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EcoEarth
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Marine Sanctuaries Work!The contention that Marine Parks and no-take marine sanctuaries have no scientific In 2003, Dr Ben Halpern from University of California Santa Barbara presented an analysis of the results of studies into 89 separate no-take marine reserves around the world. He found that on average, creating a no-take marine sanctuary doubles the density of fish and invertebrates, triples the biomass and increases the mean size of fish by 20-30% relative to fished areas (Halpern, 2003). These results indicate the re-establishment of natural processes after serious disturbance. One clear example of such disturbance is the extensive areas of urchin barrens found on near shore reefs of NSW (Andrew and O'Neil, 2000). Urchin barrens have been linked to the removal of large predators, leaving urchins populations to grow unchecked without adequate predation. Studies of established marine sanctuaries where urchin barrens were present show that affected reef systems have recovered (Parson et al, 2004). While the effects on ecological processes of commercial fishing have been widely acknowledged, recreational fishers have not readily accepted any responsibility for their impacts. As recreational fishers preferentially target large aggressive predatory fish, it is a nonsense to suggest that no impact results. Recent studies have suggested that targeting the largest and most aggressive fish in a population is leading to maladaptive genetic selection for smaller, slower maturing less aggressive fish which has profound implications for productivity and population recovery (Walsh et al, 2006). An example of this process at work can be best seen in the snapper population of NSW. Snapper is recognised as being “growth over-fished” by NSW Fisheries, where the average size of fish landed is declining. Each year NSW anglers catch about 117 tonnes of snapper of an average weight of about 400 grams (the legal weight is about 600 grams). However, in Victoria and Queensland, the average weight of snapper caught by anglers is 1.5 kilograms, and in South Australia the average snapper caught is 3.7 kilograms (BUREAU OF RURAL SCIENCES). Some anglers have suggested that maximum size limits should be introduce as an alternative to marine sanctuaries. Catch-and-release fishing, while commendable, is of limited value. Studies have shown a mortality of over 30% of snapper released after being caught.Long-term mortality (>10 days) of released fish is less well understood, and may be far greater than 30% (DPI Fisheries). As sanctuaries also aid in the recovery of threatened species, such as grey nurse sharks (that recreational anglers also have a significant impact upon) bag limits have far fewer benefits. The spill-over effect of marine sanctuaries warrants attention. Because marine sanctuaries lead to more large fish, the number of eggs produced is much greater. Almost 10 times more eggs can be produced by fish only twice the size of smaller fish. More importantly, the larvae produced by the larger fish have been shown to be more resilient, as they grow three times faster and survive starvation more than twice as long as larvae from smaller fish (Berkely et al, 2004). Further, many studies have shown that predatory fish benefit from sanctuaries to a greater degree than prey species. When predators are removed by fishing, the prey is released from competitive pressure and proliferates. Prey species have been shown to be four times more abundant in fished areas compared to unfished sanctuaries (Graham et al, 2003). You don’t need to be a marine ecologist to understand why predatory fish are more likely to move out of sanctuaries if densities of their prey are more abundant in surrounding fished areas. The Port Stephens – Great Lake and Batemans Marine Park Zoning Plan is a unique opportunity to preserve marine life and allow fished populations to recover. While the benefits will not be immediate, commercial and recreational fishing and coastal communities will benefit from the establishment of no-take marine sanctuaries. The first challenge, however, is to overcome narrow minded self-interest and put marine sanctuaries in place. Click here to see a video of NZ kids finding out for themselves how marine sanctuaries work.
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basis is ignorance, denial, and humbug. 
Spill Over
I am curious to find out how the notion of spill over came about. The assertion appears to be that if we do not take fish from a particular area, the local population will increase beyind the ability of the area to sustain the exploded population and they will spread out into the surrounding area. In the case of marine parks, this must be from the pink (reef) zone to the blue (sandy bottom) area.
If this were true then at the time of the first fleet, "reef fish" would be found on the sand and in the estuaries as there would have been no room for them on the reefs they prefer.
What bunk. The fish will assume a natural balance where the stongest will survive and the weakest will become food.
The notion that has been put forward by proponents of marine parks that fish will live in peace in the marine park is very short sighted and misinformed.
Spill over and big old fat female fish
Firstly, the notion of “spill over” is a bit of a misnomer. The assumption that marine sanctuaries are some kind of enclosed barrel is a misunderstanding of the concept, as much as it is a misinterpretation by opponents and proponents alike. The term spill over effect is, however, still useful to get people to begin understand what is occurring.
In 1990, Dr Jim Bohnsack used stock recruitment curves to argue the position that most fished populations crash once they are depleted below 20% of the unfished biomass. This is now accepted fisheries doctrine, and a useful model for assessing sustainable fisheries. Bohnsack articulated the difficulty in managing mixed marine fisheries, like that of NSW, without removing fishing from geographic areas. He proposed that to remove fishing from 20% of marine areas would provide an adequate buffer to stock collapse, as it would likely provide an unfished biomass of 20% of the stock regardless of the management or mismanagement of the fishery. The natural progression from this position is the removal of fishing from a representative set of marine habitats, ie near shore, mid depth and deep reefs, muddy and sandy substrates, seagrass etc, to assure a buffer for a corresponding suite of fished species.However, sanctuaries are rather useless if they only focus on commercial fishing, particularly as the depletion of fish stocks has been so severe. Failing to include recreational fishing denies its very real impacts (reading the article as well as the papers attached will explain these impacts in more detail), as well as the perilous situation many fished populations are in.Secondly, due to fishers targeting carnivores, herbivores are not benefited by marine sanctuaries – ie their numbers are not increased by removing fishing from the area they inhabit, as herbivore fish are not generally targeted by recreational fishers. Indeed they are impacted by sanctuaries in that sanctuaries lead to greater densities of carnivores, and therefore a reduction in herbivore density compared to fished areas. When the “balance” is reinstated within sanctuaries, the fished areas or the “unbalanced” areas contain higher densities of herbivores. Spill over works precisely because there has been a reduction in the population due to fishing. A spill over would not operate in a "natural balance". But that is not what we have, is it? Fishing, and in many cases severe over-fishing has caused an unnatural imbalance in ecological processes and population dynamics.
Thirdly, the assertion that the strongest fish will survive and weakest fish become food is overly simplistic. Recreational fishing in particular target the largest and most aggressive fish in a population: Therefore those fish that risk taking bait. This is leading to unnatural genetic selection for smaller, slower growing, less aggressive fish.
Big, old fat female fish are the basis for a healthy fish population because they produce so many more eggs. The larvae from these eggs grow faster and survive longer than those from smaller, younger fish. Vigorously growing young fish do not have the available nutrients for egg production as do fish that have reached maturity. Far from being short sighted and misinformed, making sure that an adequate proportion of big old fat female fish survive is a sensible precautionary approach to fisheries management.
The first step to understanding is to put asside our prejudices and self interest.