Tuesday, January 17, 2012

Where is the science


Alfredo
Attached is my letter to the BFAR Director which critiques the multimillion peso Mangrove Project featured in 2 recent articles in the MAP Newsletter.
Jurgenne

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15 January 2012

Atty. Asis Perez
Director, Bureau of Fisheries and Aquatic Resources
Quezon City
Fax 02-929-8074
Dear Director Perez

The Department of Agriculture and the Bureau of Fisheries and Aquatic Resources (BFAR) are to be commended for your pro-environment and pro-poor Mangrove Project with funding of ~PhP280 million (Philippine Daily Inquirer, 31 Oct. 2011 and 30 Dec. 2011). Given the substantial amount of public funds, may I share the following observations and concerns pertaining to the three project components.

A. Mangrove Planting – This targets 11 million propagules covering 3,667 hectares for 2012 (of a total 100 million propagules over the next 3 years), and rightfully gives priority to abandoned government-leased (or FLA) fishponds. Though sociopolitically problematic, these ponds are the ecologically correct sites for rehabilitation as they were former mangrove forests. In contrast, past mangrove rehabilitation programs focused on noncontroversial, open access seafront sites – planting by convenience, not by ecology. These less than favorable sites yield low survival, and mangroves will suffer even more if planted where coastlines are vulnerable to sea level rise due to Climate Change.

Hence, it would be prudent to reserve most of the budget allocated for mangrove rehabilitation to reversion of abandoned ponds, and use only a small fraction for seafront planting, unlike past programs. The BFAR project should support moves to streamline the cancellation process for abandoned, unutilized and underdeveloped FLA ponds and their reversion to DENR. To date, very few AUU government ponds have been cancelled, and these few ponds are declared open and available to new applicants, instead of reverting to mangroves as mandated by law.
   
Moreover, sustainable aquaculture requires 4 hectares of mangroves for every hectare of pond (Saenger et al, 1983). Only 248,000 ha of Philippine mangroves remain while culture ponds have increased to 230,000 ha, giving a ~1: 1 mangrove-pond ratio, which means we have a long way to go to restore the required 4:1 ratio. Our best bet in increasing mangrove hectarage is by reverting tens of thousands of hectares of abandoned ponds, and not the ecologically difficult rehabilitation of seafronts.

B. Aquasilviculture – Described as mangrove farming, the reported objective of this component is to grow fish, shrimp and other aquatic crops in the newly planted mangrove areas. Following are some relevant considerations, based on research at the SEAFDEC Aquaculture Department.

Aquasilviculture combines cultured crops with mangrove trees either in the same stand, or in separate ponds.  Whereas mangroves need the regular ebb and flooding of sea water, aquatic species like shrimp and fish require a permanent water column, therefore the trees and animals are incompatible. Following the first model, only mud crabs which can withstand exposure during low tide can be farmed inside mangrove netpens – provided the trees are fully grown and not the newly planted seedlings envisioned in the BFAR proposal, as crabs will consume the tender leaves of the latter (Primavera et al, 2009). Moreover, canals that provide shelter in the low tide should be dug in the center of the pen away from the net enclosures because the crabs can burrow deep in the mud and escape to the outside.

The 2nd Aquasilviculture model features mangroves as biofilters for separate intensive shrimp/fish ponds, requiring 2-8 hectares and up to 20 hectares, respectively, of mangroves to process the nitrogen and phosphorus effluents produced by one hectare of adjacent pond (Primavera et al, 2007). These ratios may even be higher than the 4:1 required for aquaculture sustainability and environmental health.

C. Multispecies Hatcheries – These simple, community-based facilities are to serve as “lying-in centers” where gravid females of crabs and other high-value species will be allowed to spawn and/or hatch their eggs, and young larvae released in adjacent mangroves.

However, newly-hatched larvae of marine crabs, shrimps and fish need the full salinity (30-35 parts per thousand or ppt) of near/offshore waters to complete their larval stages. Therefore they cannot be released in intertidal mangrove waterways which often have fluctuating salinity levels that go down to 5-10 ppt. Even if salinity remains high enough for survival, the vulnerable larvae will still need to fend off predators and learn how to forage, hence their mortality rates are expected to be high. For such planned releases to contribute significantly to wild fish and shellfish populations, the scientific guidelines of Stock Enhancement – an established discipline of fisheries – will need to be applied.

Protocols not only for Stock Enhancement, but also for the other BFAR Project components (which have yet to be spelled out), must be science-based to improve the chances for success of this multimillion peso project. As far as I know, the BFAR has yet to officially consult the aquaculture and mangrove scientists of the country.

J.H. Primavera, Ph.D.
Pew Fellow in Marine Conservation
Scientist Emerita
      SEAFDEC Aquaculture Department
     Tigbauan, Iloilo
Project Manager, ZSL Community-Based Mangrove
      Rehabilitation Project in the Philippines
      132 Quezon St., Iloilo City 5000

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