When fishing in water deeper than 20 metres some species of fish suffer from barotrauma when reeled to the surface. Barotrauma is where a fish can’t adapt to the change in water pressure quickly enough and the gas in their swim bladder expands as they are brought to the surface on a fisher’s line. Some species like kahawai and kingfish are more adaptable and are less susceptible to barotrauma. Snapper, unfortunately, are not a species that are as adaptable and are more likely to suffer the effects of barotrauma.

This condition has been studied and several attempts to help fish survive have been trialled and developed. One commercial product developed in the USA is called the ‘SeaQualizer’ and is like a pair of jaws that fixes to your line and then to the fish’s jaw ($60 USD). The fish is lowered on your line and when the fish hits the approximate depth set, the jaws release and the fish swims away.

A similar descender rig that involves a hook and heavy (16-20oz) weight has been commercially produced in Australia and had good success at being able to provide a viable option to return fish back to the depth they were hooked. A barbless hook is attached to a heavy sinker and then a loop is attached to the bend in the hook. A fishing line is attached to the loop so the rig can descend to the seafloor, carrying the fish which has been hooked through the top lip. A sharp tug on the line pulls the hook out of the fish’s top lip and it swims free.

The other style of descender rig developed by Kiwi marine scientist John Holdsworth has the same basic set at an affordable price. Instead of a barbless hook, it incorporates a pair of Fish Grips. Fish Grips are a pair of plastic vice grips that are attached to the top or lower lip. A hole can be drilled in the grip’s top handle so that the line can be attached to it. Another short (40cm) section of mono is attached to the lower handle and then the heavy weight. When returning a fish back to the depth it came from the grips are fastened to the fish’s jaw and both are carefully placed in the water. Gently ease the line out so the weight can carry the fish down to the depths. Once on the bottom, a sharp jerk on the line will release the grip so the fish can swim free.

Having a dedicated rod set up beforehand is a good idea as the length of time it takes to return the fish can make a big difference to its survival.

As we realise how finite and delicate our ocean resources are we need to be continually assessing better ways to fish. While this process might feel awkward at first, over time you will become well-practised at releasing fish in good condition.

We need to protect and conserve what we have. If you catch fish in water over 10m there is the likely that fish will suffer some effects of barotrauma. LegaSea encourages you to have a go at using the descender rig to reduce your impact on the marine environment.

Snapper are serial spawners and their reproductive strategy is to mass-produce their eggs and broadcast them over a wide area in the hope that a few of their offspring will survive. This is one of nature’s clever approaches to survival of a species. In the case of snapper, it works, because there is a high rate of mortality for the baby ones (like in the larvae stage) that don’t make it.

What are the odds of surviving? Well not too different to winning the lotto. That kind of puts things in perspective when it comes to looking after the undersized fish that we release. We need to first respect that those little goldfish were pretty lucky, until they ended up on our hook.

If the chances of dying are so high, how do we increase their chances of survival?

Using lures when fishing will catch fewer small snapper and lip hook them more often which gives them a better chance of living when released. Filing or crushing down the barb will make it easy to remove the fish from the hook. It can be quite harmful for the fish to be firmly squeezed as a large-handed fisher tries to rip a hook out of its jaw because the barb keeps catching on its skin.

Steady pressure on the fish when pulling it to the boat (or shore) will mean barbless hooks will still catch as many as those with a barb. In fact, there may be an argument that barbless hooks have more success because it is easier to penetrate the fish’s mouth because the barb is absent.

If you can release a fish whilst it is still in the water, even better. If it is a stroppy little fighter and you foresee a few spines in the finger as it struggles for freedom, holding it in a rubber mesh net and using a pair of pliers is the safest approach for both fish and fisher.

A word of warning – please don’t use a dry or wet cloth when holding fish prior to release. The fabric can remove the precious mucus from the fish and make it susceptible to infection on release. The mucus helps provide a barrier for disease and if this is removed by rubbing or if scales are lost because of flapping around and banging against the boat, it can be the end of the fish.

