The November Hilo Bay Watershed General Meeting occurred on November 10, 2008 at Mokupapapa Discovery Center.  Dr. Robert T. Nishimoto presented his study, “Mugilids in the Muliwai: linking mauka to makai.” The study analyzed the status of the Hawaiian mullet or mugil cephalus, particularly the causes of this mullet’s decline and what has been attempted to restore its numbers.  Nishimoto summed up his agency’s efforts at this by stating, “Many people ask, brah where’s the fish, so we try to work on that.”  

According to Nishimoto much of the decline of the Hawaiian mullet relates to a lack of understanding of how the aquatic systems work.  “Systems are resilient, but if we don’t give them a chance they have difficulty bouncing back.  People often talk about the birds, ocean, or the mountains.  Where the oceans and the mountains meet is often ignored, which brings to mind places like Chesapeake Bay and San Francisco Bay, which are great estuaries.  Many coastal marine species use estuaries as nursery habitat,” he said.  This relates to the mullet because mullet move between the ocean and estuaries during their different life stages.  

Aquaculture also has affected the well-being of the Hawaiian mullet.  The history of Hawaii includes various game fish, like tilapia, being brought in to increase the amount of fish that could be caught by anglers.  Fisheries in the 1900s started with three commercial species and then aquaculture began with mullet being raised in 1907.  “Aquaculture was considered the blue revolution, [but] was a sort of false hope,” Nishimoto stated on this subject.

Fisheries continued to decline up to present day.  The coastal fishery of Hilo Bay had declined by 80 percent in 1987.

Mullet is an important species to the Hawaiians.  Nishimoto stated that one example of this was the legend of Makoa, in which Makoa sent a message of peace and mullet to another group of Hawaiian people.  The Hawaiians also have words like  pua or pua’ama for fingerling or five cm, kahala for hand length or 15 cm, and ’ama’ama for larger fish, which he thought reflected their understanding of fish lifecycles and valuing of this resource.

These issues led Nishimoto and other researchers to study ways to raise the fishery size to its former abundance. This study was a joint program and effort by the Division of Aquatic Resources and Oceanic Institute from 1990 to 1995.  The unhealthy conditions he and his group noticed in the local estuaries were a lack of vegetation on the banks of the rivers, hypoxic water conditions from changes in the watershed system, many introduced fish species, and groundwater plume intrusions.  The solutions Nishimoto’s team came up with to increase mullet abundance ended up being an increase in recruitment through releasing artificially propagated fish stock, fishery regulations, restoration of the estuarine habitat, identification of the possible threat provided by alien species, and documentation of the estuary’s status.  Other projects in the study included putting wire tags on hatchery fish to track them and putting up signs warning fishermen about new fishing regulations.  

The results of the fishery recruitment program were that the hatchery contribution was 67 percent.  The biologists were concerned, though, that these hatchery fish could be competing with wild fish. Also, it was discovered that hatchery releases stayed in the estuary for three to four years.  Due to this concern they stopped the stocking program in the year 2000. “Stock needs to be in conjunction with management,” Nishimoto stated in regards to what they learned from this stock recruitment research.  

The biologists restored riparian cover in their efforts to restore the estuarine habitat.  Riparian cover is shoreline vegetation and shady water areas.  This restoration effort used native aquatic plants and removed alien species.  The original shoreline plant cover was 25 non-native species.  Fishermen ended up complaining about this cover blocking their ability to land lines.  These complaints then led Nishimoto’s team to create parameters in the riparian cover, which the local ducks seemed to enjoy.  The restoration efforts had the results of 75 percent of the fish species caught by fishermen, being native species.

The research team discovered that the alien fish species, Australian or summer mullet, was having a possible impact on the amount of the native Hawaiian mullet.  Australian mullet is also known as valamugil engeli in the scientific system.  A 2006 study, by this team, discerned a trend of higher overall Australian than Hawaiian mullet, in the estuaries.  Secondly, the Australian mullet has a larger dietary preference than the Hawaiian, but both eat diatoms.  Lastly, the Australian mullet can take advantage of a wider range of habitat conditions.

The status of the estuarine habitat is that of potentially degraded.  The discovery of frequent dinoflagellate blooms were linked, by the researchers, to the ruining of habitat and a higher level of nutrients.  Blooms are often associated with lower oxygen conditions.

The tag initiative had the problem of residents wanting the whole fish.  This was a dilemma because Nishimoto’s group needed the heads, so that they could extract the tags from the heads, since this is where this particular tagging method needed to place the tags.  Their solution was to have his staff hang out at cleaning stations and then stick the fish heads through a magnetic reader.  This solution had a limited amount of success, but required the compliance of fishermen.  

Cleaning stations were installed at the mouth of Hilo Bay near Suisan fish market, the right side of Waiakea Pond near Wailoa River, the middle of Hilo Bay, and the left side of Hilo Bay near the hotels.  

Compliance was also an issue with the regulation signs.  The people who fished there complained to Nishimoto’s crew that the signs were getting in the way of their fishing lines.  

Nishimoto concluded his presentation with some closing comments and responsed to questions from the audience.  

This ending discussion centered on the future and past of estuarine restoration projects.  Nishimoto talked about how earlier plant restoration work had been done in the Hawaiian Islands, before this estuary restoration work, because the government wanted to create habitat for migratory birds.  An audience member commented on this, “So birds got habitat, but the fish didn’t.”  Audience members also commented about the need to incorporate traditional management practices into how our natural resources are managed and that we should engage local people in counting fish.  

Nishimoto stated, in regards to the future, that he hopes that estuaries will be designated as protected areas before he retires and that he has hope along with worries about it.  “Is there hope, yes there is hope.  The more I am in this profession the [more] worried I get because it is a global issue,” he said.  Nishimoto also challenged the audience with the question, “What does a park mean to you, is it green and beautiful or functional?”