Bottomfish Fishery
Introduction
The commercial bottomfish stocks in the Hawaiian Islands are divided into two fisheries: seamount groundfish and deep-slope bottomfish. The seamount fishery targets alfonsin and armorhead. The only area in the U.S. EEZ for this fishery is Southeast Hancock Seamount located 1,400 nmi northwest of Honolulu. This trawl fishery was started by the Russians and Japanese in the late 1960s and large catches were made for about 10 years until overfishing caused a collapse in the fishery. This fishery has never been domestically harvested. A moratorium on fishing within the U.S. EEZ began in 1986 and continues through the present as no substantial recovery in the fishery has been observed.
The deep-slope bottomfish fishery in Hawaii concentrates on species of eteline snappers, carangids, and a single species of grouper concentrated at depths of 30 -150 fathoms. These fish have been caught for subsistence since ancient times and commercially for at least 90 years. The deep-slope fishing grounds within the US EEZ are divided into three management zones. The inhabited Main Hawaiian Islands (MHI) support numerous subsistence, recreational, and commercial fishermen with considerable overlap by category. The uninhabited Northwestern Hawaiian Islands (NWHI) are divided into the Mau Zone, closer to the MHI, and the Hoomalu Zone. Fishing in these zones is conducted solely by commercial fishermen and requires Federal licensing. The Ho'omalu Zone is a limited-entry zone.
Vessel size varies considerably with larger, fully commercial vessels (30 ft long and larger) conducting trips of about 10 days, and smaller vessels (<30 ft) generally restricted to the MHI and to trips of 1-3 days. Most vessels in this fishery are fully outfitted with electronic navigation and fish-finding equipment, as well as with electric or hydraulic line-hauling equipment. The catch is sold fresh in the round for local consumption.
Catch and revenue data for bottomfish have been collected by the State of Hawaii Division of Aquatic Resources (HDAR) since 1948 in the form of a report submitted by commercial fishermen. No data are collected for recreational or subsistence fishermen for either the NWHI or the MHI. There is very little recreational or subsistence fishing in the NWHI, and catch in the MHI is estimated to be about equal to the commercial catch.
Available NWHI revenue data are not separated by zone. Overall NWHI inflation-adjusted revenue has been relatively stable since 1990. Inflation-adjusted average bottomfish price appears to be relatively stable in recent years.
Seamount Groundfish - Hancock Seamount
No fishing has been allowed on the armorhead stocks of the southeast Hancock Seamount since a moratorium began in August 1986.
Armorhead stocks outside of the U.S. EEZ experienced a short pulse in recruitment in 1992 that did not carry over to 1993. The 1993 SPR values at Southeast Hancock Seamount, calculated from research longline catches, were more than double that of the last assessment in 1991 and nearly as high as the highest CPUE recorded since surveying began in 1985. Even at 2.0%, or 10% of the threshold level for recruitment overfishing of 0.20, they still indicate a collapsed fishery. About 99% of the known armorhead seamount habitat occurs outside the EEZ, an area which had 0.06 SPR in 1993.
Data for Hancock Seamount have not been available in 1994, and no research cruise occurred in 1994 or 1995. The data outside the EEZ have been unavailable since 1998. SPR values obtained at Colahan Seamount have been shown to correlate well with values from the Hancock Seamount and can be used as proxies. The 1997 SPR for Colahan Seamount was 1.1%, indicating a collapsed fishery. As a result, data have been unavailable for Colahan Seamount since 1997.
Deepslope Bottomfish - Hoomalu Zone
From 1988 to 2001 an average of 6 vessels bottomfished in the Hoomalu Zone landing an average of 243,000 pounds of fish per year with a value of $753.000 and an average catch per trip of 6,300 pounds.
The NMFS Hoomalu Zone bottomfish CPUE has been on a downward trend since 1988, reaching its lowest point in 1994. The HDAR Hoomalu Zone bottomfish CPUE followed an increasing trend, but dropped sharply in 1994 for unclear reasons and rose by 20% in 1995. The 5,543 lb/trip value for 1995 was 66% of the 8,440 lb/trip average of the first 3 years from 1948 to 1950, indicating that bottomfish stocks in the Hoomalu Zone appear to remain relatively healthy. Analysis of SPR and percent immature in the catch shows no problems to date
Mean weights of fish in the Hoomalu Zone continued to exhibit year-to-year fluctuations, but are still at much higher values than MHI mean weights. The percent of immature fish in the 1995 catch was still safely under 50% for all species evaluated.
The SPR values in the Hoomalu Zone increased in 1995, with four of the five measured species showing values of 0.77, while onaga had an SPR value of 0.56.