It has been popular practice to use a cloth, but it isn’t best practice so please instead try the above first – remove your barbs so releasing the fish in the water is easy, use a rubber net to contain stroppy fish and as a last resort use wet hands to handle fish. You can use the cloth on your hands afterwards, but please don’t use it on the fish. Summertime can be the time of lots of baby snapper make a nuisance of themselves but remember those were the very lucky ones, ensuring their survival can only do good for our fishery.

Selective breeding in fish – written by Anna Blair

According to Darwin’s theory of evolution, the most successful organisms will survive to thrive and pass their genes on to the next generation. While environmental factors are normally the major determinant of reproductive success, when we interfere with natural selection, the gene pool is altered, a process termed Human Induced Evolution.

Selective agents

We tend to act as selective agents when fishing because there is a natural tendency to think that ‘bigger is better’ and to place a high value on ‘PB’s’ for different species. Large trophy fish often end up on the scales – most fishing contests bear witness to that observation.

Removing a disproportionate number of fish with certain genes from a population means those genes are not passed on in the same proportion to future generations and the percentage of those fish in the total population will decline.

Size-selective harvesting or killing of larger fish means a shift to greater proportions of smaller fish in the population. These smaller sized fish pass on their genes, so the average size in the population is shifted towards the smaller end of the scale.

Fisheries-induced evolution has been happening for decades and it happens much faster than natural evolution. Archaeological evidence confirms that the average size of snapper was once much larger than it is today. The age, size and weight of snapper at maturity has declined over time with the most likely causes an increase in fishing pressure and advances in technology.

Shrinking populations

Fisheries-induced evolution poses a threat to the future state of fisheries, affecting yields, stock stability and recovery potential of populations. Size-selective harvesting may cause fish populations to reach maturity at a younger age and smaller size, at which the individuals have lower productivity.

Large female fish produce more eggs and larger males produce more sperm, so the number of offspring per head of population tends to be larger than with populations containing smaller sized fish. Larger males also tend to be preferred by females and have more reproductive success than smaller male fish.

Genetic diversity is critical for the health and success of a population because it is the raw material for evolution. Genetic traits are naturally selected for or against, based on fluctuations in environmental conditions. A reduction in genetic diversity results in decreased ability of individuals to adapt to changing conditions: fewer individuals will survive in the event of environmental change and population size decreases. The fish that do survive to produce offspring pass on similar genes, contributing to greater genetic uniformity.

The cycle repeats, making it more difficult for a species to return to the productivity and diversity it once enjoyed.

Not only does fisheries-induced evolution have a negative effect on the fish populations themselves, but it also has social and economic implications, such as decreased commercial fishing potential and a reduction in the contribution of recreational fishing to New Zealand’s economy.

Norway’s cod

An example of fisheries-induced evolution has been exhibited in the case of the Norwegian cod stock. Large fish are prized in Norway and fetch higher prices at fish markets. The cod stock has undergone multiple declines since the first quota was introduced in 1978, and since 1930 the average size and age of sexual maturity in cod has decreased significantly.

Doctoral research fellow Anne Maria Eikeset of the Centre for Ecological and Evolutionary Synthesis published findings that suggested evolutionary change, as a result of the boom in the commercial fishing industry, is the culprit. As large fish go for the highest price, their genes for large size, increased reproductive success and later sexual maturity have continuously been removed from the population.

The fact that changes are being made at the genetic level means fishing, both recreationally and commercially, is affecting species more than we have been aware of. While some populations may be able to recover in terms of biomass, it is unclear whether reversals in terms of genetic diversity are possible.

Research models produced by various groups indicate that several years of evolutionary recovery will be required to restore populations to their highly productive and diverse states for each subsequent year of exploitation at its current rate. This ‘Darwinian debt’ will need to be repaid by future generations that are already suffering from other effects of environmental neglect.

Fish for the future

So, what can we do about it? Fortunately, there are a few ways we can aid the recovery of our great New Zealand fish populations and reduce the amount of genetic diversity lost through fishing. We already have a size limit on the lower end of the scale, so maybe an upper size limit could be introduced during breeding seasons to allow big fish to reproduce and pass on their genes.

