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Monitoring

HCRS Objectives

The current DAR marine monitoring program employs numerous different methodologies developed by DAR scientists in collaboration with NOAA, USGS and UH. Specific methods are used at study sites depending on the resource management concerns that DAR is looking to address, and include surveys of abundance of resource and herbivorous fish, smaller cryptic fish and recruits, urchins and larger mobile invertebrates, benthic habitat cover, coral health and biological diversity.

Monitoring Objectives

Routine marine monitoring has been a component of the Division of Aquatic Resources (DAR) (formerly the Department of Fish and Game) for over 50 years. Early efforts concentrated on using in-water visual assessments to measure resource fish stocks and changes to those stocks within marine protected areas and at artificial reef sites. For the past 15 - 20 years, efforts have been made to improve upon research methods, increase the frequency of surveys, expand the number of areas covered by assessments, and study changes associated with new management initiatives. As a result, today’s marine monitoring efforts are based on multi-faceted annual assessments of the coral reef ecosystem across a range of management zones.

The current DAR marine monitoring program employs numerous different methodologies developed by DAR scientists in collaboration with NOAA, USGS and UH. Specific methods are used at study sites depending on the resource management concerns that DAR is looking to address, and include surveys of abundance of resource and herbivorous fish, smaller cryptic fish and recruits, urchins and larger mobile invertebrates, benthic habitat cover, coral health and biological diversity. Advances in technology have also allowed for broader use of GPS and digital photography and allowed monitoring information to be analyzed and displayed in a GIS format. This report outlines a few specific examples of how DAR’s monitoring program has been utilized to guide and evaluate current resource management efforts.

 

Herbivore Management

Monitoring of coral reef habitats on Maui began as early as 1993 at some locations around the leeward coast. When compared with the results of current reef monitoring, these long-term data sets have allowed for the identification and quantification of alarming trends at nearly all monitored reefs. Many sites have experienced a complete collapse of the coral community, as live coral cover dropped dramatically and reefs became dominated by invasive algae.

The results of these monitoring efforts have been instrumental in helping the department identify a specific location were management action may help reverse the decline in reef habitat before it is too late. At the Kahekili reef monitoring sites in north Kā'anapali, Maui, coral cover was found to have declined from 55% in 1994 to 33% in 2006. This information, coupled with fish surveys suggesting reduced herbivorous fish abundance, helped guide the establishment of the Kahekili Herbivore Fisheries Management Area (KHFMA).

The rules at the KHFMA prevent take of critical grazing fish and sea urchins and became effective in July 2009. The implementation of these rules was the first time in Hawai'i that fisheries management was employed specifically to help protect coral reef habitat.  The creation of the KHFMA has also been critical in helping to increase public awareness of the many factors affecting our coral reefs and helping to drive land management policies towards reducing land-based pollution. Ongoing habitat and fish monitoring projects continue within this area in order to assess the effectiveness of the management efforts, and to guide future adaptive management.

 

Assessment of Laynet Fishing Regulations

One of the objectives of the fish and habitat monitoring programs on Maui and O'ahu is to study ecological trends in areas where laynet fishing has been prohibited since 2007. The primary monitoring sites and methodologies employed on Maui and O'ahu under the standardized DAR monitoring program were developed prior to the implementation of laynet fishing restrictions in 2007, so additional sites and survey methods were developed to address this new management initiative. To that end, we added components to our protocols to place greater emphasis on herbivorous fish and urchins and to detect changes in dominant coral and algal species.

On the Island of O'ahu, we are monitoring areas where laynet fishing was prohibited in relation to control sites where this fishing method is still permitted. One such area is Kāne'ohe Bay. Sixteen transect sites were established in the bay to cover fringing, barrier and patch reef habitats both inside and outside of the no laynetting zone. Sites were also selected in areas where the DAR Aquatic Invasive Species team is using urchins and the “Supersucker” to control invasive algae, and in the no fishing zone around Moku o Loe (Coconut Island). Research protocols were customized because of the unique habitat structure in Kane'ohe Bay, but include surveys of resource and herbivorous fish abundance and detailed benthic surveys to study trends in algal and coral cover. Additional survey sites have also been established to study ecological trends in shallow fringing reef habitats in areas such as Mamala, Hanauma, Waimanalo and Kailua Bays on O'ahu, and at seven sights on Maui. The Maui sites were selected and characterized based on the extent of past laynet fishing. Overall, these broadscale fish and habitat monitoring efforts should help evaluate the long-term effectiveness of the laynet fishing regulations.

