Reproductive Ecology of Fishes

1
Reproductive Ecology of Fishes

• Influence of Reproductive Strategy on
• Estimates of FECUNDITY

2
Outline

• What is Fecundity

• Why is it important

• Challenges in determining an estimate of
  fecundity

• The aid of sound production of fish in
  determining an estimate of fecundity

• Conclusion

3
Fecundity?
The number of eggs that a female spawns over a
defined time period.

• Annual

• Annual population

• Breeding season

• Batch

• lifetime

4
Importance of Fecundity to Fisheries Management

• One method of estimating abundance of large fish
  stocks

Egg production equation P BRF P total egg
production of a fish stock B Biomass of the
spawning stock R sex ration (biomass of
spawning females as a proportion of the
abundance of females and males) F Annual
FECUNDITY
5
Challenges in determining F

• Fish exhibit a wide heterogeneity in
  reproductive strategy - diverse and not
  comparable

• How to determine fecundity is different for
  different species

• Depends on three different factors

1. Spawning pattern
2. Ovarian organization
3. Fecundity type
6
Spawning Pattern

• Batch spawner

• Total spawner

• Season/s

7
Ovarian Organization

• Synchronous - all oocytes develop in unison

• Group Synchronous - two cohorts of oocytes
  that develop in unison

• Asynchronous - ovary has oocytes in multiple
  stages of development at every
  conceivable stage

8
Fecundity Type

• Indeterminate - unyolked oocytes continue to
  be matured and spawned during the
  spawning season

• Determinate - once spawning season has started
  no further oocyte development
  occurs

9

Capelin

• Synchronous
• Determinate
• Total spawners

10

• Group-synchronous
• Determinate
• Total spawners

Red Fishes
11
Atlantic Halibut
Haddock
Cod

• Group-synchronous
• Determinate
• Batch spawners

Whiting
12
Sole

• Asynchronous
• Determinate
• Batch spawners

Atlantic Mackerel
13
European Hake
Yellowfin Tuna
Anchovies

• Asynchronous
• Indeterminate
• Batch spawners

Atlantic Swordfish
Pilchard
14
Sound Production of Fish

• Increase in sound production of soniferous fish
  during spawning season

• Benefits
• 1. Species recognition
• 2. Synchronizes the spawning activity
• 3. Mate selectivity

15
Haddock
When Spawning
When Courting
Aggressive Male
Male interested
Tony Hawkins
16
Waveforms and Spectrograms
17
How does this relate to fecundity?
PASSIVE ACOUSTICS
Identify essential habitat requirements
Determine spawning grounds
Determine feeding grounds
Determine feeding time
Determine time of spawning
Map habitat
Study feeding behavior
Obtain annual fecundity estimates
Protect habitat
Enhance consumption rate studies
Better estimate the reproductive output for an
entire spawning season
Help determine status of stock
18
Conclusion

• Different fish spawn in different ways

• Important to understand and correctly identify
  a species reproductive strategies to
  accurately estimate their reproductive
  potential.

19
Lab Indices

• Gonadsomatic index (GSI)
• (gonad weight / somatic weight)100
• - gonad weight in relation to somatic weight
• - used as an index to gauge how much energy a
  fish is investing in reproduction
  at a given point in time.

• hepatosomatic index (HIS)
• (liver weight / somatic weight)100
• - liver weight in relation to somatic weight
• - used as an index to gauge the condition
  (health) of a fish

20
Lab Sexing
Developing Male
Developing Female
21
Lab Sonic Muscles