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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