Postlarval Fish Capture and Culture for Restoring Fisheries | 21

ABSTRACT

The management and use of marine fisheries, regardless of the scale at which they occur, involves removing a part of the stocks, which are often limited and finite� This presents a real problem because for certain species, these stocks are increasingly depleted and sometimes even exhausted� Such overexploitation of resources is evident not only for food species, but also for reef species that are popular for the aquarium fish market�

In general, most fishing techniques take adults, often breeders, thereby diminishing not only current stocks but also future stocks� Open-ocean fishing techniques, whose destructiveness varies depending on the technique used, such as gillnets, and the amount of fish caught, do, however, spare habitat� This is not the case for coral-reef fishery techniques, which, depending on the method employed, can directly affect habitat conditions, such as using cyanide and explosives� Russ and

CONTENTS

Introduction �� 179 Overview of the Life Cycle and Nonimpact of Postlarvae Collection �� 180 Postlarvae Fishing Techniques: The Four Main Methodologies �� 181

Crest Nets Set Up on Barrier Reefs �� 181 Hoa Nets Set Up between Small Islands on Reef Ridges �� 181 Light Trap �� 182 Collect by Artificial Reef Eco-Friendly �� 182 Postlarval Capture and Culture �� 183 Market Opportunities �� 183 Alternative Aquarium Fish Farming �� 183 Supplementary Aquaculture �� 184 Restocking �� 184 Restocking as Mitigation for Maritime Impact �� 185

Postlarval Capture and Culture as a Provider of New Eco-Jobs �� 186 Conclusions �� 186 Perspectives �� 187 References �� 187

Alcala (2004) found that 75% of the coral reefs in the Philippines have been damaged from such practices� In other words, not only is there overfishing, but also fish habitats have been destroyed, leaving nature with no way to recover from such disturbances�

Eggs, larvae, and postlarvae of marine fish and crustaceans are usually considered to be a nonexploitable marine resource, as opposed to juveniles and/or adults, which are actively harvested� Recent books shed light on the rarely described stages of those postlarvae (Juncker 2007; Lecaillon et al� 2012; Maamaatuaiahutapu et al� 2006)�

The approach of postlarval capture and culture (PCC), however, develops these previously overlooked resources through the capture and rearing of presettlement postlarvae� Adults reared from postlarvae can then be a genuinely sustainable alternative to the capture of wild adult marine animals for a variety of species, including both high-quality food fish and valuable ornamentals� This is not as far-fetched as it sounds, because the postlarvae stage is the final stage of the pelagic larval phase of coastal marine animals, which ends with the colonization and settlement of the postlarvae into their habitat, usually a coastal environment such as coral reef or rocky or sandy shores� Most demersal (bottom-dwelling) reef fish species have pelagic (open-ocean) larvae� However, after metamorphosis to juveniles, these postlarvae suffer catastrophic mortality rates during the settlement process, with more than 95% dying within the first week of their return, mainly due to predation (Doherty et al� 2004; Planes and Lecaillon 2001)� By capturing an insignificant proportion of these postlarvae before the mortality phase, we effectively exploit a resource that would otherwise be largely, and naturally, wiped out (Bell et al� 2009; Lecaillon and Lourié 2007)�

Collection of postlarvae is certainly not the only solution to the overexploitation of demersal species, but it is nevertheless a path worth exploring, not only for developing an innovative and sustainable type of aquaculture, but also for repopulation efforts, which are just beginning (Delbeek 2006)�

OVERVIEW OF THE LIFE CYCLE AND NONIMPACT OF POSTLARVAE COLLECTION

Most coastal fish (not only coral-reef fish, but also demersal fish in temperate zones) have oceanic larval phases at the beginning of their life cycles (Leis 1991; Leis and Carson-Ewart 2000; Sale 1980)�

This phase allows them to colonize new habitats, thereby facilitating the species’ broad distribution and, consequently, their persistence (Choat and Robertson 1975; Lobel 1978; Victor 1986)� Depending on the species, larvae spend from 20 days (Pomacentridae) to more than 100 days (Aulostomidae) in the open ocean (Brothers et al� 1983; Victor 1986; Victor and Wellington 2000; Wellington and Victor 1989)� Size of postlarvae range from 6 mm to 80 mm for a large majority of fishes (see Figure 16�1)� Fairly passive during most of this phase, they finally become active-they enter their competence phase (Cowen et al� 2000; Doherty and Williams 1988; Fauvelot et al� 2003)—to look for their new habitat� This settlement phase takes place at night, if possible, when there is no moonlight� Still, most of those postlarvae (more than 95%) disappear during the week that follows settlement, mainly due to predation (Doherty et al� 2004; Planes and Lecaillon 2001; Planes et al� 2002)�

Postlarvae collection techniques make it possible to recover these animals before this phase of high natural mortality� Given the very large number of postlarvae arriving from the ocean, collecting a small percentage of them has almost no impact (Bell et al� 1999, 2009)� These techniques provide access to a previously unexploited marine resource, without impacting stocks or damaging the environment (Lecaillon 2004; Lecaillon and Lourié 2007)�

Today, thanks to a range of existing collection tools and the know-how developed by certain private and public agencies, these postlarval fish can be kept alive, weaned, and grown out to become a new marine resource, while respecting the spirit of sustainable development and biodiversity conservation�

POSTLARVAE FISHING TECHNIQUES: THE FOUR MAIN METHODOLOGIES

The following techniques are described in the Moana Initiative (2007) booklet�

Crest Nets Set Up on Barrier Reefs

This technique consists of setting up a net on the barrier reef that encircles the lagoon, with the open end toward the ocean, to catch the postlarvae surfing over the crest to get into the lagoon� This technique was developed by French and Australian laboratories (Ecole Pratique des Hautes Etudes [EPHE] of Perpignan) (Dufour 1991) (Australian Institute of Marine Science) in collaboration with the WorldFish Center (Hair and Doherty 2003)� A private firm based in Moorea, French Polynesia, which is no longer in business, used it�

Setting up the nets requires a significant number of staff to put up, on the reef crest, the poles needed to prop up the net� The equipment wears out quickly, because it is constantly hit by waves� These nets can be used only near amphidromic points (where tidal ranges are very small) and, by definition, in those areas where there are crests/ridges, which considerably reduce the number of countries where the technique can be used� For instance, these nets cannot be used in temperate settings� Finally, the crests sometimes have a lot of Sargassum-and Turbinaria-type seaweeds that get caught in the collector that can abrade the postlarvae and damage them�

Hoa Nets Set Up between Small Islands on Reef Ridges

Certain islands, particularly coral atolls, have very shallow (2 m) channels on their reef ridges, surrounded by dry land (called motu in Polynesian)� The channels, called hoa in Polynesian, meaning “marine rivers,” allow the ocean to fill the lagoon� This technique consists of setting a net across these hoa to catch the postlarvae concentrated in the water masses passing between the motu and entering the lagoon�

When a site has a hoa, setting up the net is simpler than for crest nets� The force of the waves on the gear is smaller, so it is easier to set the net up and take it down� This device traps everything going through the hoa and so is very effective� It is sometimes the victim of its high level of effectiveness, because when the postlarvae of a given species are particularly abundant, millions of postlarvae can be caught� But because there are too many of them in the collector, most die from a lack of oxygen� This is not profitable for either the fisher or the environment�

This technique arose from the efforts to optimize the use of crest nets and so has appeared more recently� Of course, one must have a hoa to use the method� Unfortunately, these geomorphologic

structures are even rarer than reef ridges, so use of this technique is, once again, geographically limited� A private firm based in Bora Bora, French Polynesia, used it mainly for ecotourism restocking�

Light Trap

Many different models of light traps exist, because scientists have used this method for many years� First developed by the Australians (Doherty 1987), then optimized by the French, it consists of a casing surrounding an autonomous underwater lamp� Postlarval fish, attracted by the light, are trapped when they go through the slots into the trap�

This technique is widely used for scientific missions, because it can be set up rapidly (Watson et al� 2002)� All one has to do is deploy it; no reef ridges or hoa are needed, so it can be used anywhere� Light traps have their limits, however, because the postlarvae have to find the slots (vertical in the French model and horizontal in the Australian model) to be trapped, and this reduces their effectiveness� In addition, certain small pelagic fish (e�g�, sardines) are also attracted to the light, and, because of their horizontal swimming style, get trapped, panic, and then die�

Collect by Artificial Reef Eco-Friendly

Collect by Artificial Reef Eco-Friendly (CARE) is a new technique that was recently developed by a French company (patented by Ecocean in 2002; www�ecocean�fr)� It uses a lighted artificial reef that takes advantage of the behavior of new recruits to trap them; that is, their attraction to light (phototropism), desire to come in contact with a solid object (thigmotropism), and desire to find shelter from predators� These sensory elements are important for postlarval fish, which have very acute senses during recruitment (Lecchini 2003; Sweatman 1988)�

This technique has the advantages of light-trap fishing, while being more efficient and free of the problem of attracting pelagic species� It attracts the postlarvae of reef or demersal species that are in the settlement phase� The postlarvae choose to take shelter in the artificial reef, while unwanted small pelagic fish just swim over the reef�

A new smaller and cheaper recent version (2012) of the CARE trap has been specially designed for ease of use in developing countries and other locations where specialist technical support may not be available:

Postlarval Capture and Culture

A new technique used to collect and rear the marine resource is called PCC� Breeding marine fish is highly expensive, labor-intensive, and technically difficult� However, PCC offers a solution whereby Mother Nature does all the hard work, and where the abundant hatcheries of the sea can provide large quantities of postlarval fish with relative ease�

The PCC technology involves the following steps:

Market Opportunities

Depending on the year and site, part of some postlarval fish and shrimps collected (average of 30%) can go to the ornamental market (e�g�, butterfly fish and damselfish), especially because marine aquarium fish fetch a high unit price when there is a market for them� Some (average of 40%) can be used for aquaculture (e�g�, rabbit fish, groupers, and snapper), but all can provide income for local fishers, with the added benefit that postlarval collecting and rearing reduces fishing pressure on the already stressed fish stocks in the area�

Alternative Aquarium Fish Farming

Here, opportunities exist mainly in developing countries like the Philippines and Indonesia, whose current levels of exported aquarium fish account for 80% of the world market� The steps for postlarvae collection, grow-out, and shipping are very well known, and several trials have

been successfully carried out in the Reunion Island, Comoros, Hawaii, French Polynesia, and the Philippines� Actually, in the Indian Ocean, two entities-MadaFia (Madagascar island) and EcoFish Mauritius (Mauritius island)—are running a business for marine aquarium trade� On an average, about three months of grow-out are needed to get fish of a “small” marketable size (less than one month for Pomacentridae but more than four months for Labridae and Chaetodontidae)� Reared juveniles caught as postlarvae stage also become accustomed to human handling and to elevated levels of fish by-products in their tanks� In this way, they become adjusted to the tank environment, and as they acclimatize, they become much less prone to stress� Therefore, they are much easier to transport and to keep in captivity if sold into the ornamental trade�

This new procedure makes it possible to produce immunized and disease-resistant specimens, thereby bringing a certain level of quality to a declining market for a wild product, which has mortality rates of up to 90% between the points of collection and final purchase by aquarium-fish lovers (Schmidt and Kunzmann 2005)�

In summary, tank-raised fish from postlarval collection offer many benefits both for conservation and for the marine aquarium trade� They reduce the number of wild-caught fish, which in turn decreases the pressure from marine ornamental collectors on coral-reef habitats� In addition, their acclimatization, freedom from disease, and general hardiness improves life span in marine aquaria and enhances demand for such eco-friendly fish while reducing pressure to restock aquaria due to fish mortality�

Supplementary Aquaculture

Here again, opportunities exist mainly in developing countries� This activity can provide ciguatera-free protein for local consumers as well as a product that could be destined for the Asian live fish market�

