Fish Ecology protocol

Aims of the Fish Ecology protocol are to:
­ determine the species spatial distribution (total abundances and biomass) according to
environmental factors to develop habitat modelling, community studies and ecosystem
modelling
­ to gather individual measurements for studying sex and populations differences
­ to collect specimens for identification combining molecular and morphology techniques.
1. Ichthyoplankton
All the larval stages
Specific work needs to be done on Pleuragramma antarcticum for studying their survival
conditions.
a. Early life stages
The larval stages are according to Koubbi et al. (1990).
Eggs / Embryo: spawning to hatching
Stage 1: yolk­sac larvae, hatching to complete absorption of yolk sac.
Stage 2: preflexion larvae: complete yolk sac absorption to start of
notochord flexion.
Stage 3: flexion larvae: start of notochord flexion to completion of
notochord flexion.
Stage 4: transition larvae: completion of notochord flexion to start of
metamorphosis (postflexion done). All fin rays started to formed.
Juvenile: completion of fin ray development and start of squamation to
attainment of sexual maturity
b. Pleuragramma antarcticum
i. Morphometrics, diet contents
30 specimens per net in 5% buffered seawater.
ii. Bar­coding
70% alcohol for bar­coding identification (at least 10 specimens per
developmental stages per species).
iii. Histology
15 specimens per net in bouin­holland.
iv. Biochemistry
All the remaining specimens in liquid nitrogen or –80°C.
c. Other species
For the other species, specimens will be preserved:
§ in 5% buffered seawater formalin for morphology, identification and diet
content studies,
§ in 70% alcohol for bar­coding identification (at least 10 specimens per
developmental stages per species). Pigments and morphologic description has
to be done immediately after preservation following the larval base database
(Table I). Drawing and Pictures are necessary for each stage. Description of
morphology and pigments are according to Russell (1976) or can be found in
the Ichthyoplankton information system of Alaska Fisheries science center
http://access.afsc.noaa.gov/ichthyo/use.cfm .
2. Adult fish
a. Total biomass and abundances
Total biomass and abundance of each species for each net needs to be done after each
sample.
30 individuals minimum per net per species will be used for morphometry,
determination of the reproductive stage and eventually otoliths and diet contents.
These specimens has to be numbered individually.
b. Morphometrics
Total length (TL), Standard length (SL) and Total weight (TW) needs to be
collected for a minimum of 30 specimens per species and net.
3
Figure 1: Morphometrics (from CCAMLR). Standard body length measurements of
fish: TL ­ Total Length is from the most anterior part of the snout to the most posterior
part of the caudal fin when this fin is extended along the length of the body; SL ­
Standard Length is from the most anterior part of the snout to the end of the vertebral
column (usually marked by a vertical groove in the caudal peduncle when it is flexed).
Each specimen has to be labelled and a picture taken (head on the left, mouth closed,
all fins deployed) with a vertical and horizontal scale. Morphometrics will be used to
compare populations or doing ecomorphological studies using Truss network or Thin
Plate Spline analysis. The specimens used for bar­coding or population genetics
should be photographed the same way.
These morphometric techniques are based upon taking co­ordinates of homologous
points (points that you can easily recognise on each fish) such as beginning or end of
fins, position of the eye, operculum, mouth,...(figure 2).
Figure 2 : exemple of truss network and definition of homologous points for a
Nototheniidae.
c. Reproduction
Maturity stage of Pleuragramma antarcticum, all Notothenioids and Electrona
antarctica needs to be done on 30 individuals per net samples.
* Macroscopic observations
Maturity stages scale is from recommandations of CCAMLR for all fishes
(Table II). 5 maturity stages are determined.
* Gonado Somatic Index
GW: gonad weight (g)
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EW: Eviscerated weight (g)
Calculation of GSI (Gonado Somatic Index)%: (GW*100)/EW
* Fecondity
Fecondity measurements has to be done on gravid females (stage 4).
Weight the gonad : GW
Weight 1/20 of the gonad. The sample has to be done in the middle of these
one. Count the eggs.
d. Diets
Diet contents should be weighted and preserved in 5% buffered seawater formaline.
Stomach repletion should be indicated
0 for empty
1 less than 25% of the volume
2 25 ­ 50%
3 50 ­ 75 %
4 75 ­ 100%
References :
Koubbi P., Duhamel G. & P.Camus, 1990. Early life stages of Notothenioidei (Pisces) from
the Kerguelen Islands. Cybium, 14(3) : 225­250.
CCAMLR: http://www.ccamlr.org/pu/e/e_pubs/om/toc.htm
Russell, F.S., 1976. The eggs and planktonic stages of British marine fishes.. Academic Press,
London, UK. 524 p.

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