kong is heavily dependent on imports from China). HK fishery was forced to deal with an overnight increase in demand, fairly at odds with its current, at the time, methods.
• However, Japanese occupation of HK towards the end of the war sparked a technological renovation of the local fishing fleet allowing  larger catches from larger areas to be acquired (Morton 2005).
• In 1960 a refreshed governmental focus on the state of HK's fleet began. The government assumed control of, and invested in,  the FRU (Chan et al, pg 4: 1996). Representing an official governmental recognition of the potentially troubling situation. This governmental interest and investment continued steadily for around twenty years.
• After governmental intervention the catch totals of the HK fleet were noted to rise annually from 53,000 to 224,000 in 1990. However, whilst fishery totals increased year on year it is reported that the catch per capita began to steadily decline from the late 1980's onwards. These declines are noted not only in Hong Kong but worldwide. Anderson et al's (2011) studies of trends in the expansion of invertebrate fisheries reflects Mortons conclusions of a declining trend in marine catches, albeit on a global scale, noting that total catches of marine invertebrates rose from 2 million in 1950 to 12 million present day (2011). Whilst the factors governing each decline are not identical (as we may venture into next time) they both involve a core theme of increased activity and exploitation reaching a tipping point, beyond which the environment cannot cope with the strain.

Join me next time when we will take a look at the methods that Hong Kong utilised during the enhancement of its fisheries.

After reading Anderson et al's (2011) on invertebrate fishery trends I started to read up on Sea Cucumbers.... I urge you to do the same: LOOK HOW CRAZY THEY ARE!

Courtesy of NationalGeographic.com