Allis shad

Where they come from

Allis shad are big European herrings that spend most of their lives in the sea and run up rivers to spawn in spring. You see them along the Atlantic coasts from the Bay of Biscay up into the Channel and North Sea, plus parts of the Mediterranean. Think open water, big tides, cold, and lots of current.

Setting up their tank

These fish are built to cruise. Straight up: they are not a home-aquarium species. If you are in a research or public-aquarium setting and legally allowed to keep them, plan a huge, round or racetrack tank with clean, fast water and very high oxygen. Sharp corners and cluttered rockwork just lead to forehead scrapes and lost scales.

• Tank size: 10,000 L minimum for a small school, 20,000+ L is far better. Circular or long oval raceway.
• Salinity: 30-35 ppt (natural seawater). They handle brackish, but keep marine unless you are doing a controlled salinity program.
• Temperature: 10-16 C. Try hard not to let it sit above 18 C for long.
• pH: 7.9-8.3, alkalinity 7-10 dKH.
• Flow: strong, laminar gyre. Target 10-20x turnover per hour.
• Dissolved oxygen: keep near saturation (8-10 mg/L at these temps). Run big skimmers and heavy aeration.

• Gear that has worked well for me:
• - Large external moving-bed biofilter or fluidized sand bed for huge bio-load swings.
• - Ozone-fed protein skimmer to keep water polished (ORP controlled, conservative settings).
• - Chiller sized generously; these fish hate heat spikes.
• - Diffused, dimmable lighting on slow sunrise/sunset ramps.
• - Tight, flush-fitting lids or netting - they jump, and hard.

Keep the interior open. Paint or wrap the outside of the tank a matte dark color so they are not spooked by reflections. Use rounded baffles to shape flow. Any equipment inside should be smooth-faced and guarded.

What to feed them

They are midwater plankton pickers by nature. New arrivals often only take live, moving foods. Once they settle, you can wean them onto fine particulate and small meaty items carried by the current.

• Live: enriched Artemia, copepods (Tigriopus/Calanus), small mysids.
• Frozen: enriched mysis, finely chopped krill, finely chopped marine fish flesh, Cyclops blends.
• Dry/gel: high-quality marine micro-pellets or gels broadcasted into the flow once they are eating well.

Feed small portions many times a day. They have little interest in hunting the bottom, so let the current bring food past their noses. A peristaltic doser that drips a slurry into the gyre works great. Rinse frozen foods and enrich with HUFA vitamins.

How they behave and who they get along with

Shad are constant movers and feel safer in a school. Lone fish pinball off the walls. Keep them in a group of 6+ if you have the volume. They are peaceful, but they spook at pushy or very active predators.

• Best kept species-only, or with other fast, non-nippy pelagic fish that like cool water (think juvenile mullet).
• Avoid: tunas/bonitos, jacks, mackerels, barracuda, large basses, anything that chases shiny fish.
• Also avoid slow, delicate species that will be stressed by the flow.

Breeding tips

Captive breeding of Allis shad is, frankly, not a home or even typical public-aquarium project. They are anadromous and cue off seasonal changes, long migrations, shifting salinity, photoperiod, and temperature. I have not seen a verified full captive cycle. If your team is attempting research breeding under permits, here is what has been associated with spawning runs in the wild and in related clupeids.

• Gradual photoperiod increase into spring, paired with a temperature rise from winter lows around 8-10 C up to 14-18 C.
• Transition from marine to near-freshwater over days to weeks in a very long raceway with strong current.
• Large, synchronized adult school with minimal disturbance and low, diffuse lighting.
• Eggs are broadcast in flow; plan gentle egg collection screens in the current path and immediate transfer to separate hatching systems.

Common problems to watch for

• Crash injuries: nose and flank abrasions from startle runs. Fix the cause (reflections, light shocks), pad impact zones, and maintain impeccable water to prevent infection.
• Low oxygen stress: rapid gilling, gulping at the surface. Increase aeration, flow, and double-check skimmer and gas exchange.
• Ammonia spikes: these fish eat often. Use oversized biofiltration and constant monitoring; keep total ammonia at 0 and nitrite at 0.
• Parasites: marine ich/velvet can hit schooling clupeids hard. They are sensitive to copper; if treatment is needed, use carefully verified concentrations or alternative protocols under vet guidance, and treat in a separate system.
• Gas bubble disease: avoid supersaturation from leaky venturis or deep returns. Watch for bubbles in fins/eyes and correct plumbing/degassing.
• Heat stress: anything above 18-20 C for extended periods leads to poor feeding and frantic behavior. Size your chiller generously.