Management methods for a sea urchin dive fishery with individual fishing zones.
KEY WORDS: fishery management, green sea urchin, Strongylocentrotus
Some usual sea urchin stock assessment methods are not practical for the Nova Scotia sea urchin fishery. Diver surveys of biomass are expensive and the harvestable portion difficult to measure. Nutritional state and seasonal cycle affecting gonad size (Himmelman 1978) and hence sea urchin marketability vary on small spatial and temporal scales (Keats et al. 1984). Urchins of identical size and appearance are valued at Can $0 to $4 per kg depending on gonad quality. The width of the area to be included in the harvestable biomass is unknown because urchins form a slow-moving belt from deep water to the edge of macrophyte beds where harvesting takes place. This was shown by fishers' records reporting six or more harvests from the same location in 3-y (Miller & Nolan 2000). Predicting recruitment to legal size is difficult because growth rate and size at age vary on small spatial scales (Sivertsen & Hopkins 1995, Robinson & MacIntyre 1997, Vadas et al. 2002, Brady & Scheibling 2006). Variability within each of these important population parameters makes it impractical for a management agency to monitor a stock over a large area. Unknown stock-recruit relationships preclude making an informed choice of spawning stock biomass.
The purpose of this report is to describe methods and rationales of assessment and management for a Nova Scotia fishery for the green sea urchin (Strongylocentrotus droebachiensis Muller). The approach attempted to follow the principles of "mechanism design" (Anon 2007) where the rules are designed so that the desired outcome is achieved by participants pursuing their self interests. Important components were fishers managing individual zones on a micro spatial scale, maximizing harvest revenue from the existing stock size, adopting a reference point that fishers and the government management agency could use to measure stock management success, and few regulations.
The Nova Scotia sea urchin resource is well suited to area-based management. The green sea urchin and its principal macroalgal food, Laminaria sp., are abundant (Wharton & Mann 1981, Miller 1985, Scheibling 1986) but not optimally distributed for high fishery yield. Much of the sea urchin stock is of no commercial value because the sea urchins are poorly fed and the gonads poorly developed (Fletcher et al. 1974, Keats et al. 1984, Meidel & Scheibling 1998, Wahle & Peckham 1999). In laboratory trials many authors have demonstrated differences in gonad size in response to food quantity and quality (e.g., Vadas 1977, Himmelman 1984, Lemire & Himmelman 1996, Hooper et al. 1997). The low motility of sea urchins (Garnick 1978, Scheibling et al. 1999, Dumont et al. 2004) and macroalgae make them well suited for manipulation. Also, as a dive fishery, the results of harvesting and enhancement are visible to the fisher, unlike most fisheries where perceptions of the state of the stock are clouded by selectivity of the fishing gear.
Community based and comanagement of sea urchin fisheries has been practiced elsewhere. Japanese communities have had tenure over coastal resources, including sea urchins, for at least a century (Ruddle 1989). Serial depletion of stocks by the world's largest sea urchin fishery in Chile prompted the implementation of two management approaches (Moreno et al. 2007). Communities of fishers were given exclusive access to their coastal resources if they make 6-mo resource projections that the government could use to set catch quotas. The second plan, implemented on a pilot scale, includes rotational harvests and reproductive reserves. In Baja California the Mexican government has given exclusive area access to both groups and individuals and limits divers to 150 kg/day and fishing to 5-days/week (Andrew et al. 2002).
The Nova Scotia Fishery
The Nova Scotia fishery is located on the outer coast from Shelburne to Cape Breton Counties and in Digby County at the mouth of the Bay of Fundy (Fig. 1). This is an autumn-winter dive fishery with the market almost entirely in Japan. Although called a roe fishery, gonads of both sexes are sold.
Disease decimated most of the stock in the early 1980s (Miller 1985) before the fishery began and again from 1995 to 2001 (Scheibling & Hennigar 1997, Miller & Nolan 2000, sea urchin fishermen, pers. comm.). Landings decreased from a peak of 1,300 mt in 1998/99 to 255 mt in 2005/06 (Fig. 2) reflecting the loss of stock to disease.
