Avoid suffering spawnbound carp mortalities

March 20, 2024 0 Comments

I hope we all know the dangers of letting your dog loose in a field of sheep? Even if those sheep aren’t attacked, exposing them to stress is enough for those pregnant sheep to abort their lamb. Therefore it’s particularly damaging when those sheep are in lamb because the losses are potentially double!

In the dairy industry, any stress on a cow that’s in calf (pregnant) can cause the cow to abort it’s calf which leads to the premature arrival of a very under developed carcass. There’s a scenario worse than that whereby the cow retains its aborted calf which can be fatal as the aborted calf breaks down inside the cow.

What relevance does this have to fish?! We all hear of carp mortalities that are considered ‘spawn bound’, surely we can draw some parallels to the above scenarios?

The egg mass of a large female carp can account for up to 25% of her total bodyweight on the approach to spawning.

The eggs swell and mature ready for the environmental parameters to approach perfect, at which point the annual event is triggered.

What happens if this fish is caught at this point?

Exposing a female fish to an extreme level of stress and cardiovascular strain at a point when she’s at her most vulnerable is going to have the same effect as it would with the aforementioned sheep or cow scenario, surely?

Fisheries are very good at closing at the first signs of spawning, but is that too late?

Surely the approach to spawning is similar to any other animal and the most vulnerable time for these female fish which have the job of hauling around a huge egg mass pending fertilisation from a randy male.

It’s difficult to police anglers and predict when the fish will spawn, which is why I think the responsibility is shared between management and the anglers. Anglers must understand that they should only remove fish from the water as a very last resort. Respectful of the vulnerability of these females and the stress impact the capture has had on the immune defences of that fish at a time when bacterial activity is on the increase.

Here’s how you can clear your conscience and rid yourself of guilt for fishing for these fish at their most vulnerable time of year:

Have everything ready to deal with handling your catch.
Unhook the fish in the net.
Take your shots in the water.
Return the fish as soon as possible.

There are environmental factors that contribute to this vulnerable time of year too.

Coming out of the winter, the natural defences of fish are much slower to respond to the rising water temperatures when compared to the reproductive rate of bacteria which are much faster to react. This is why bacterial infection is relatively common in the early summer until the natural defences of the fish improve at which point you hope surviving fish overcome infection. These challenges are what make or break a growing season, because a spring infection could take weeks or months to overcome, which closes that window of opportunity for summer growth.

Supplementary feeding in the winter/spring prior to spawning reduces fish stress and strengthens their natural immune responses. It also improves feeding confidence to combat the negative impact spring angling has on the growth and progression of your stock…

Why are spring captures so damaging?

Typical spring carp angling usually involves less bait, the fish usually come out of the winter slightly lethargic and their metabolism naturally isn’t quite firing on all cylinders. So fishing with small amounts of bait usually yields better results. From the fish’s point of view, having less free food and more traps can seed the cautious feeding behaviour which could influence the rest of the growing season. Imagine being that fish coming out of the winter, you come across the rare sight of food taking the appearance of a bright yellow pineapple pop-up, ‘Lovely Jubbly’ you eat it and get caught. Naturally you would associate feeding with capture and you’d become more careful, you would likely feed with more hesitation in the future. Whereas, if you’re feeding your fish throughout the winter, although you’re not seeing much material growth from the fish, they’re getting reward for feeding and build confidence in doing so. By training your fish to feed with confidence, spring captures will undoubtedly be less impactful on the rest of the growing season.

Bringing this back to the point of reducing spawn bound mortalities, there are 3 main action points to think about.

Educate anglers to limit dry fish handling, especially at this time of year.
Monitor captures and condition of fish and consider a spawning closure well in advance of the actual event.
Feed consistently throughout the winter and spring to encourage confident feeding behaviours and reduce the longer term behavioural impact of spring captures.

Having said all of that, the fish should look the best at this time of year, it’s famously the best period for angling. I’m not whistle blowing or suggesting Spring angling is immoral or unfair, we just need to be aware of the increased vulnerability of these fish and adapt our approach to minimise issues and protect the opportunity for growth in the summer.

I hope this alternative view puts the pending season inter a little more perspective, please do contact us if you have any questions.

Ben Pinniger