It should be noted that most food-fish families have “large” (> 2 cm) postlarvae, which makes it possible to produce meal-portion-sized specimens after about six to eight months of in-cage growout� Currently, trials are under way in Madagascar, in collaboration with Institut Halieutique Service Maritime (Tuléar)� Initial results for the in-cage grow-out of species of Siganidae and Lethrinidae indicate growth coefficients that were 1�8 times greater than those in land-based tanks�

Another project underway (September 2006-September 2007) in the Philippines, with funding from the US-based National Fish and Wildlife Foundation, is attempting to transfer knowledge about larvae harvest techniques to local communities� This project has the unanimous support of the various fisher, farmer, and decision-maker circles� The farm belongs to a local nongovernmental organization (NGO) Feed the Children, and the operational project is part of a Coastal Resource Management Plan set up by the Municipality of Tubigon� This project also has the goal of repopulating a local marine reserve with some 10,000 juvenile fish�

Some developed countries may also be interested in collecting postlarvae, particularly to study the growth rates of certain target species before attempting to improve particular reproduction phases (e�g�, increasing gamete production rates, limiting stress, etc�) Finally, biotechnical companies could be interested in the biomolecules contained in oceanic postlarvae, which have low parasite levels�

Restocking

Although new jobs can be created through aquaculture production for ornamental markets or for consumption, a percentage of the stocks collected should always be returned in the form of restocking in Marine Protected Areas (MPAs) (Lecaillon and Lourié 2007)�

Restocking of different coral-reef fish species from postlarval collection is an entirely new concept� Once grown and prepared, juveniles are brought to the restocking location� Once divers have released the fish, marine scientists from local NGOs or academic institutions who also study their behavior

monitor and count survival rates� Experiments have shown good results, where released fish were still near restocked habitat after two weeks� Juveniles have wild behavior a few hours after the release�

The impact of restocking can be measured against the baseline data already collected prior to restocking� These data include habitat as well as the condition and abundance of fish and invertebrates� Tagging has been tested, but suffers from several disadvantages (cost, time, stress to fishes during the tagging procedure, etc�)� Results are determined through a long-term process of counting fish population before restocking and at regular intervals after restocking of the site, and comparing the results with a local control area with similar habitat and fishery characteristics (to ensure like-to-like comparison)�

The successful restocking of juveniles may also lead to synergistic effects on the recruitment of other larval fishes from outside the MPA (due to noise and pheromone attraction)� Genetic diversity is often lower in disturbed and degraded areas, with a possible risk of extinction� Postlarvae collected by the CARE trap have higher genetic diversity than the resident adult fish population, as they have not yet undergone major mortality events� Therefore, restocking with the resulting juveniles will increase genetic diversity and ensure population continuity (Frankham et al� 2002)�

Ideally, restocking should focus on species that are either lacking within the restocking area or whose characteristics fit the needs of the MPA� For example, if coral-reef cover is low and algae are abundant, algal grazers can be introduced to clear the algae, which in turn should enhance new coral recruitment within the MPA�

The restocking activities can also help promote the local MPAs and open up the area to improve tourism� Restocking (or monitoring) is well suited to this kind of destination� Fisher families may earn additional income by providing transport, accommodation, and food, and guiding visitors through the MPA and the restocking facility� The potential for such activities has yet to be fully explored�

In any restocking case, juvenile release must be done according to microhabitat� The best results are found where habitat structures of suitable size and shape provide shelter for juveniles against predation, such as natural or artificial mangrove roots (Cocheret de la Moriniere et al� 2004; Nagelkerken and Faunce 2007, 2008; Nagelkerken et al� 2010; Verweij et al� 2006) or Biorock structures (Goreau 2010)� These microhabitats can be diverse, and Biorock will work perfectly for juvenile restocking from postlarval collection�

Restocking as Mitigation for Maritime Impact

Finally, a process named BioRestore© has just being validated in 2011 as a mitigation measure for coastal projects (https://www�ecocean�fr/en/ecological-restoration-applications�asp)� This process will include a postlarval capture step, a specific culture onto small juveniles step, and a restocking step associated with microhabitats (see Figure 16�3)� BioRestore® is custom-made for companies,

NGOs, cooperatives, municipalities engaged in sustainable coastal development, ecological restoration, mitigation for unavoidable impacts, and coastal infrasctructure projects such as ports, marinas, off-shore energy, seafloor mining and underwater pipelines�

As at totally sustainable process involving local stakeholders, BioRestore® can facilitate community and government acceptance of the project, while at the same time enhancing the knowledge of local marine biodiversity� BioRestore® helps to restore impaired marine ecosystems and boost ecological resilience towards self-sustainability�

POSTLARVAL CAPTURE AND CULTURE AS A PROVIDER OF NEW ECO-JOBS

The United Nations Education, Scientific and Cultural Organization (UNESCO) through its Man and Biosphere program (MAB), has funded a booklet about the eco-jobs that are economic opportunities generated through environmentally oriented capacity-building� The following jobs are among those that can be created through a postlarval collection and rearing project, implemented with and for local people, through the conservation and sustainable use of coastal and marine biodiversity (Moana Initiative 2005):

CONCLUSIONS

PCC has a double positive impact: 1-Collection from within a huge nonexploited natural stock enables a reduction of fishing effort on the normally exploited stock� 2-This will save future genitors, allowing production of an increasing number of saleable products from abundant postlarval stock� The high-quality fish resulting from the eco-friendly collection of postlarvae are extremely robust, exhibiting a high rate of survival, because tank-raised fish are better suited to life in fish farms, sea cages, or aquaria� They are accustomed to human handling, acclimatized to wastewater in their tanks, and are weaned on pellets�

… and no known negative impacts� The nonimpact of PCC technology on the marine environment is widely validated by the

scientific community� PCC has been already tested in several countries and regions, such as the Philippines, French Polynesia, Madagascar, Fiji, Comoros, Hawaii, Florida, and the Mediterranean Sea� There is ample proof of concept�

As a consequence, PCC technology has already been labeled “good practice” by the International Coral Reef Initiative (www�icriforum�org)� Organizations such as the UNESCO, through its MAB program, have found PCC suitable for building quality economies through the conservation and sustainable use of coastal and marine biodiversity� A recommendation from the Ministry of Environment in France concerning the use of PCC has just been included in the “Grenelle de la mer” last June 2009 (https://www�legrenelle-mer�gouv�fr/IMG/pdf/LIVRE_BLEU_Grenelle_Mer �pdf)� PCC is a completely new and fully sustainable technology, because it effectively creates “something from nothing” by exploiting a resource that would otherwise simply be overlooked�

PERSPECTIVES

A PCC-based aquaculture project uses an eco-friendly technology, which is quite simple to set up, and can generate employment and new income for local communities in developing countries� The use of PCC also serves to reduce the pressure exerted on adult reef fish by offering access to a new and un-or underexploited marine resource�

However, PCC’s application is not limited to tropical seas and developing countries� It is also suitable for use by advanced nations in temperate seas as an additional economic, conservation, and restocking resource (mitigation banking), especially where conventional conservation strategies have already failed� The heavily overfished Mediterranean and North Sea fisheries are good examples of areas that could benefit from such an approach� A new project called GIREL has just started to mitigate Marseille Harbor impact�

Finally, PCC is an excellent tool to study and understand this little-known part of the life cycle of coastal marine species� Thanks to Ecocean’s automation of the postlarvae capture processes, complete with timing devices if needed, PCC can be used in any marine environment for research and monitoring of planktonic biodiversity� A LIFE and EU funded project has just been funded about larval fish biodiversity using CARE devices and PCC technology (Life10/NAT/FR/00200)� LIFE is the EU’s financial instrument supporting environmental and nature conservation projects throughout the EU� This project named SUBLIMO, is hosted by the University of Perpignan in South of France�

REFERENCES