The nature of many spawning aggregations makes the fish populations that form them extremely vulnerable to over-fishing when fish are migrating to, and while at the aggregation site. For this reason the aggregation period and site usually require specific management measures to ensure the survival of spawning aggregations and, therefore of fish populations.
There are a number of different options available for managing and conserving spawning aggregations. The following summary and overview are taken from a Working Group report on spawning aggregations conducted in 2002. The summary addresses the advantages and disadvantages of a range of management options. The most suitable management for a particular location inevitably depends on a range of social and economic contexts, and is best made on a case by case basis.
Of all the spawning aggregations for which we have information in the SCRFA database, most are not yet managed. Of those that are managed, marine protected areas, time and area closures and sales bans are the most common approaches, often in some combination. For example, a temporary spawning site closure if often accompanied by a sales ban to assist enforcement.
There are a number of management options specialized for fishes that form spawning aggregations, including Seasonal closures-no area closure , Short-term area closure, Short-term time and area closures, and Fully-protected areas. Click on the name of the management options to know more about each of them.
Seasonal closures-no area closure (the fishery for the managed species is completelyclosed for the spawning season with no catch or sales of the species permitted; there isno attempt to protect the actual spawning area)
- Pros: relatively easy for enforcement since fish should not be for sale in markets or in possession; site-specific information not needed since seasonal closure will protect species; effective if significant catch occurs outside the spawning aggregation during the reproductive season; protects spawning aggregation male/female social structure; intuitive so relatively easy to accept; protects fish that are aggregating in deep waters (and which would be used for live reef fish trade) from high levels of wasteful mortality; protects other species that aggregate at the same time, but little is known about these species spawning behaviour.
- Cons: which species should be protected (i.e. which season[s] or species must be selected for seasonal closures); could be circumvented by having fish held alive until season is over; spawning aggregation site could be damaged by other activities.
- Information needs: timing variability of reproductive season that could vary even within a relatively small area for a single species
Short-term area closure-no seasonal closure (the aggregation site is closed for the duration of the spawning season of the managed species but fishing for this species can continue outside the spawning aggregation area)
- Pros: protect spawning habitat in the short-term (since focus in area may only be during spawning aggregations) and the fish that spawn there; protects spawning aggregations male/female social structure; protects multi-species; protects fish that are aggregating in deep waters (and which would be used for live reef fish trade) from high levels of wasteful mortality; intuitive so relatively easy to accept.
- Cons: this option has high compliance costs if spawning sites are remote and widely spaced; decision must be made over which areas to close and vessel monitoring systems (VMS) may be needed to ensure compliance and these can be expensive; not useful if most of the catch is taken outside of the spawning aggregation. Provides only short-term protection of the spawning aggregation site from physical damage. When an area is reopened to fishing, fish stocks that might have been replenished will be depleted quickly unless strict management controls are implemented.
- Information needs: connectivity of sites and the areas which the adults use within the spawning season will determine the most relevant sites and their sizes for protection if all spawning aggregations cannot be protected – this means that year to year variability in use of specific spawning aggregation areas must be determined; area to be protected might have to incorporate migration routes of adults into the spawning aggregation.
- See the two measures given above; solves the problem of having to decide specifically closure times and areas; probably easier to enforce overall. Involves a seasonal sales ban that would be most effectively implemented as there were only a few major markets.
- Pros: protects habitat permanently; global support for fully protected areas is growing and such protection is intuitive in some communities; very probably a higher overall fishery advantage than short-term closures because the protected area could act as a source of young for a wide range of species not otherwise protected by seasonal or short term area measures; ensures complete protection of aggregations considering the uncertainty of spawning seasons and locations; ensures protection of spawning site habitat; needs research to identify appropriate areas for protection.
- Cons: harder to justify than a short term area measure because the impact on nearby fishing communities is likely to be greater; if area is not properly placed or large enough, the benefit may not be apparent or sufficient and the approach difficult to support in the long term; enforcement more onerous than short-term protection.
- Information needs: connectivity with other areas or biological importance of protected area; are key habitats being included? How big should the area be? If there are many FSAS in an area, maybe the whole area needs to be included in a closure rather than many small closed areas that are very hard to enforce.