[FIGURE 1 OMITTED]
Most of the fishery is managed by an area-based regimen where individual fishers have exclusive access to a fishing zone and are given responsibility to manage the stock in their zone. Legal authority for individual zones is found in the Canada Fisheries Act where many types of management areas are used to regulate catch and fishing locations. Sea urchin areas were an extension of this provision. The conditions associated with a fisher receiving an individual zone were (1) previously harvesting at least 25 mt/yr; (2) harvesting sea urchins from only one zone, (3) enhancing the yield potential of the stock in the zone; (4) exclusive access to the zone for a trial period of 4-y if enhancement was carried out; (5) providing details of fishing location and catch; (6) mapping sea urchin and macrophyte distribution within the zone; and (7) at the end of the trial period paying for a zone audit that measured management performance. The individual zone licenses had no seasons or catch quotas and applied only to sea urchins.
[FIGURE 2 OMITTED]
Five fishers in Digby County chose to fish competitively, because they could not agree on the division of preferred areas. For these areas they first chose a shorter fishing season and later a number of fishing days each boat was allowed to fish within a longer season.
For effort limitation and diver safety a boat (license) was limited to four divers. The minimum legal size was 50 mm test diameter, well above the size of maturity of 15-20 mm (Miller & Mann 1973, Meidel & Scheibling 1998). Undersized urchins were discarded on the fishing ground rather than at the wharf or on land.
Kelp-Sea Urchin Cycle
In Nova Scotia sea urchins and macroalgal abundance vary through a natural cycle (Scheibling 1984, Miller 1985, Johnson & Mann 1988, Chapman & Johnson 1990), but in only part of the cycle are the urchins well fed and at a suitable depth for diver harvest. Figure 3 is a new version of this cycle.
In stage 1 the absence of sea urchin grazing kelp species dominate stable rock surfaces from the deep edge of the intertidal to a depth of 12-20 m (Edelstein et al. 1969, Mann 1972, Miller 1985).
In stage 2 dense sea urchin feeding fronts form. Urchins which settle out of the plankton into kelp beds can become abundant enough to eat holes in the bed and the holes coalesce into feeding fronts (Mann 1977), but more commonly larger sea urchins move from deep water to form feeding fronts at the deep edge. Dense feeding fronts of the green sea urchin have been reported for Nova Scotia (Breen & Mann 1976, Brady & Scheibling 2006), Newfoundland (Himmelman 1984), Quebec (Himmelman 1991), Maine (Wahle & Peckham 1999), New Hampshire (Whitman 1985), British Columbia (Foreman 1977) and in a more diffuse form in Iceland (Hjorleifsson et al. 1995), and Norway (Hagen 1983).
In stage 3 kelp beds recede as urchin feeding fronts progress up-slope towards shore. This has been documented many times as reviewed by Leinaas and Christie (1996). Urchin density of about 2 kg/[m.sup.2] is sufficient to advance the front (Breen & Mann 1976, Scheibling et al. 1999) and trailing urchins of only 150-500 g/[m.sup.2] can maintain the bottom clear of macrophytes (Breen & Mann 1976, Chapman 1981, Bernstein et al. 1981).
[FIGURE 3 OMITTED]
In Stage 4 kelp beds are reduced to refuges protected from urchin grazing. These include areas with large wave surge, or with slight water motion, or with low salinity (Himmelman & Lavergne 1985). However, these areas may occupy no more than 10% of the habitat suitable for kelp in the absence of sea urchins (Miller 1985).
Mass mortalities caused by an ameboid pathogen (Jones 1985) can reset the cycle to Stage 1 from any of Stages 2, 3, or 4 (Fig. 3). During 1980-1985 the effect extended along 380 km straight line distance and killed 270,000 mt (Moore et al. 1986). The 1990s occurrence spanned 450 km and killed 10-100 times more sea urchins than were taken during 7 y of the fishery (Miller & Nolan 2000). Sea urchin grazing has been documented many times as the agent that denudes large areas of stable rock substrate suitable for macrophytes (reviewed by Keats 1991, Leinaas & Christie 1996) and the pathogen as the agent that resets the cycle to stage 1 (Miller 1985, Johnson & Mann 1986).
