Larval Fish

Chapter 9 in Fisheries Techniques

Chapter 9 Moyle/Cech

Larval Fish

Aka ichthyoplankton

Importance of ELS

Critical life stage

– Recruitment is difficult to predict

The recruitment problem

Implications for N

Importance

Only 20% of freshwater and 10% of

marine eggs or larvae described

Impact assessments

Collection Techniques and

ConsiderationsGears

– Advantages

– Disadvantages

– Habitats

– Gear bias

– Gear expense

– Effectiveness

Collection Techniques and

ConsiderationsActive:

– plankton nets, trawls, sleds, electrofishing

Passive:

– drift nets, emergence traps, activity traps, light

traps

Sampling considerations

What is your research question?

Spatial and temporal effects

Stats

Experimental design

Sample preservation

Formaldehyde

– 5 – 10% to fix

– 3 – 5% (buffered) to preserve

EtOH

– Long term, but shrinks larvae

Freezing

ID

Difficult

Regional guides

How to ID

Eliminate what it can’t be

Then use morphological and meristics

Temp and spawning habitat

Spawning Temp

Spawning habitat

Steps to identifying larvae

Date and water temp

Gut length

Oil globule

Gas bladder

Gut length

Determining gut length

50% gut length

90% gut length

70-75% gut length

40% gut length

Oil globule

Oil Globule present, anterior location

Oil Globule present, posterior location

Oil Globule

Oil Globule

Air bladder

No air bladder present

Air bladder present

Air Bladder

Further identification

Requires counts of myomeres- Total #, # Pre-anal, # Post-anal

Myomere

Pre-anal myomeres

Post-anal myomeres

Will allow for identification to species level

- Requires special microscopes and light sources

Other techniques

Analytical (numerical) and graphical analysis

of shape (PCA)

Cyprinidae

Gut 66% of total body length

Air bladder becoming present in post yolk

sac larvae

Pimphales spp have elliptical eyes

Nocomis spp have round eyes

Catostomidae

Gut 70-80% of total body length

Air bladder present

Long yolk sac

Centrachidae

Gut 40-45% TL

Posterior oil globule

Distinct air bladder

Clupeidae

Gut 90% TL

Sciaenidae

Gut 30-40% TL

Large posterior oil globule

Low myomere count (about 25 total)

Large deep head

Monotypic

Atherinidae

Gut 25% TL

Very slender and elongate

Monotypic

Percidae

End of gut 50% of total body length

Round eyes

Some species (e.g., log perch could have

gut length 55% of total length)

Anterior oil globule

No air bladder

Fundulidae

Nomenclature