7 Genomic Approaches in Aquaculture and Fisheries
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4. Eggs are produced in large numbers and fertilised externally. The older
(and larger) the fish, the more eggs (often of a better quality) are produced
(Marteinsdottir and Begg 2002). The most common breeding strategy is mass
spawning: some species brood their eggs, such as nest guarding gobies, pouch
brooding (e.g. pipefishes) and live-bearers (e.g. Sebastes spp.). Despite the huge
numbers of progeny and the huge potential for population growth, adult population sizes remain relatively constant. This is largely due to the high selection
pressure at the early life stages. Eggs, larvae and young post-larvae are massively
preyed upon and even cannibalised. But infections, failed fertilisation, oceanic
drift to suboptimal “sink” habitats, maternal effects and genomic incompatibilities also cause extensive mortalities (King 1995). Typically, the contribution of
spawners to the next generation is not equally distributed between individuals
and genders. Only a few parents contribute significantly to the progeny, while
most do not contribute at all.
5. The last point to mention is that given the high level of connectivity, genetic
population structure might be real but is also weak, usually an order of magnitude smaller than in continental systems (Ward et al. 1994, Cowen et al. 2006).
“Metapopulations” conceptualise the patterns and dynamics of fish communities
(Hanski and Gaggiotti 2004). Patterns and dynamics are strongly determined by
the landscape in which they spend their early life-history, feed as (sub)adults and
mate (Jørgensen et al. 2005). An alternative perspective is the “member-vagrant”
concept (Sinclair 1988), where propagules may or may not successfully colonise
new habitats.
From the above-mentioned characteristics of marine fish and their habitat the key
questions from a genetic perspective can be reformulated as:
• What is the historical and contemporary genetic diversity, its causes and dynamics?
• What are the historical and contemporaneous genetic patterns (neutral evolution),
their causes and dynamics?
• What are the historical and contemporary patterns of adaptive evolution, be it
either natural or anthropogenic in origin? What are their causes and dynamics?
Some aspects of population genomics have great relevance for the goods and
services they deliver to society.
• The tracing of populations is a cornerstone for ecosystem-based fisheries and
conservation management.
• The tracing of food stuffs is a commonly applied tool for law enforcement and
quality assurance
• The tracing of populations and individuals is of fundamental importance to allied
research disciplines (ecology, physiology and behaviour).
• Diversity at the population level has helped to discover and understand novel
substances for biotechnological applications.
251
4. Eggs are produced in large numbers and fertilised externally. The older
(and larger) the fish, the more eggs (often of a better quality) are produced
(Marteinsdottir and Begg 2002). The most common breeding strategy is mass
spawning: some species brood their eggs, such as nest guarding gobies, pouch
brooding (e.g. pipefishes) and live-bearers (e.g. Sebastes spp.). Despite the huge
numbers of progeny and the huge potential for population growth, adult population sizes remain relatively constant. This is largely due to the high selection
pressure at the early life stages. Eggs, larvae and young post-larvae are massively
preyed upon and even cannibalised. But infections, failed fertilisation, oceanic
drift to suboptimal “sink” habitats, maternal effects and genomic incompatibilities also cause extensive mortalities (King 1995). Typically, the contribution of
spawners to the next generation is not equally distributed between individuals
and genders. Only a few parents contribute significantly to the progeny, while
most do not contribute at all.
5. The last point to mention is that given the high level of connectivity, genetic
population structure might be real but is also weak, usually an order of magnitude smaller than in continental systems (Ward et al. 1994, Cowen et al. 2006).
“Metapopulations” conceptualise the patterns and dynamics of fish communities
(Hanski and Gaggiotti 2004). Patterns and dynamics are strongly determined by
the landscape in which they spend their early life-history, feed as (sub)adults and
mate (Jørgensen et al. 2005). An alternative perspective is the “member-vagrant”
concept (Sinclair 1988), where propagules may or may not successfully colonise
new habitats.
From the above-mentioned characteristics of marine fish and their habitat the key
questions from a genetic perspective can be reformulated as:
• What is the historical and contemporary genetic diversity, its causes and dynamics?
• What are the historical and contemporaneous genetic patterns (neutral evolution),
their causes and dynamics?
• What are the historical and contemporary patterns of adaptive evolution, be it
either natural or anthropogenic in origin? What are their causes and dynamics?
Some aspects of population genomics have great relevance for the goods and
services they deliver to society.
• The tracing of populations is a cornerstone for ecosystem-based fisheries and
conservation management.
• The tracing of food stuffs is a commonly applied tool for law enforcement and
quality assurance
• The tracing of populations and individuals is of fundamental importance to allied
research disciplines (ecology, physiology and behaviour).
• Diversity at the population level has helped to discover and understand novel
substances for biotechnological applications.