Maintaining the kelp-sea urchin cycle at stage 3 or reversing it from stage 4 to stage 3 is a principal objective of the Nova Scotia sea urchin fishery management plan. At this stage the feeding front, where most of the harvesting is carried out, is shallow enough to be within diving depth and the kelp bed is wide enough not to be at risk of being eliminated by sea urchin grazing. Whereas the cycle can remain in stage 1 (Sharp 1980) or stage 4 (Miller 1985) for decades, keeping it at stage 3 or moving it from stage 4-3 requires active management by adding or removing algae or sea urchins. Several authors have demonstrated experimentally that removal of green sea urchins allows rapid regrowth of macroalgae (Chapman 1981, Himmelman et al. 1983, Keats et al. 1990, Leinaas and Christie 1996). Allowing the urchins to keep part of the bottom grazed free of macroalgae probably improves recruitment of juveniles to the population (Keats et al. 1984, Raymond & Scheibling 1987).
In this paper enhancement means manipulating the resource and its food to obtain more biological and economic yield than would occur by a more typical hunting-gathering approach.
Exclusive harvesting rights for an area allowed a fisher to individually benefit from good resource husbandry and be identified for poor husbandry. Although more quantitative reporting would have been preferred, based on close working relationships between the fishers who carried out enhancement we judge their reports to be creditable. Their enhancement included moving kelp to overcrowded and underfed urchins, moving urchins to kelp, and adjusting harvesting intensity to maintain the feeding front at an acceptable depth.
Surveys were for the most part one-dimensional measurements of the lengths of sea urchin feeding fronts. Lengths were measured from nautical charts marked at sea or by using a GPS at sea. Working from an outboard powered skiff fronts were located by looking for a line of sharp contrast between the dark kelp and light colored rock bottom. Once located the boat driver simply steered along the front, when necessary observing through a glass-bottomed viewer to eliminate surface glare. When not visible from the surface the front could usually be located using a color sounder. Occasionally a diver was deployed to swim the front, while towing a buoy that was tracked by the skiff. The skiff had the advantages of fast travel, maneuverability to operate on wave-exposed rocky shores in as little as 1-m depth, and low freeboard for viewing the bottom and diver support.
Field surveys became more quantitative to meet evolving data needs (Table 1). The lengths of shore referred to are the stable rocky subtidal, including the circumference of islands and shoals. The original method for assessing harvest potential for individual zones requested by fishermen (1) was to search for feeding fronts every few km of shore, following the fronts for a few hundred meters noting if the sea urchins were of commercial size. A more exact measure adopted later (2) was to measure the length of all feeding fronts in less than 13 m depth. To establish annual yields per m of feeding front (3), a diver measured the length of several fronts by laying out metered string while swimming. For these fronts we had annual harvest records for 2-3 y after omitting the first harvest year to avoid virgin densities. To audit the degree of harvester utilization of individual zones (4) the lengths of all feeding fronts less than 6 m deep were measured using a GPS and their depth and location noted. All fronts included in the audit had sea urchins of commercial densities (as determined by commercial urchin divers participating in the audits).
Each fisher was asked to map sea urchin and kelp distribution in his zone. The acquired knowledge of where feeding fronts were located and where kelp beds were at risk of being overgrazed improved their ability to develop a harvest strategy.
Fishery monitoring was entirely from catch records and personal communication with fishers and buyers. Early in the fishery buyers provided mandatory catch records with weights and prices. Beginning in 1997 fishers were required to hire a commercial monitoring company to enter on a government database their daily catch records and fishing location as well as submit daily paper records. A company representative met the boat at landing for 20% of the trips to verify that the catch was reported correctly. However, these records were incomplete because some fishers chose not to report their fishing to the monitoring company.
Volunteer logs, including a detailed description of fishing location, diver hours, and gonad yield as a percentage of live weight (measured by the buyer at point of landing) were introduced in the 1994/95 season. These data were more complete than the mandatory sources and were most often used in this report.
The sequence of management decisions are listed in Table 2.
In August 1996 a harvester tied storm-tossed kelp (Laminaria sp.) into 70 bundles of about 35 kg each. These bundles were divided among three areas with dense sea urchins and no kelp and were weighted down with rocks. Sea urchin gonad yields (wet weight of gonads as percentage of sea urchin live weight) had been less than 5 % and had not reached commercial quality the previous fishing season. After 2-wk the bundles were completely covered with sea urchins. Two to three months later the three areas yielded 900 kg of commercial quality sea urchins with gonad yields of 10% to 13%.
