Long-term action is needed to protect pipi populations
EcoNetwork-Port Stephens has called on the New South Wales Government to adopt more rigorous policies to protect pipi populations, which are in serious decline on the Australian east coast.
President Dr Bruce Pease sent the following letter on 5 March 2012 to the Hon. Katrina Hodgkinson MP, Minister for Primary Industry:
As you have stated publicly, the pipi population is in decline on the whole east coast of Australia, some say to an alarming degree, indicating significant recruitment failure. This being the case, it is imperative that spawning stock be protected from all harvesting activities. Closure to commercial harvesting for six months, while a positive move, will not provide the required protection, nor allow time for effective scientific monitoring to determine causes of decline and assess recovery of the population. Accordingly, we call on the NSW Government to extend the 6-month closure of the commercial fishery to a minimum of two years, with an accompanying scientific monitoring program followed by a review of pipi stocks prior to re-opening the commercial fishery.
We further recommend that regardless of whether pipi stocks reach a ‘sustainable, viable and healthy level’ as you have stipulated, all ocean beaches in all NSW marine parks be closed to hand gathering by both commercial and recreational fishers indefinitely to provide long term conservation of pipi spawning stocks in NSW. Closures should be reviewed for renewal every five years in conjunction with the existing marine parks review process. We also believe that a sampling program to monitor the pipi population in NSW must use documented sampling protocols that are scientifically rigorous enough to assess natural variability and the impacts of overfishing, diseases, parasites and 4WD activities.
Econetwork – Port Stephens Inc. is a network of citizen groups promoting environmental sustainability and conservation. While our primary focus is on community and environmental issues in the Port Stephens region, we understand that these issues are often part of a much bigger problem.
We have grave concern for the status of pipi (Donax deltoides) stocks on the ocean beaches of New South Wales. The closure to commercial harvesting across the state you announced on 9 December to last only six months indicates that you are not convinced that our pipi stocks are in grave danger. Your concern seems to be based mainly on anecdotal information from recreational and commercial fishers, rather than on quantitative information in the 2008/2009 Status of Fisheries report from your Fisheries Department. This report assigned a status of “uncertain” to pipi stocks despite a long-term decreasing trend in the relative catch rate of the NSW commercial fishery throughout the period that catch statistics have been recorded for this species and a decline in total reported commercial catch “from more than 500 t in 2004/05 to less than 100 t in recent years”. The information in this report shows that the pipi population in New South Wales may be suffering from a significant decrease in the recruitment of juveniles.
The PhD thesis research and associated scientific publications by Dr. Sue Murray-Jones provide very useful population biology information for the species in New South Wales. Her paper in the journal, Marine Biology (1997, volume 128: pages 83-89), shows that larval dispersal and recruitment occur over large regional distances and is not restricted to individual beaches. Therefore, the fisheries in NSW operate on a single east coast pipi population. Her paper in the journal, Fisheries Research (2000, volume 44: pages 219-233), shows that the recreational fishery for this species is significant and accounted for almost 20 per cent of the total pipi harvest from Stockton Beach in the late 1990s. Based on this information and the fact that the commercial pipi harvest has remained very low during the last four years, we believe that a closure of the commercial fishery in NSW for six months will do very little to protect pipi stocks in NSW during the course of population assessment studies.
The longer term
All of the marine parks in New South Wales have ocean beaches that potentially support pipi spawning stocks. Very small areas of ocean beach within some of the marine parks, including the Port Stephens – Great Lakes Marine Park, are designated as sanctuary zones where pipis are protected. Now that your Fisheries Department is responsible for management of NSW marine parks, we respectfully recommend that you extend the closure of the commercial pipi fishery to two years and that you use your management authority to close all ocean beaches in all marine parks in NSW indefinitely to hand gathering of pipis by commercial and recreational fishers. This is completely consistent with the concept that marine parks provide sanctuaries for populations of marine species that may be threatened by human activities and would provide protection of pipi spawning and recruitment on a more suitable regional scale.
We are not aware of the experimental design and methodology of the pipi sampling program you are implementing but are concerned that an under-resourced research program based on non-scientific volunteers will not be rigorous enough to determine a definitive cause for the apparent decline in pipi stocks. Despite the assertion by some recreational fishers that this decline is a result of overfishing by the commercial sector, we believe that there are a number of possible causes. The sampling program must be rigorous enough to detect and assess these, including 1) natural variability in spawning and recruitment, 2) overfishing by a combination of the commercial and recreational fisheries, 3) outbreak of a disease or parasite and 4) mortality due to other human activities, such as unrestricted recreational driving of four wheel drive vehicles on our beaches and the use of 4WD vehicles as an integral part of the commercial and recreational pipi harvesting method. The PhD thesis by Murray-Jones (1999, University of Wollongong) and the supporting literature provide a number of examples of significant spatial and temporal variation in the populations of closely related surf clam species that have been linked to natural variation, overfishing and disease. More recent literature, such as Schlacher and Thompson (2007, Coastal Management, 35:567-583) flags the potential impacts of 4WD vehicles on intertidal invertebrates, including pipis, on the beaches of eastern Australia and calls for more detailed studies of individual species. Dr. Murray-Jones found small post-larval and juvenile pipis relatively high in the intertidal swash zone, indicating that they may be susceptible to crushing from 4WD activity.
The pipi sampling program should be based on protocols developed and recommended by James and Fairweather (1995, Marine and Freshwater Research, 46: 1093-9) and Murray-Jones (1999, University of Wollongong) to obtain suitable spatial replication. Sampling should be carried out independently of the commercial and recreational pipi fisheries by well-trained scientific staff. Along with standard morphometric data, samples should be retained for age, gonad, and pathology analysis. These stock assessment studies should be fully funded by commercial (NSW Estuary General Fishery and Commonwealth Fisheries Industry Research and Development Corporation) and recreational (NSW Recreational Fishing Trust) fisheries funding sources. Associated studies of 4WD impacts should be funded and conducted in association with a university. The entire sampling program should be carried out for at least two years on multiple beaches in each of the major coastal bioregions in New South Wales in order to obtain suitable temporal and spatial replication.
I am happy to discuss the above rationale further with you or your officers at any time.
Dr Bruce Pease