 

The West Hawai'i Aquarium Project

In 1998, Act 306 resulted in the establishment of the West Hawai'i Regional Fisheries Management Area. Resulting management actions included the designation of 9 Fish Replenishment Areas (FRAs) where aquarium collecting was prohibited. Combined with existing marine reserves, this action set up a network of marine managed areas making aquarium collection illegal in 35.2% of the West Hawai'i coastline. In order to study the impacts of the FRA network, and of continuing aquarium fishing in areas remaining open to collectors, DAR and partner researchers from UH Hilo and Washington State University Vancouver initiated the West Hawai'i Aquarium Project (WHAP). Twenty-three permanent fish monitoring sites were established within representative locations at previously protected areas, newly established FRAs, and areas allowing for continued aquarium collection. Since their establishment in 1999, these sites have been routinely surveyed 4 – 6 times per year.

Over the ten-year period following the establishment of the 9 new FRAs, the size and value of the West Hawai'i aquarium fishery has increased substantially. There are more than twice as many active aquarium fishers and the value of the yellow tang fishery has increased by 72%. Even with the increase in fishing effort and overall harvest, WHAP monitoring data has provided unequivocal evidence of aquarium fish population recoveries within the FRAs. This evidence is particularly clear for the yellow tang fishery, which constitutes 82% of the total aquarium catch and 78% of the overall fishery value. Monitoring results have also demonstrated a clear increase of adult yellow tang reproductive stocks within the newly established FRAs and in unprotected sites near the FRAs. Because of this positive spillover effect, the 35% of protected area appears to sustain yellow tang breeding stocks in about 50% of the overall coastline. However, even with these positive FRA affects, open areas appear to be experiencing a decrease of yellow tang stocks to below baseline levels, suggesting that the current level of fishing is unsustainable. These monitoring results have been instrumental in evaluating the success of the overall FRA management approach, but more importantly they are helping to guide the West Hawai'i fisheries management council and the DAR as they adaptively manage this important fishery for future sustainability.

A summary of recent findings from DAR’s monitoring of coral reefs of the main Hawaiian Islands (NOAA Final Report, December 2010) follows:

 

O'ahu

  • Lay Net Restricted sites appear to have the highest fish biomass on average, and both these and MLCD sites have higher biomass than fully open areas. The MMA site had intermediate biomass, and was not clearly different from MLCD or open sites.
  • Lay Net Restricted areas compared favorably with MLCD and Open sites in species composition and biomass. A longer time series will be needed to determine if these areas are inherently healthier coral reef areas or are responding to the recent restrictions on the use of lay gill nets.
  • The surgeonfish family is by far the dominant fish family on O'ahu reefs by biomass, followed by triggerfish, goatfish, wrasse, and parrotfish families. 

 

Maui Benthic

  • Nine of the 20 currently monitored coral reefs have experienced significant changes with coral cover declining at 7 sites and increasing at 2 sites.
  • Coral cover declines at three sites (Honolua Bay, Mā'alaea Bay, and Papaula Point) were so severe that these individual reefs may have already experienced a total coral reef ecosystem collapse.
  • Sites experiencing significant coral reef declines appear to be affected by anthropogenic impacts such as land based pollution, sedimentation and overfishing.
  • Monitoring sites with stable high coral cover (Kanahena Bay, Olowalu, and Molokini) appear to be away from urban areas, are fairly remote or are located offshore.

 

Fish

  • Comparisons between fully protected reserves versus areas open to fishing show that marine reserves have consistently higher resource fish biomass levels, larger sized fish, greater numbers of apex predators, and the greater abundances of schooling grazers. Shallow Water Habitat and Fish Surveys (lay-net regulation assessment surveys)
  • Fish biomass levels were higher in areas where past lay-net fishing effort was lower.
  • Qualitative habitat assessments show the areas that experienced the highest past lay-net fishing effort had the most degraded reef habitats with algal cover at 20%.