In a nearby location a dense feeding front was located at 3-m depth and the remaining narrow kelp bed was at risk of being eliminated by sea urchin grazing. In July 1996 storm-tossed kelp was bundled as earlier mentioned and placed below the feeding front at 10-m depth in a line 55 m long. In November 400 kg of sea urchins with 10% gonad yield were harvested from the deeper line. The feeding front was also harvested and the next summer the bottom to about 10-m depth was largely free of sea urchins and was populated by newly recruited macroalgae. Four other areas 6-10 m wide and 25-40 m long with undersized (unmarketable) sea urchins and located on the seaward edge of shallow kelp beds were cleared of sea urchins and experienced significant expansion of macroalgae by 1-y later.
Moving overcrowded and underfed sea urchins to kelp was less successful. In several attempts 0% to 40% of the weight of transplanted urchins were recovered after 2-12 mo. In the more successful transfers the sea urchins were transported in collecting bags, the bags dropped overboard at the transplant sites, and divers emptied the urchins in a dense row at the edge of kelp beds. Urchins released into kelp beds or from the deck of a boat did not form feeding fronts and were not recovered.
None of nine "feed lots" was a commercial success. Legal sized sea urchins with small gonads were placed in wire cages and fed kelp. The labor costs were high and sea urchins in cages located in areas exposed to even moderate storm swells were killed. The cages deprived urchins of shelter and a substrate for firm attachment.
Fishery Independent Surveys
From mapping of their zones fishers' located feeding fronts and identified those with marketable sea urchins close to eliminating their kelp food supply. Several fishers harvested these fronts to reduce grazing pressure enough to allow kelp beds to expand to deeper water. Fishers were able to plan daily harvests to fish wave exposed locations on calm days and save sheltered locations for stormy days.
Because the license was the unit for management (rather than units of effort or catch) the number and spatial allocation of licenses were important considerations. Using the first and laterally the second method in Table 1 about 900 locations were observed during 19955000 to estimate the potential for new licenses. Based on these methods, and negotiation with fishers, 46 licenses were issued for the outer coast of Nova Scotia from Victoria to Shelburne counties (Fig. 1).
A more quantitative estimate of the area needed to support a license can be made using an average annual harvest in kg/m of feeding front. Nine harvested feeding fronts surveyed had a total length of 12,900 m. Logbook records of annual harvests from each of these fronts divided by the length of each averaged 5.4 kg/m (S = 2.5). Using annual harvests by active fishers ranging from 23,000-90,000 kg and with a potential of 5.4 kg/m, these licenses would need 4,300-16,700 m of front to maintain their catches. This method of zone allocation was not applied because the fishery stopped expanding before it was developed.
By 1999 the first 14 recipients of individual zones had completed the 4-y trial period. Industry and government representatives jointly developed audit criteria based on the length and depth of the sea urchin feeding fronts. Under-managed fronts were defined as locations where dense macroalgae extended to less than 6 m depth below low tide, in areas where the bottom substrate was capable of supporting macroalgae to that depth.
If the length of under-managed fronts exceeded 1,000 m a zone would be downsized to include no greater than 1,000 m.
Only one of the 14 zones audited met the criteria for well-managed (i.e., less than 1,000 m of front at less than 6-m depth (Table 3). All but two zones also had more than 1,000 m of front less than 4 m deep. For the 14 zones the total front less than 6 m and 4 m deep were 281 km and 192 km respectively.
An estimated 252 km of shallow front was not fished. Dividing the 1998-1999 landings by 5.4 kg/m approximated the meters of front fished by each fisher and totaled 89 km for the group (Table 3). The fraction of each fisher's catch taken from less than 6-m depth (not shown) times the length of front fished by each fisher summed to 29 km for the 14 fishers. Subtracting 29 km from the 281 km of front <6 m deep gave 252 km not fished. No doubt additional amounts located greater than 6 m deep and not surveyed were also unfished.
We expected the percentage gonad content to increase with time as a result of enhancement. Most plots of the mean annual gonad yields for 13 fishers for which we have 4 or 5 y of records showed only modest or no improvement (Fig. 4). From a starting value of about 10% three increased more than 3%, one increased about 2%, two decreased about 2%, and the remainder changed by 1% or less. The degree of underutilization of zones shown in Table 2 indicates area high-grading.
[FIGURE 4 OMITTED]
Likely, most fishers harvested only areas most accessible or with the best gonad yields.
