Bobtail squid photo by Bob Mehen
Being caught, placed in a bucket with other livestock and transported home is going to be very stressful for fish and other livestock. If you aren't careful some livestock may not even make it back to your aquarium alive. With a little thought and care it is very easy to minimise this stress.
Use a large container with a lot of water, this will heat up more slowly and a large volume of water will keep fresh for longer. Keep the container with livestock out of the direct sun at all times, if you stand it in a rockpool it will keep cooler than exposed on the rocks.
Don't over stock the container at the beach, you can always comeback later.
Don't mix predator and prey in the same container, even though they have just been caught, some fish won't let an easy meal slip them by.
Don't leave anything in the initial container for to long.
Double bag all the livestock so that nothing gets trapped in a corner.
Don't fill the bags with water, use enough water to keep the animal covered but the majority of the bags volume should be filled with air as this contains a lot more oxygen and will help to prevent the conditions in the bag from becoming anoxic.
Pack the bags so that they can't slosh around.
Use a separate bag for each animal.
Turn off all lighting and close the curtains to the room, the subdued lighting is less stressful when coming out of total darkness in to subdued lighting than suddenly being under bright lights.
Float the bags for a while to let the temperature equalise with the aquarium.
*Fish only, carefully open the bag using scissors and not by puncturing it with a thumb or finger. Using the puncture method momentarily increases the pressure in the bag and could cause damage to a fishes swim bladder.
Once open let the water in the aquarium and the water in the bag mix for a while. After a few minutes let the fish swim out of the bag of their own accord.
Invertebrates need more careful handling because their osmoregulatory system is less able to cope with any sudden changes. Once the bag is opened they should be placed in a container (using the original water only) and tank water allowed to drip in to the container through a small restricted siphon pipe. This allows the two waters to slowly mix without any sudden changes, after several hours the invert can be placed safely in to the aquarium.
We noticed that some fish (shannies, scorpionfish and various gobies) settled down almost immediately and began looking for food or staking out a territory. Others like mullet fry, rocklings and so on were obviously very stressed by the experience but if left in a darkened room for just a couple of hours they too settled down and began to feed. In our own experience all the fish we have encountered were fully settled after 24 hours and the aquarium lighting could be used.