Releasing large fish will also be important and fortunately a change of attitude around killing the big ones is starting to filter through to most anglers.

Competitions should focus on sustainability rather than kill and weigh. Again, there’s a real shift to using measurement as the criteria for angling achievement. Today’s technology makes it easy to photograph a fish on a measure and have that recognised, but also allows big fish to be released to breed.

The DB Export NZ Fishing Competition is a good example of the use of technology to empower anglers to make their own decisions on what’s best for the fishery and sustainability.

We have an opportunity to make a positive change for future generations – letting some of those big catches go is worthwhile for the benefit of the future keen anglers of New Zealand.

So, when you tick off that bucket-list goal of a 20lb snapper or a 30kg kingfish, if it’s in good condition, maybe it can go back to keep those large-growth genes in the pool!

Anna Blair is studying genetics at Otago University.

This article is the property of NZ Fishing News and has been reproduced with their kind permission.

For more fishing related information, check out the NZ Fishing News website to subscribe for thier print or digital publications: NZ Fishing News

This article is the property of NZ Fishing News and has been reproduced with their kind permission. Written by Bruce Hartill from NIWA, this article gives excellent information on the effects of barotrauma and how fishers can minimise harm to any fish suffering from the change in pressure when retreived from depths greater than 20 meters.

For more fishing related information, check out the NZ Fishing News website to subscribe for thier print or digital publications: NZ Fishing News

FishCare poll on recreational fishing habits at snapper spawning time

Thank you to all who took part in the LegaSea poll on fisher’s habits at snapper spawning time. We had a good response with lots of enthusiastic comments on the post as well. It’s easy to see that snapper are a favourite amongst fishers.

Snapper conservation is an important topic. While there are legal bag limits and size restrictions in place for recreational fishers, there are also a range of voluntary and cultural practices that individuals employ to play their part in helping conserve snapper stocks. Some individuals will release any healthy, large snapper and some will limit their kill and not kill their limit.

One area of snapper conservation that is often discussed and debated are fishing practices at spawning time. LegaSea’s informal poll was produced to see if and how you and other fishers changed their practices at spawning time.

Facebook Poll Results

25%  said they change how they fish and were asked in what way

13.5 % said they didn’t change their fishing practices

43.8 % said they practice the same conservation principles all year round

17.7% said ‘Other’ and offered an explanation

With only 13% saying they didn’t change anything, the other 87% indicated they practiced some kind of snapper conservation, whether it was in spawning season, not in spawning season or other. It is heartening to see such strong awareness and willingness amongst fishers to play a part in helping conserve snapper stocks.

Our poll generated a lot of commentary around the value of a closed season at spawning time, with some supporting blanket restrictions across the board on taking snapper at this time of year.

While LegaSea applauds the courage to do something brave in the name of snapper conservation, such a restriction would require some solid evidence that a closure would increase spawning success and not just reduce access to the fishery when snapper are easiest to catch. Snapper spawning seasons vary, but can run from October to February. Apart from recreational fishers, it would have a serious economic effect on charter operators who depend on snapper for their business and many other operators in the recreational fishing industry.

Many questions arise around this topic and all have merit, for example:

1. Would a snapper seasonal closure policy yield the desired conservation results and justify the resource to police and enforce?
2. Would people still fish for other species and have to release all snapper, regardless of their condition?
3. Would other practices such as slot rules, lower seasonal bag limits, or a widespread education programme on conservation techniques do more to rebuild stocks for the resource expended?

Individuals following their convictions on conservation shows a love and care for the fishery. Passionate fishers holding a conviction or position is understandable, but before insisting that all fishers follow the same practice there needs to be proof that it is an appropriate way for all of us to behave – whether it is by law or part of our fishing culture. LegaSea has drafted a document on the snapper spawning issue as the practices we promote need to be guided by research.

We will be posting our position soon on social media, if you wish to read it now, here is the link: https://fishcare.co.nz/why-do-we-fish-in-spawning-season/

You can view the original poll/post on Facebook here – https://bit.ly/2OBpEMI

We welcome your feedback and any research that can contribute to this conversation. fishcare@legasea.co.nz.