Long Term Ecological Studies and Marine ProtectionAn ongoing challenge to marine science is to design and carryout research and observations over long time periods. There are many reasons why this is important and valuable. A major reason is that is always hard in the marine environment to determine the difference between the effect of a short term localised impact like fishing has on species and habitats verses change that is the result of natural variation brought about by changes in the environment like current, water temperatures or climate change. One way to approach this is to carry out long term studies. In this section we highlight two significant studies of this kind. They are very rare and tell us a great deal about small changes that over time which can have very significant effects on species and marine systems.
Long-term trends in lobster populations in a partially protected vs. no-take Marine Park
Nick T. Shears,, Roger V. Grace, Natalie R. Usmara, Vince Kerr, Russell C. Babcock,
Increasing the level of protection afforded to the marine environment requires assessment
of the efficacy of existing marine protected areas (MPAs) in protecting exploited species.
Long-term data from before and after the establishment of MPAs provide a rare but valuable
opportunity to assess these effects. In this study we present long-term data (1977–
2005) from before and after park establishment, on the abundance of spiny lobster Jasus
edwardsii from fixed sites in a no-take marine park and a recreationally fished marine park,
to assess the efficacy of no-take vs. partial protection. Lobster densities were comparable
between both marine parks prior to park establishment, but the response of lobster populations
differed markedly following protection. On average, legal-sized lobster were eleven
times more abundant and biomass 25 times higher in the no-take marine park following
park establishment, while in the partially protected marine park there has been no significant
change in lobster numbers. Furthermore, no difference was found in densities of
legal-sized lobster between the partially protected marine park and nearby fully-fished
sites (<1 per 500m2). Long-term data from fully fished and partially protected sites suggest
long-term declines in lobster populations and reflect regional patterns in catch per unit
effort estimates for the fishery. The long-term patterns presented provide an unequivocal
example of the recovery of lobster populations in no-take MPAs, but clearly demonstrate
that allowing recreational fishing in MPAs has little benefit to populations of exploited species
such as J. edwardsii.
Fish Populations in a Tidal Estuary in the Marlborough Sounds, New Zealand from 1971 to 2004
Bray,J.R.; Struik ,G.
Fish netted in a tidal New Zealand estuary from 1971 to 2004 declined between 1971-74 and 2001-04 by 46% in percent occupied tides, 70% in number per tide, 71% in weight per fish, 91% in weight per tide, 48% in length per fish and 85% in length per tide. There was a shift from Early to Mid Dominant species followed by fluctuation between Later Dominants and, briefly, Invaders. Degree of interspecific association was significantly dependent on food preference, a seasonal variable and level of intraspecific association. Spring precipitation was positively related to increases in fish weight and length, followed in the next year by increases in number, weight and length per tide.