Gonad yields for the fishermen who enhanced their stock were higher than for those who did not (Fig. 5). Daily percent gonad yields from one zone in eastern Nova Scotia where stocks were enhanced were compared with two nearby zones where they were not (unpaired t-tests). For the fishing months in common means were significantly higher for the enhanced zone (P < 0.01). Comparisons were also made between an enhanced and two nearby unenhanced zones in western Nova Scotia and also found to be different (P < 0.01).
[FIGURE 5 OMITTED]
Fishers were able to maintain gonad yield at a commercially acceptable level in spite of wider fluctuations in yields during the harvest season. In eastern Canada the green sea urchin typically spawns in April then gradually rebuilds gonads to a peak in March (Miller & Mann 1973, Himmelman 1978, Meidel & Scheibling 1998). Figure 6 gives the monthly mean values taken by the fishery in Halifax plus Guysborough Counties and Shelburne County in 1998/99. This is compared with the more variable monthly means from single feeding fronts at two locations in Lunenburg County located between these fishing areas (Meidel & Scheibling 1998).
If catch per unit effort (CPUE) is an index of stock abundance then catch per boat-day and catch per diver-hour should decrease when the stock decreases. Four fishers with zones lost a large portion of their stocks to disease between successive seasons and their season landings dropped by about one-half. However, their catch per day and per diver hour changed much less than their change in landings (Table 4). Although five of the eight differences in catch rates decreased between years, all differences were significantly less than proportional to the difference in seasonal landings (unpaired t-tests, unequal variances).
CPUE as an Index of Abundance
Even after losing a large fraction of their stock to disease, Nova Scotia sea urchin fishers nearly maintained their catch per diver-hour and boat-day. CPUE was found not to be a useful index of abundance in dive fisheries for the green sea urchin in Maine (Chen& Hunter 2003), red sea urchin in Washington (Bradbury 1991), South Australian abalone (Keesing & Baker 1998, Prince & Hilborn 1998, Shepherd et al. 2001), or sea cucumbers in California (Schroeter et al. 2001). It particularly overestimates abundance when stock biomass is low (Chen & Hunter 2003). However, correlations of annual landings and mean CPUE were shown for some sea urchin fisheries in North America and elsewhere (Andrew et al. 2002).
[FIGURE 6 OMITTED]
Enhancement of Sea Urchin Stocks
The benefits of extensive stocking of hatchery-reared juveniles in Japan has been sparsely evaluated (Agatsuma et al. 2004), but Tegner (1989) and Agatsuma et al. (2004) documented success. Tegner (1989) also reviewed Japanese results showing economic benefits from creating channels in rocky shoreline and stocking with poorly fed urchins. San Martin (2002) reported success in transferring large urchins from an area of poor to good food resources near Marseilles. Glantz (1992) increased the gonad yield of purple sea urchins in California by feeding chopped kelp on the sea bed.
Nova Scotia fishers enhanced stocks most successfully by adding bundled kelp to areas without macrophytes and by increasing harvest intensity in areas where kelp beds were threatened by sea urchin grazing. Moving sea urchins to kelp and cage culture in the sea were not successful.
Management and Assessment of the Nova Scotia Sea Urchin Fishery
Other North American sea urchin fisheries are regulated by minimum sizes, seasons, area closures, and TACs based on conservative percentages of fishable biomass (Andrew et al. 2002, Botsford et al. 2004).
In the Nova Scotia fishery individual fishers, and not government, were responsible for most assessment and management activities in keeping with the mechanism design approach. Government allocated fishing areas, advised fishers on resource husbandry, and after a few years audited their success or failure. Audit criteria were based on depth of the feeding front. (For sea urchin species, which do not form feeding fronts, the audit criteria might be modified to a minimum acceptable bottom cover by macrophytes.) Because diver-harvesters could see the urchin stock, gonad yields, and kelp abundance they were in a position to manage the resource on a trial and error basis and to judge the success or failure of their methods. Increasing the length of feeding fronts through enhancement can increase habitat carrying capacity and fishery yield. The trial and error approach did not require an understanding of the mechanisms regulating abundance although we did intend to involve fishers in studies of recruitment to feeding fronts (Duggan & Miller 2001).
Exclusive access has advantages over competitive access. In a competitive fishery a fisher should harvest any sea urchins of commercial value when they are first found or risk losing it to a competitor. Freedom to schedule harvests gave zone holders advantages of scheduling for weather, price, rate of recovery of feeding fronts, and state of gonad development. Individual fishers can benefit from their own enhancement activities, and by knowing their grounds they can reduce search time. There is no requirement for group agreement or participation.
