Protecting our fish stocks – Sea Mullet

This article was published on 15th May 2017 entitled COMMENT: Sea mullet are disappearing and something needs to be done. By Dr Myfanwy Webb at fishingworld.com.au 

(To read a post about a Great White Shark Encounter, read Story 1 EATEN ALIVE – A series of memoir stories about My Encounters with Wild Animals.)

My article caused a stir in the commercial fishing realm as expected. It is quite possible and I am optimistic that the south coast of NSW may have much higher sea mullet populations than those north of Broken Bay as mullet netting is banned within the estuaries on the south coast but still allowed in Broken Bay and other estuaries further north.

A BLACK SEA ON A CLOUDLESS DAY by Dr Myfanwy Webb

As a child I remember staring mesmerized at the inky black ocean darkened by the shadow of a cloud only it couldn’t be because the sky shone bright blue from yellow sunshine with no cloud in sight.  The dark water would shudder as breaching shoals of spawning Sea Mullet curled around and around each other endlessly. I felt the immensity of nature as I witnessed is significant natural event. As a kid I idly assumed this would continue forever. How wrong I was.

Are we losing our Sea Mullet? What happens if we do lose these fish? How important is the Sea Mullet to the ecosystem and our fisheries? These are the questions I have after seeing smaller and smaller Sea Mullet schools every year during the seasonal mullet run.  As a kid growing up in the 1970s and 80s I witnessed acres of mullet cloaking my local beach in April and May as the fish slowly made their spawning run out of Broken Bay and along the Central Coast of New South Wales. Over the years these once enormous schools have shrunk. Yet the fishing effort of the mullet fishers hasn’t shrunk. The spawning aggregations are only a few meters across now and I see less of them. I love fishing, I love the natural world and as a scientist I’m keen for some answers to my questions. So I did a bit of research and found the unexpected.

Surprisingly, Sea Mullet (Mugil cephalus) comprise the very largest catch by weight of all the fish species caught by commercial fisheries in NSW.

Sea Mullet make up 40% of the NSW Department of Primary Industry’s category of Estuary General Fishery “landings by weight”. Between 3500 and up to 5000 tonnes of Sea Mullet caught by commercial fishers each year provide bait to other commercial fishers. Caught to provide bait? That’s another surprise. We all know how much bait is not converted into fish with more loss than gain during a normal fishing session. If so much bait is wasted without good margins of return when fishing recreationally I expect it might be exponentially worse from commercial fishers because their scale of enterprise is so much larger. If that’s the case, that means it’s the Sea Mullet that is the perfectly good fish that the fisheries are throwing away. Beside bait, the mullet are targeted for another market, the roe. Roughly half the Sea Mullet are caught by beach hauling, and half by targeted ocean hauling. Not surprisingly, only a tiny proportion of the mullet captured are caught by recreational fishers. Historical data published in the Status of Fisheries Resources in NSW, 2008/09 show an overall steady increase in tonnes of Sea Mullet caught from around 2000 tonnes in 1944 – 1945 to 4000 tonnes in 2008 to 4500 tonnes presently. Now remember, this does not necessarily reflect the population size available over time. It just means more fish are caught over time. More fish caught comes with better technology and methods.

Sea Mullet are relatively fast growing reaching 45 cm in about four years, eating algae, diatoms, sea lettuce while in estuaries and are low down on the trophic pyramid. The most limiting factor (defined as the environmental factor that is of predominant importance in restricting the size of a population) of an entire food chain is the erosion of the pyramid base. The pyramid base is the largest base by volume. Erosion of the base level means less fish at the next trophic level above and consequences of that is less food available to the level above that and so on.

The caviar market sustains the mullet fishery. The reproductive eggs or roe is exported as fake caviar at $30 per kilo to America, and France, the Middle East, Japan and South East Asia. So any fish not used for their roe are the ones sold as bait. (See photos of Sea Mullet transported from the boat to vehicle in open unrefrigerated cages). The roe is the mass of small eggs in the female fish. This is the reproductive gold of the species and its literal lifeline. The fish are captured when they are chock full of eggs and spawning. They are easily netted when they are in tight spawning schools as they are concentrated in discrete slow moving balls close to shore. Out of spawning season, mullet school and behave like ordinary fish. They don’t swim in tight masses but are more spaced out, are more vigilant to predation and thus harder to catch (See Photo 1). The problem here is that when the fish are in their reproductive phase they are in a behavioural state that makes them vulnerable to predation by larger fish, seals and dolphins but more dramatically, they are sitting ducks for the licensed fish netters who can position nets around whole fish balls dragging the lot to shore.

