289
9 Studying and Monitoring Aggregating Species
9.4 Methods Described
The basic uses and limitations of methods are described below in single paragraphs.
For many topics, more detailed technical information is presented in a subsequent
section and the SCRFA study manual (Colin et al. 2003 , www.SCRFA.org ). For
some additional methods, references are provided.
AF – Artifi cial Fertilization and Gamete Collection
One of the simplest ways to obtain large numbers of fertile eggs from a spawning
aggregation is to collect individuals through diving or fi shing at the time of spawning, hand-strip and mix the gametes. Fish to be speared can sometimes be selected
by sex or size (Colin et al. 1987 ) . Running ripe males can often be obtained some
time ahead, and if maintained alive sperm can be stripped as needed. The sperm of
dead males remain viable in the testes for hours. Testes (either in the fi sh or removed)
can be chilled (but not frozen) for a day or more and the sperm remains viable
(Colin et al. 1996 ) . Eggs must generally be obtained at the time of spawning either
through collection of females ready to spawn or following hormone injections of
fi sh held in aquaria (Watanabe et al. 1995 ) . It is uncertain how long hydrated eggs
can be maintained before fertilization. Standard techniques are used to mix eggs and
sperm for fertilization, followed by fi rst cleavage within an hour or less to confi rm
development.
AM – Acoustic Monitoring
When reef fi shes spawn planktonic eggs, they may produce both hydrodynamic
sounds (noise) and species-specifi c sounds. Potentially these sounds can be monitored by an acoustic receiving system at or near the spawning site and used to
document spawning activity over time (Lobel 1992 ) .
Subject/parameter
F/D or F/I
Method
Location of gametes after release
I
DR, DY, DO
Migration pathways
DI
DO, AT
Key to FD/FI and Methods-FD/FI
D fi shery dependent, I fi shery independent, DI both , AF artifi cial fertilization and gamete collection,
AM acoustic monitoring, AT acoustic tag, BM bathymetric mapping, DO direct observation by
snorkeling or diving, DR drifter release, DY dye release and water tagging, EC egg collection, EM
experimental manipulation, FM fecundity measurements, FS fi shery sampling from fi sher catch,
GC gut contents, GD GPS density survey, GN gonad study, GS genetic sampling, HA hydroacoustic
survey, IS instrument at site, LD longterm database, OT sampling and analysis of otoliths, RV remote
operating vehicle, SC specimen collection, SP still photography, SS stationary (tether) survey, TC
transect count, TG tagging, TN traditional knowledge through interviews, TS tape and compass survey,
UV underwater visual census, VR video recording, US ultrasound imaging
Table 9.1 (continued)
9 Studying and Monitoring Aggregating Species
9.4 Methods Described
The basic uses and limitations of methods are described below in single paragraphs.
For many topics, more detailed technical information is presented in a subsequent
section and the SCRFA study manual (Colin et al. 2003 , www.SCRFA.org ). For
some additional methods, references are provided.
AF – Artifi cial Fertilization and Gamete Collection
One of the simplest ways to obtain large numbers of fertile eggs from a spawning
aggregation is to collect individuals through diving or fi shing at the time of spawning, hand-strip and mix the gametes. Fish to be speared can sometimes be selected
by sex or size (Colin et al. 1987 ) . Running ripe males can often be obtained some
time ahead, and if maintained alive sperm can be stripped as needed. The sperm of
dead males remain viable in the testes for hours. Testes (either in the fi sh or removed)
can be chilled (but not frozen) for a day or more and the sperm remains viable
(Colin et al. 1996 ) . Eggs must generally be obtained at the time of spawning either
through collection of females ready to spawn or following hormone injections of
fi sh held in aquaria (Watanabe et al. 1995 ) . It is uncertain how long hydrated eggs
can be maintained before fertilization. Standard techniques are used to mix eggs and
sperm for fertilization, followed by fi rst cleavage within an hour or less to confi rm
development.
AM – Acoustic Monitoring
When reef fi shes spawn planktonic eggs, they may produce both hydrodynamic
sounds (noise) and species-specifi c sounds. Potentially these sounds can be monitored by an acoustic receiving system at or near the spawning site and used to
document spawning activity over time (Lobel 1992 ) .
Subject/parameter
F/D or F/I
Method
Location of gametes after release
I
DR, DY, DO
Migration pathways
DI
DO, AT
Key to FD/FI and Methods-FD/FI
D fi shery dependent, I fi shery independent, DI both , AF artifi cial fertilization and gamete collection,
AM acoustic monitoring, AT acoustic tag, BM bathymetric mapping, DO direct observation by
snorkeling or diving, DR drifter release, DY dye release and water tagging, EC egg collection, EM
experimental manipulation, FM fecundity measurements, FS fi shery sampling from fi sher catch,
GC gut contents, GD GPS density survey, GN gonad study, GS genetic sampling, HA hydroacoustic
survey, IS instrument at site, LD longterm database, OT sampling and analysis of otoliths, RV remote
operating vehicle, SC specimen collection, SP still photography, SS stationary (tether) survey, TC
transect count, TG tagging, TN traditional knowledge through interviews, TS tape and compass survey,
UV underwater visual census, VR video recording, US ultrasound imaging
Table 9.1 (continued)