Many resource management costs were eliminated or transferred to fishers. It was in the fishers' interest to police their own borders; only one charge was laid in 6-y for fishing illegally in a zone. Seasons were eliminated to free each fisher to exploit his zone to his best advantage. Without catch quotas or quota monitoring the incentive to misreport landings was reduced. The management agency could limit its catch monitoring to the analysis of fishers' logbooks and its fishery independent monitoring to zone allocation and zone audits.
However, disadvantages of this approach were clear. Persuading fishers to switch from competitive fishing to an unfamiliar method of resource allocation and surveying the stock to allocate zones entailed high start-up costs. Many zone holders fished their zones incompletely (Table 3) and, except for selective fishing effort, engaged in minimal stock enhancement. Here, enforcement of the management plan by the management agency was needed, but it was not provided. Because some of the zones were larger than fishers fished, it was in their individual best interest to fish only the portions that were most profitable or required the least effort. Initial allocation of oversized zones was necessary to overcome some fishers' resistance to restriction to one area. Had fishers lost the unfished portion of their zones as planned, the incentive to manage a zone completely would have been reinforced.
Given the loss of most of the sea urchin stock to disease in the early 1980s and again in the late 1990s (Miller 1985, Scheibling et al. 1999, Miller & Nolan 2000) the management plan should include provisions for collapsing the zones and allowing increased fishing when disease is detected.
Sustainability of the Resource
Dive fisheries can serially deplete small stocks (Prince et al. 1998, Prince & Hilborn 1998). This occurs in abalone fisheries when divers fish out each bed as they are discovered, perhaps to unsustainable levels. Egg fertilization rate in sea urchins increases with animal density (Pennington 1985, Levitan et al. 1992, Levitan & Sewell 1998, Wahle & Peckham 1999, Gaudette et al. 2006) and disturbing aggregations near the spawning season could reduce success (Brady & Scheibling 2006). Drag fisheries may have a greater impact on aggregations than dive fisheries because of its larger footprint on the habitat.
The Nova Scotia green sea urchin has several reproductive refuges from harvest: urchins too deep for divers to harvest, urchins of subcommercial densities, urchins with gonad yield below market acceptability, and urchin sizes between reproductive maturity at about 8 g and commercial size at about 60 g. Individual fishing zones would also reduce the risk of serial depletion by limiting total fishing effort and distribute the effort among zoned areas. Furthermore, a zone holder can afford to fish at a low exploitation rate and take only the best quality urchins without risk of another fisher taking the urchins left for another day. After near 100% mortality in the nearshore in early 1980s the stock recovered by the mid90s to support a fishery along most of the 400 km of affected coastline (Miller & Nolan 2000).
The Nova Scotia sea urchin fishery was well suited for management by fishers because of the simple macrophyte-sea urchin food chain, the stationary nature of both, and the spatial-temporal variability of sea urchin population parameters important to the fishery. Depths of feeding fronts and lengths of fronts calibrated for annual yields provided the bases for zone allocations and audits of management performance. Fishers' self-interest was compatible with small government input and adequate management of the resource, except where a zone included more acceptable quality urchins than a fisher chose to fish. In that case the fisher lacked the incentive to enhance the stock. This problem would likely be overcome if the resource required enhancement to meet their expected harvest or if they lost the portions of their zone not enhanced.
The authors acknowledge innovative work by license holders Alan Baker, Raymond Garland, and Andrew Snare in support of the management plan and in stock enhancement methods. N. L. Andrew, G. J. Sharp, and anonymous reviewers made constructive suggestions on the manuscript. The authors benefited from the participation of commercial sea urchin divers Ian Barkhouse and Wayne Chetwynd in our surveys.