The conflict here is the tight ball fish mating behavior puts Sea Mullet at a survival disadvantage from human predation but the mullet’s reproductive state of spawning is a fundamental natural process required to perpetuate the existence of the species.

Spawning is a crucial window of time and happens once a year for several weeks. Spawning fish are like an orgy of cows and bulls let loose together in a paddock. Without cows in season and bulls present there will be no calves in the spring. During the spawning process, female mullet are fertilized. These are the pregnant cows. To slaughter the pregnant cow, you lose not only the means to make another cow but you also lose the calf due next season. To take the mating male and female Sea Mullet out of the system, you are removing the necessary breeding adults required to produce the next year’s generation of fish. This species of fish cannot be farmed artificially and its presence on this planet completely relies on natural processes. Most fisheries do not exploit the reproductive and behavioural state of the target fish like the licensed Sea Mullet fisheries, but some that do have had decimated the stocks such as the Coral Trout fisheries in Queensland targeting pregnant fish. In fact other wild caught animals are protected during the crucial reproductive season. Think duck season. Hunting some species of native duck and quail is allowed between March and June in some states of Australia. Their breeding seasons are late winter to early spring so the hunting is permitted at a time outside of their reproductive window thus protecting the reproductive process and hence the continuation of the species. This year, the South Australian Department of Environment, Water and Natural Resources has reduced the hunting pressures of some species of ducks due to poor environmental conditions last year in 2015. The Sea Mullet also experienced poor conditions in 2015 with much of the east coast under heavy rainfall and flood during the mullet run northwards along the coast.  It is thought these estuarine flood waters pushed the Sea Mullet further out to sea than usual causing them to strenuously swim against ocean currents during their migration resulting in low body mass and less reproductive roe. Without the Sea Mullet the trophic levels above are directly influenced as there is less food to keep them alive. No one can really predict accurately how badly our ecosystem needs the Sea Mullet for its sustainability but I don’t believe it is worth the risk of us finding out the hard way. The sardine crash of 90% in the US has been blamed for starving sea lions and pelicans. The marine inhabitants are all connected to each other at some level.

Beach netting targeting Sea Mullet also results in many tonnes of by-catch caught up in the hauling nets. This is another element of the practice that is detrimental to our fisheries. Undersized bream, jew fish, whiting, tailor, flathead and other marine organisms are caught and die for no gain to anyone but the seagulls. Mullet to be kept for bait left for hours on the beach I doubt would make good bait. There has been uproar in the past about decaying fish during the mullet run (Beach mullet haul angers locals, Fishingworld.com.au 2015).

If the Department Primary Industries changed the Exploitation status of the Sea Mullet from “Fully Fished” to “No Take” at least via beach hauling net during spawning then everyone but the licensed mullet beach netters and those involved in roe export would benefit. Of course this would be a significant blow to the hardworking beach netters who I would expect adore their outdoor lifestyle and love fishing but there won’t be any jobs for fishermen and women if the numbers dwindle to the point where there are no fish (Sea Mullet or species up the tropic levels) left to net, trawl or catch by line. Maybe the commercial bait usage at the other end could be more innovative and efficiently managed somehow so less mullet fish are required for conversion into ‘better’ fish or mud crabs.

Are we losing our Sea Mullet? Fisheries are limited in options for ways to estimate fish population sizes. They like to use commercial catch rate as an indicator of stock status. They also explain that data collection of fishers is highly inaccurate and inconsistent. Catch is only what is caught. It doesn’t tell us anything about what is left.

