I wonder if the Zoological Society of London (ZSL) purposely waited until their last event to bring out their maverick speaker. Like a summer special. Professor Jeppe Kolding from the University of Bergen really shook those cosy conservationists up. It started when, during the course of his talk about small-scale fisheries, he revealed he’d been a nurse before he’d become a fisheries scientist. He’d nursed in Africa and had seen people starve under his care.

He said, ’Watching people die from hunger never leaves you.’ Surely, not many zoologists could attest to that.

Not that it was busy though. The ZSL’s final event before summer was titled ‘Shifting tides: how can small-scale fisheries help address the Sustainable Development Goals’. The ex-President of the Zoological Society, Field Marshal Sir John Chapple and his wife, Annabel sat next to me. ‘Quiet tonight,’ Chapple announced, Colonel Hathi-style, ‘though I guess it doesn’t help with the title.’ He said this after he’d told me how he’d saved London Zoo from financial ruin in 1992. That bit was juicy. 

Anyhow, I’m digressing. Prof Kolding also revealed that if he had his way, he’d get rid of the regulations of fisheries as they exist today. Yep – all of it. That means catch size, net size, mesh size, type of net. See ya later fishing rules. Remember, this guy saw people starving. 

Kolding’s talk centred around preventing starvation in developing countries. For this, fisheries provide both food as well as essential micronutrients – iron, calcium and selenium. Micronutrients are needed in only relatively small amounts, but often contribute to the tragedy of ‘hidden hunger’. Hidden hunger accounts for over a million deaths a year, often in children under two-years old. Years of living and working in Africa has given Kolding this food-on-the-table insight – use the smallest fish. 

He writes, ‘Catching small fish, which are simply sun-dried and consumed whole, is the most high-yielding, eco-friendly, low CO2 emission and nourishing way of utilising aquatic resources’. 

Now I’m no fisheries expert, but I know enough about fishery conservation policy to understand this idea is radical. Everything about fishing quotas revolve around catch size. That we should take the big fish and let the little fish grow. According to Kolding, this type of fisheries management is misguided at best. This is because aquatic ecosystems are erroneously compared to land-based models. 

Fish have unique life cycles for vertebrates. They breed like plants – giving rise to enormous numbers of offspring. At the same time, they feed like lions, eating each other at almost every turn. To translate into numbers, for every kilogram of large fish, there are 6kgs of fish who have died to make one kilogram of large fish. It’s a cost-heavy system. And in modern, so-called efficient fishing quotas, we take the large fish. Why? Because until now, this has seemed the most sustainable way of fishing – known commonly as the Maximum Sustainable Yield (MSY). Take the fish at their maximum number whilst ensuring they can still reproduce sustainably.

Except for small-scale fisheries that is. Traditionally less regulated and with both eyes on catchability, small-scale fisheries take what they can – particularly in the developing world. Kolding uses Lake Kariba in Africa as a prime example of small-scale fishing practice. The largest man-made lake in the world in terms of volume of water, Lake Kariba borders two countries – Zimbabwe to the north and Zambia to the south.

On the Zimbabwean side of Lake Kariba, a regulated fishery exists. Zimbabwe monitors effort versus catch rates. Over the years, numbers of fish are reported to have slightly increased, but because of catch size requirements, only a few species of fish are being caught. 

On the Zambian side however, it’s an entirely different picture. Same lake, same fish ecology, different numbers. There is almost no regulation on this side of Lake Kariba. If you look at the species of fish caught, Zambians catch everything. The overall species rate doesn’t change because a slice is being taken out of the whole trophic level rather than just the top end of the food chain.

Now think ecosystem. If you take only one part of the trophic level, or food chain, it’s a well-known fact this can cause massive ecological change. A famous example is the North Atlantic cod fishery. Cod levels became so low from fishing pressure in the 1980s and early 90s, the fish the Atlantic cod once preyed upon are so now plentiful, they’re the ones likely preventing a return of cod stocks. There isn’t enough big cod to eat them anymore, so prey have turned predator on cod eggs and fry. Kinda sci-fi, no? This ecosystem change shows mature Atlantic cod were an essential part of the food chain – a ‘keystone species’. The whole ecosystem changed when they were fished out. 

With this in mind, how can fisheries reconcile ecosystem structure with maximum sustainable yield? Kolding has a proposal: take everything along the whole biomass slope. In this way people are fed and the essential ecosystem is preserved. Does it leave less fish overall? Kolding concluded on these two points:

1. The oceans contribute over 50% of the global biological production – but humans only collect 3% of our food from the oceans. If you take from all ends of the food chain, there should be enough to both eat and conserve. 

2. I think Kolding got a little wistful here. He reminded us his home country of Norway leads the world in terms of responsible, recorded and efficient fishing practice. And yet he pointed out in recent years, the number of Norwegian small-scale fisherman have declined by over 90%. This has left just a few businesses and people getting rich – all under the guise of efficiency. But does efficiency = fairness? 

The conservationists squirmed. Bell rang for summer.