All Things

Acipenseridae

The Devonian:

‘Age of Fishes’

• ~416 million years ago

• Massive radiation of fishes

• 2 ancient lineages (classes):- Chondrichthyes, cartilaginous fishes- Osteichthyes, superclass giving rise to

‘the bony fishes’

Class Sarcopterygii – lobe-finned fishesClass Actinopterygii – ray-finned fishes

Hybodus shark- anearlyspecies

Superclass

Osteichthyes

Actinopterygii

Class ActinopterygiiChondrostei, &

Acipenseriformes

• Notice how there is virtually no branching in the Chondrostei sub-class

• Very little diversification

An ancient sturgeon, ~70 million years BP.

Sturgeon traits• Smooth, scale-less skin • Primarily cartilaginous, some ossifications• Heteroceral tail• Rows of armoured scutes• Chemo sensory barbels (n=4)• Protractible mouth

Whitesturgeon

• Opportunistic feeder• Predator• Scavenger• Benthic feeder

• Sturgeon body form unchanged for millennia - often referred to as ‘living fossils’

• Model of body size evolution(Rabosky et al. 2012)

Beluga sturgeon(H. Huso)

~ 7 m

Dwarf sturgeon(P. hermanni)~ 25 cm

Sturgeon traits

White sturgeon

FraserRiverspawninghabitat

• Very long lived, 60+ yrs• Late age at maturity (~ 20 yrs)• Highly fecund• Intermittent spawners• = a ‘slow’ life history

• Migratory (anadromous, potamodromous)• Marine habitat use is variable • All spawn in freshwater• Can make extraordinarily long marine and/or

freshwater migrations

Sturgeon life history

• Four genera• Holarctic distribution• 25 extant species• Most critically endangered group

of species in the world

A. mikadoiH. dauricusA. schrenckiiA. sinensisA. dabryanusA. baerii

P. fedtschenkoiP. kaufmanniP. hermanniA. stellatusA. ruthenus (LC)A. nudiventrisA. persicusA. gueldenstaedtiiA. sturioA. naccariiH. huso

A. medirostris (NT)A. transmotanus (LC)

A. fuvescens (LC)S. platorynchus (V)

S. albusS. suttkusi

A. brevirostrumA. oxyrinchus (NT)

IUCN Red List- 19 of 25 species Endangered or Critically Endangered

Conservation status

Main threats:

Aral SeaCriticallyendangeredA.nudiventris

1989 20142. Habitat loss: Dams, pollution,

climate change

3. Recreational fishing? ~ $200 million /yrin BC alone

1. Over-harvest: Mostly for caviar$ $ $

Recreational fishing effects: Despite perception as relatively benign, it has many negative effects on fish survival & fitness.

White Sturgeon. Lower Fraser River –Threatened (COSEWIC)

• Huge catch & release fishery • No seasonal regulations or limits on # caught• Busiest June through September, during spawning !!• Recapture rate is ~ 70%. Some fish caught ~6x/year!• Fight times can exceed 90 minutes• Lethal/sublethal effects unknown.

Province of British ColumbiaMinistry of Forests, Lands, & Natural Resource Operations2017 Assessment report

Problems with recruitment

• Adult survival good• But recruitment of small fish

decreasing

• Spawning habitat degradation?

• Poaching of spawning adults?

• Sub-lethal impacts of fishery???

How do we assess the impact of Rec. fishing?STUDY: Reflex Action Mortality Predictors

a.k.a. “RAMP”• Assess specific reflexes after fisheries stress, e.g.

orientation, balance, breathing• Correlate with physiological stress indicators• Predict post-release recovery potential, behaviour, &

survival probability

Conservation implications• Allows fishers and guides to quickly predict how likely the fish is to survival after release

RAMP validation with white sturgeonA. transmontanus

Montana McLean, Dalhousie PhD student

Tested five reflexes after angling:

• Orientation (righting)• Tail grab• Head complex• Mouth extension• Body flex

Sum of individual scores = RAMP score

Fun on the Fraser River

Angling time (minutes)

Cort

isol (

ngm

l-1)

RAM

P sc

ore

Reco

very

tim

e (m

in)

Lact

ate

(mm

ol L-1

)

RAMP validation

Intense Angling:

• Increased RAMP score• Increased physiological stress• Increased recovery times

Seasonal Effect:

• All measures higher in summer• Fraser temps getting hot > 25 °C

RAMP validation with telemetry

Fish then released with

acoustic transmitters

Relate RAMP & physiology to subsequent behaviour:

• Seasonal movementsin river

• Ocean migration• Fall-back / death

2013-16

N=167 sturgeon tagged

Seasonal movements

Summer- lower river- forays into estuary

Winter- upper river- localized into clusters / hotspots

150

100

50

0

Large scale marine movements – acoustic

telemetry

• Adult white sturgeon tagged in Klamath River, Cali

• Summer migration to Fraser River, spends a year

• Migrates south to Sacramento River to spawn

• Total marine distance ~2500 km

• Potamodromous and anadromous migrations

Questions moving forward...Yours Truly• Lots of tracking data to analyze

• Is post-release behaviour severely altered?• How long are the recovery periods?• Do highly stressed fish move to spawning areas?• Seasonal/temperature affects?• How might the rec. fishery be better managed?