The catch rate data from New South Wales Fisheries suggests an overall steady state of Sea Mullet caught. My problem with this is that although their catch rate data doesn’t show a steady decrease in volume, the bait balls of spawning Sea Mullet I have witnessed over the years are definitely massively smaller in volume than they were a decade or so ago. If commercial catch data is incorrect then it should not be relied upon as a measure of stock status. Inaccurate data should not be relied upon to base management decisions on and this could well be risking the health of our marine ecosystem.

On May 8^th 2016, the Daily Telegraph published an article on the Mullet Run. Keely McDonough reports, “Greg Tarrant and his son Lee, from Nelson Bay on the mid-north coast, have their own fish hauling business and are veterans of “the run”. Mr Tarrant, 48, said he has been ­involved for 33 years and his family is currently based at Stockton beach in Newcastle. “In six weeks we have caught 200 tonne of mullet and in one day we could catch 65 tonne. We are hoping for another 200 before the season is over,” the father-of-two said.”

This is our fish stocks, as much as can possibly be caught during the weeks of the mullet run, hauled in up and down the coast to be sold for fake roe export and bait. What is caught is not what is left. What is caught is what is taken out of the system. If this makes up most of the tonnage of fish caught from the sea, imagine what would happen to the densities of all the other fish types especially those in the above trophic layers if all the Sea Mullet were left out there for all the fish to grow from.

The official status of the Sea Mullet around the world could be misleading.

According to the IUCN Red List (International Union for Conservation of Nature and Natural Resources) the worldwide conservation status for Mugil cephalus is “Least Concern” (Kottelat, M. & Freyhof, J. 2012). However, it has been suggested that these lists are prone to misuse by governments and other groups that draw possibly inappropriate conclusions on the state of the environment or to effect exploitation of natural resources (Possingham et al 2002).

The good news.

Fish stocks prior to colonization were far from being consistently abundant. At the time of colonization, both indigenous and colonials found their fish catches to be highly unpredictable and unreliable. Bad practices of taking undersized fish in very large numbers via nets, seems to be the cause of a dramatic drop in fish population sizes during the first 100 years of colonization. Sea Mullet are vulnerable because of multiple reasons; low base line population most likely below full potential since at least 1880, reproductive roe targeted during acute balling up spawning phase, dominant role in commercial bait market, susceptibility to low body condition and death during extreme weather events which may increase in intensity if climate changes escalate, no significant changes in commercial fisheries management of the Sea Mullet in NSW and QLD. The significance here is if the population is in trouble and is not heading in the direction of potential numbers seen prior to colonization then the whole marine ecosystem is at risk. The good thing is with changes from fisheries, and in an ideal world with a no take at all on Sea Mullet commercially, it might be possible to witness maximum potential densities as high as they were prior to colonization not just densities a bit better than after the diminished 1880s levels. That would provide a huge platform base for the marine trophic levels above and the flow on effects should be huge.

The bad news

NSW Department of Primary Industries insists the Sea Mullet populations are sustainable and are presumably not planning to implement any management or conservation strategies.

I still favour my personal methodology to measure fish densities of Sea Mullet rather than what fisheries currently use. My measure will continue to be what I can see when I look seawards from my favourite local beaches around the months of April and May. I am hoping that one day I will again become lost and mesmerized at the sight of a black sea on a cloudless day.

***  ******* ***

References

Fairholme, J.K.E., (1856) The Blacks of Moreton Bay and the Porpoises, Proceedings of the Zoological Society of London, 11 November, p. 354,

Fishing World (2015) Beach mullet haul angers locals. Fishingworld.com.au. April.

Kottelat, M. & Freyhof, J. (2012) Mugil cephalus The IUCN Red List of Threatened Species. http://dx.doi.org/10.2305/IUCN.UK.2012.RLTS.T135567A515308.en. Downloaded on 29 June 2016.

McConough, K. (2016). Mullet run: Fishing crews cash in as hundreds of tonnes of fish is hauled in along the coast. The Sunday Telegraph. May 8^th

Possingham, H.P. et al (2002). Limits to the use of threatened species lists. Trends in Ecology & Evolution 17 (11): 503–507.

Walters, I. (1992) Seasonality of Fishing in South-east Queensland, in Queensland Archaeological Reports, vol.9, 29-34 Thomas Welsby, Sport and pastime in Moreton Bay (1931).