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ROBERT J. MILLER * AND STEPHEN C. NOLAN
Bedford Institute of Oceanography, Dartmouth, Nova Scotia B2 Y 4A2, Canada
* Corresponding author. E-mail: email@example.com
TABLE 1. Fishery-independent survey methods and survey rate per day. Purpose Methods 1. Original method for View 100-500 m of near-shore (with or size of restricted without feeding front) at intervals of zones 1-5 km for presence of macroalgae and legal sized urchins 2. New method for Using GPS measure length of all feeding size of restricted fronts less than 13 m deep; note depth, zones location, and presence/absence of legal sized urchins 3. Lengths of feeding Diver measures front with metered fronts to calculate string laid out by swimming mean yield in kg/m of harvested front 4. Audit of utilization Measure length and depths of all feeding of restricted zones fronts <6 m deep, record exact locations using GPS Purpose Survey Rate/Day 1. Original method for ~20 intervals along 50 km size of restricted of shoreline and shoals zones 2. New method for ~10 km of front size of restricted zones 3. Lengths of feeding 2 km of front fronts to calculate mean yield in kg/m of harvested front 4. Audit of utilization 10-20 km of front of restricted zones <6 m deep TABLE 2. Sequence of regulations or events. Steps 5-11 apply only to fishers choosing zones. Steps 10 and 11 were not implemented. 1. Regulation of seasons, minimum urchin size, discarding of under-sized urchins, submit voluntary logbooks with fishing locations, catch, percent gonad yield, and diver hours 2. licenses restricted to counties 3. grounds surveyed for allocation of zones 4. a. fishers choose individual zones; b. fishers choose to fish competitively within counties 5. seasons eliminated 6. zones mapped by fishers 7. fishers enhance stocks 8. reference points developed based on depth of feeding front 9. zones audited using reference point 10. recalculate zone size based on audit results 11. in the event of disease, collapse zones until stock recovers TABLE 3. Results of the 1999 zone audit survey and mean depths fished in the 1998-99 season as reported in logs. All depths and lengths in meters. Feeding Front <6 m Deep Length of Front Fisher Length Mean Depth <4 m Deep A 300 5.20 0 B 5,900 4.60 1,700 C 6,000 4.30 1,400 D 16,400 3.20 8,300 E 22,000 3.60 11,800 F 13,400 3.50 6,100 G 19,000 3.70 6,800 H 3,300 4.90 0 I 13,000 4.20 3,100 J 29,700 2.90 22,600 K 32,700 3.60 18,500 L 66,400 2.10 66,300 M 1,900 0.80 1,900 N 50,700 1.10 43,900 Totals 280,700 192,400 Depth Fished Estimated Length in 98-99 Season of Front Fished Fisher Mean (S) in 98-99 A 12.1 (1.8) 6,400 B 9.4 (2.4) 9,800 C 9.7 (2.4) 8,000 D 10.3 (a) (2.2) 5,800 E 7.6 (a) (2.2) 2,900 F 7.0 (a) (1.5) 0 G 10.6 (a) (1.2) 3,200 H 5.5 (1.5) 1,100 I 7.9 (2.4) 11,900 J 5.8 (2.8) 16,800 K 6.4 (1.5) 13,400 L 6.7 (1.9) 1,900 M 9.1 (0.9) 3,300 N 5.2 (1.4) 4,900 Totals 89,400 (a) Depths for 1997-98, depth not provided for 1998-99. TABLE 4. Catch rates of four fishers in fishing seasons before and after reduction of the sea urchin stock by disease: season catch, mean and standard error (SE) of catch per boat-day, and per diver-hour. The top P for each fisher is the probability that the mean catch rates for the two seasons do not differ from 0 ([D.sub.mean] = 0) and the bottom P is the probability that the mean catch rates do not differ from rates proportional to the size of their season landings ([D.sub.mean] > 0). Catch Rates (kg) Per Boat-day Fisher Years Season Mean SE [D.sub.mean] P A 97/98 56,310 1,043 39 0 <0.01 98/99 32,601 795 26 604 <0.01 B 98/99 90,000 1,346 44 0 <0.01 99/00 46,000 1,133 44 1,099 <0.01 C 98/99 65,000 903 28 0 0.01 99/00 38,000 795 30 564 <0.01 D 98/99 58,000 916 51 0 0.02 99/00 21,000 1,251 118 2,252 <0.01 Catch Rates (kg) Per Diver-hour Fisher Years Mean SE [D.sub.mean] P A 97/98 84 2.5 0 0.92 98/99 83 2.5 63 -0.01 B 98/99 120 6.7 0 -0.01 99/00 75 2.9 73 -0.01 C 98/99 65 1.6 0 -0.01 99/00 58 1.7 51 -0.01 D 98/99 71 3.3 0 0.03 99/00 87 6.0 156 -0.01
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|Author:||Miller, Robert J.; Nolan, Stephen C.|
|Publication:||Journal of Shellfish Research|
|Date:||Aug 1, 2008|
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