Reviews in Fish Biology and Fisheries 13: 141–149, 2003.
© 2004 Kluwer Academic Publishers. Printed in the Netherlands.
Stock enhancement and sea ranching: objectives and potential
Borneo Marine Research Institute, Universiti Malaysia Sabah, 88999 Kota Kinabalu, Sabah, Malaysia
Introduction page 141
Stocking objectives 143
Types of sea ranching 143
Necessary basic scientiﬁc information 143
Concerns and scientiﬁc answers 145
An increasing seafood demand together with the
decline or stabilization of most of the global
marine ﬁshery resources and increasing proﬁciency
in aquaculture are essentially responsible for the
enhanced interest in sea ranching. The world produc-
tion from capture ﬁsheries has leveled off or declined,
after reaching a peak of 88.67 million tons in 1989.
Reckless exploitation of marine living resources,
disruption of ecological links and damage to critical
habitats have created a situation whereby many wild
stocks that had traditionally supported commercial
ﬁsheries are no longer able to replenish abund-
ance through reproductive recruitment and are unable
to regain their adaptation and genetic variability.
Although the ocean resources are resilient, they are
not inexhaustible. Overﬁshing and habitat destruction
have reduced the catch of many species and despite
reorientation of management approaches their popula-
tions have not responded. What other evidence do
we need to prove exhaustibility of ocean resources?
Since the sea is the last frontier for exploitation on this
planet, we must seriously ponder over consequences
of reckless exploitation of its living resources for our
life-support systems. Human population has exceeded
6 billion and continues to grow. We will be increas-
ingly dependent on sea resources. Without taking care
of these resources and applying new management
tools sustained supplies from the sea are unlikely.
The contribution of aquaculture to seafood produc-
tion cannot be overemphasized. It increased the global
ﬁsheries production to over 140 million tons in 2000
(FAO Fishery Statistics). However, a number of inputs
required in aquaculture operations increase the cost of
the product, often substantially. Also, there are several
aquaculture practices that fail to sustain production on
a long-term basis for a variety of reasons. An opinion
is gaining ground that we must provide something to
the sea to be able to obtain returns of high quality
food for our population. Providing resources to the sea
actually refers to releasing juveniles of animals that
have been caught from the sea and induced to breed
in hatcheries. Reseeding these stocks appears to hold
good prospects of increasing production.
Environmental and biological effects of sea
ranching are still being determined for most species
but there are compelling reasons to believe that if
carried out scientiﬁcally, it will offer an economi-
cally viable means of restoring depleted stocks and
increasing production from coastal and marine ﬁsh-
eries on a sustainable basis.
Twenty-seven countries are currently involved with
ranching of more than 65 marine or brackish water
species in addition to over 60 more species that are
being researched for stocking by Japan (Bartley, 1995,