 

Herbivore Grazing Assessments

  • General grazing trends for both acanthurids and scarids were similar. A significant negative correlation for grazing rate versus fish size was observed. Conversely, bite sizes increased with fish size.
  • The area of algae scraped by scarids over a year has a significant positive linear relationship to size (i.e. larger fish have a greater impact on algal removal).
  • Both scarids and acanthurids are critical grazers for controlling algae on the reefs. Not enough data was gathered on kyphosids to assess their importance due to infrequent presence of this family in the study sites.

 

Roi Control Assessments

  • When data on both CPUE and the number of roi escaped are combined, a significant decline in roi abundance can be seen.
  • While roi have been substantially reduced, they are still present in moderate densities despite months of removal effort.
  • Ciguatera analysis of fish weighing over one pound indicates that 69% of the population contains ciguatoxin.

 

Coral Disease Assessments

  • Data showed a 47% decrease in coral cover over a period of one year at a site known as Montipora Pond, wherein a nearly monotypic stand of Montipora capitata has a chronic outbreak of Montipora white syndrome.

 

Hawai'i Benthic Coral and Habitat Surveys

  • Total Coral cover declined significantly at 6 northern sites in West Hawai`i between 2003 and 2007. A strong winter storm in 2004 was likely responsible for the declines, but a major sediment event in 2006 may also have affected sites at Kamilo Gulch and Waiaka'ilio Bay on the North Kohala coast.
  • No invasive alien algal or coral species were detected at any site. Macroalgal cover was very low at all sites.
  • The distribution of the octocoral Sarcothelia edmonsoni around developed areas near Kona and its virtual absence around undeveloped shoreline areas suggests possible anthropogenic (pollution) influence. Since other studies have cited octocoral as a pollution indicator and shoreline development in West Hawai'i is expected to continue to increase, further studies should be undertaken to determine the relationship between octocoral presence and land based pollution.

 

Coral Disease Surveys

  • The following coral diseases were recorded at West Hawai'i monitoring sites in 2010: Porites growth anomaly, Porites tissue loss syndrome, Porites multifocal tissue loss, Porites trematodiasis, Montipora growth anomaly, Pavona varians hypermycosis, Pocillopora tissue loss.
  • Porites spp. were the most susceptible to disease with the most widespread diseases including growth anomalies, trematodiasis, and tissue loss syndrome of Porites spp.
  • Overall disease prevalence and prevalence of Porites growth anomalies were positively correlated with total estimated size and number of submarine groundwater (SGD) “plumes”.
  • West Hawai'i sites show a significant negative relationship between disease prevalence and distance from harbors/boat ramps, particularly for Porites growth anomalies and Porites tissue loss syndrome.
  • No significant changes in disease densities were found between survey years 2007 and 2010 for ten DAR monitoring sites. However, cases of Porites growth anomalies and Porites tissue loss syndrome slightly increased at four sites located in close proximity to harbors/boat ramps.
  • No statistically significant relationships were found between prevalence of coral diseases and abundances of corallivorous butterflyfishes and parrotfishes for West Hawai'i’s reefs.

 

Fish

  • The abundance of both aquarium and food fishes increased significantly in West Hawai'i over the last 11 years. The overall number of fishes not substantially harvested for either food or for the aquarium trade did not change significantly, although individual species within this group may have.
  • Examination of the temporal trends of some of the most common reef fish families indicates that acanthurids have been increasing over the past eleven years while labrids have decreased. Overall, chaetodontids and pomacentrids have been relatively stable, although some species within the family have either increased or declined.

 