Deepslope Bottomfish - Mau Zone
From 1988 to 2001 an average of 9 vessels bottomfished in the Mau Zone, landing an average of 109,000 pounds of fish per year with a value of $319.000 and an average catch-per-trip of 1,900 pounds.
The NMFS bottomfish CPUE data have only been available for the NWHI fishery as a whole since 1984 and by Hoomalu and Mau Zone since 1988. The NMFS NWHI bottomfish CPUE steadily decreased from 1987 to 1992, rose in 1993, and then dropped to an all-time low of 472 lb/day in 1994. This is 64% of the 739 lb/day average of the first 3 years from 1984 to 1986 and 42% of the original level, which is a yellow-light condition. This could be the result of a return to normal abundance, rather than a decrease in normal fish abundance, but it could also represent declines in some stocks. The reasons are currently unclear.
The NMFS Mau Zone bottomfish CPUE had been steadily decreasing since 1989, but increased 44% in 1994 to 385 lb/day, for reasons unknown.The HDAR Mau Zone bottomfish CPUE decreased 34% from 1994, with the 1995 value only 42% of the 5,911 lb/trip average of the first 3 years from 1948 to 1950. This indicates a yellow-light condition.
Nonparametric 95% confidence intervals were calculated for HDAR CPUEs by the "bootstrapping" method. Mean weights of fish in the Mau Zone continue to exhibit year-to-year fluctuations but are generally at much higher values than MHI mean weights. The percent of immature fish in the 1993 Mau Zone catch was still safely under 50% for all species evaluated.
The SPR values in the Mau Zone had been decreasing since 1990 (mirroring the pattern in the HDAR CPUE) but experienced a surprising rise in 1994 and a return to lower levels in 1995. All values are presently above 0.42, well above the critical level of 0.20. SPR values are higher in the NWHI than the MHI because most of the catch is mature fish. SPR values in both NWHI zones have never fallen below 0.35.
Deepslope Bottomfish - Main Hawaiian Islands
From 1986 to 2001 an average of 9 vessels bottomfished in the MHI landing an average of 594,000 pounds of fish per year with a value of $1,920,000 and an average catch-per-trip of 219 pounds.
In 1988, there was a dramatic increase in MHI bottomfish landings because of a bonanza uku or gray snapper harvest. Since that time there has been a steady decline in total landings, which stabilized during 1990-92. Landings in 1994 rose 32% over 1993, which was the lowest recorded annual value, and then dropped slightly in 1995. The slight decrease in MHI landings for 1995 occurred despite a 16% increase in effort resulting in the lowest CPUE ever.
Recent CPUE values are less than one-third of the early baseline values, signifying a yellow-light condition in the MHI. This indicator suggests that ehu is the most stressed species with a recent CPUE of only 11% of the initial years of the fishery. The increase in the late 1980s MHI CPUE was primarily due to a large increase in uku catches and may not indicate an increased abundance in other species.
Total ex-vessel revenue from the MHI showed a general decline during 1988-1995 caused mainly by decreased landings but inflation-adjusted average price appears to be relatively stable in recent years.
Most of the more commercially important species in the MHI have had relatively stable mean weights since 1984. Hapuupuu's mean weight that dropped sharply in 1993 rose in 1994, then dropped more in 1995. It is the only species that shows a recent decline in mean weight; however, it should be noted that the sample size was small (only 2.5% of the catch). MHI onaga again had the highest percentage of immature fish and was the only species where over 50% of the catch was consistently immature, signifying a yellow-light condition.
For the third year, 95% confidence intervals were constructed based on "best" and "worst" case bounds of SPR components of CPUE and percent immature. For the first time we calculated SPR values using both aggregate CPUE, as in previous years, and targeted CPUE, which we feel gives a more accurate picture for individual species.
Stocks of many of the BMUS species in this zone are stressed. Each of the BMUS species evaluated have a yellow-light condition due to a drop in CPUE below 50% of original values.
Of the five major species for which the SPR indicator was calculated using aggregate CPUE, onaga, opakapaka, and hapuupuu stocks are recruitment overfished since they had values below the 0.20 "critical" level. Uku and ehu showed SPR values of 0.23 and 0.24, respectively, approaching this level. The aggregate CPUE for hapuupuu dropped to 0.20 for the first year and must also be considered in a red-light condition.
The use of targeted CPUE showed a different picture for the four species where targeted trips are available. Here, onaga and ehu SPR's of 0.06 and 0.07, respectively, are much worse than indicated using aggregate CPUE. These levels are red-light conditions demanding immediate action. Targeted SPR values for opakapaka and uku of 0.31 and 0.39 respectively are much higher than previously indicated. Onaga's SPR has now been below 0.20 for the past 7 years and ehu for the last 10 years, using targeted CPUE, indicating a red-light situation for these species.