Introduced Species/Fish Die-Off

  •  Transect data reflects overall low abundance of ta'ape in the reef areas of the study sites and they are rarely found in the shallower water where resource fish surveys are conducted. Ta'ape are numerous in some locales, usually along drop-offs and deeper reef areas, but their distribution is highly patchy and they are not at all abundant in many reef areas in West Hawai'i. Ta'ape numbers also appear to have declined from earlier periods.
  • There has been a marked decrease in roi abundance both on West Hawai'i transect (56% decrease) and free swim surveys (55% decrease). This decline may be related in part to an unusual fish die-off in West Hawai'i which first became apparent in May 2006.
  • Early in 2010 a die-off of large puffers, with external symptoms quite similar to the previous mortalities, began to occur on Maui and Hawai'i Island. Over the ensuing months low numbers of dead and dying puffers were progressively reported up the island chain as far as Kaua'i (Oct. 2010).
  • West Hawai'i monitoring data indicates a substantial decline has occurred in the abundance of the Hawaiian spotted toby (Canthigaster jactator) and the spotted puffer (Arothron meleagris) with a precipitous drop of the latter species in 2009/2010.
  • As of November 2010 a total of 106 puffers have undergone both gross and microscopic examination. All assays for viruses (including electron microscopy) have so far come up negative and all attempts to incriminate any infectious agent as a cause have come to naught.
  • An examination of roi and two of the most abundant species in roi’s prime habitat, the yellow tang (Zebrasoma flavescens) and kole (Ctenochaetus strigosus), fails to indicate direct negative impact on either species.
  • Examination of the relationship between roi abundance and the abundance of various species and functional groups shows no significant negative relationships. In other words having more roi in an area does not result in having less total fish, small prey fish, other piscivores, yellow tang Young-of-Year (YOY), kole YOY or all YOY.
  • The estimated roi population in West Hawai'i in the 30’-60’ depth range (hard bottom only) is 58,839 individuals.

 

Aquarium Species

  • Ten years after closure of the FRAs, the top 20 aquarium species showed a small overall increase in abundance across all sites (open, FMA, MLCD) relative to the period before the FRAs were operational. Most of the increase was attributed to the top two species, yellow tang and goldring surgeonfish (kole), which comprise 91% of the West Hawai'i aquarium catch.
  • Seven of the top 10 most collected species (representing <6% of all collected fish) decreased in overall density across all sites. Three of these decreases were significant (Achilles tang, multiband butterflyfish and black surgeonfish).
  • The FRAs were ‘effective’ (increases in FRAs relative to long-term MPAs) for eight of the top 10 collected species with three being statistically significant. With only a single exception the FRAs were highly effective in increasing the abundance of yellow tang along the West Hawai'i coastline.
  • A decrease of yellow tang in open areas to below baseline levels is largely attributable to an increase in the number of aquarium collectors and collected animals relative to the period when the FRAs were established. Kole are more abundant and much less collected than the yellow tang and populations in open areas have remained relatively stable. Achilles tang show a declining trend.
  • Concerns over continued expansion of the aquarium fishery and harvesting effects in the open areas has prompted DAR and the West Hawai'i Fisheries Council (WHFC) to develop a ‘white list’ of 40 species which can be taken by aquarium fishers. All other species are off limits.
  • Based on an analysis of the differences in density between open and protected areas, there was clear evidence of an aquarium collecting impact for only 5 of the 33 white list species analyzed. Four of the 5 are among the 10 most heavily collected species. For the others, it appears that inclusion on the white list poses little or no threat to their populations.
  • Based on a comparison of reported catch and estimated population abundance in the 30’-60’ depth range, aquarium collecting is having a major impact on Achilles and yellow tang, with aquarium fishing mortalities reaching 80% and 60% respectively. Achilles tang has had low levels of recruitment over the past decade and substantial numbers of larger fish (i.e. ‘breeders’) are taken for human consumption. Yellow tang have generally recruited reliably but the numbers of collectors and aquarium take has risen substantially over the past decade.
  • For most of the species on the white list, collecting impact, in terms of the % of the population being removed annually, is relatively low with 10 species having single digit % catch and 18 species having % catch values <1%.
  • Eight no lay gill netting areas were established in West Hawai'i in 2005, comprising 25% of the coastline (including already protected areas). Nearshore monitoring results did not find major differences in food fish abundance in/out of the no lay gill netting areas. The lack of a marked effect of protection may be due to several factors, including the relatively low number of lay gill nets that are presently being used (i.e. registered) in West Hawai'i.

 

Invertebrates

  • Crown-of-thorns starfish have a low absolute abundance on West Hawai'i reefs and there has been an overall decreasing trend in abundance over the last four years.
  • Three species of monitored urchins have been increasing on West Hawai'i reefs with the collector urchin (T. gratilla) exhibiting the greatest increase.