Arturo Muhlia-Melo
Centro de Investigaciones Biológicas del Noroeste
S.C.
Km 2 Carr. San Juan de la Costa
El Comitan, Apartado Postal 128
La Paz, Baja California Sur, Mexico
ABSTRACT
Sportfishing, baitboat, purse seine, longline and drift gillnet fisheries in Mexico are briefly described in this paper. Regulations applied to these fisheries within Mexican Exclusive Economic Zone are also discussed. Longline and sportfishing interactions for several pelagic finfish species are discussed and potential interactions among the baitboat, purse-seine and sportfishing are pointed out. Future research in critical areas is proposed.
1. INTRODUCTION
The Mexican tuna and billfish fisheries in the Pacific consist of five gear types. They include troll (sportfishing), pole-and-line (baitboat), purse seine, longline and, more recently, drift gillnet.
1.1 Sportfishery
The sportfishery in the west coast of Mexico was initiated in the early 1950s (Ponce-Díaz, 1993). This fishery developed concurrently with development of the tourist industry along the west coast of Mexico. In the early 1980s a number of internationally recognized sportfishing ports were established along the west coast of Mexico. Historical records of Mexico's marine rod-and-reel sportfishery from 1969 to the present have been obtained by postcard surveys conducted by National Marine Fisheries Service (Squire and Muhlia-Melo, 1993). Catch has focussed on the principal billfish species including striped marlin, blue marlin, black marlin and sailfish. Some data on tunas and other big pelagics are also collected. Location of the most important sportfishing areas in the Pacific coast of Mexico include the southern tip of Baja California - Mazatlán, San Blas, Puerto Vallarta, Manzanillo, Ixtapa-Zihuatanejo and Acapulco. A review of the billfish fisheries and resource management by Mexico and the USA in the northeast Pacific Ocean has been presented by Squire and Muhlia-Melo (1993).
1.2 Baitboat and Purse Seine Fisheries
The baitboat fishery was initiated in Mexico in 1937 and reached a high in catches of 3,528 mt in 1965 (Muhlia-Melo 1987). The purse-seine fleet developed in the early 1960s and reached a high in production of 47,926 mt in 1987. Trends of carrying capacity of the purse-seine and baitboat fleets of Mexico from 1985 to 1993 are presented in Table 1.
Table 1. Carrying capacity (mt) of the Mexican tuna fleet in the eastern Pacific Ocean, 1985-93. (Data source: IATTC, 1986, 1987, 1988, 1989, 1991, 1992a, 1992b, 1993, 1994.)
|
Year |
Purse Seine |
Baitboat |
Total |
|
1985 |
45,935 |
1,458 |
47,393 |
|
1986 |
38,980 |
1,127 |
40,107 |
|
1987 |
47,926 |
1,269 |
49,195 |
|
1988 |
47,539 |
1,738 |
49,277 |
|
1989 |
46,087 |
1,840 |
47,927 |
|
1990 |
46,033 |
1,840 |
47,873 |
|
1991 |
42,129 |
992 |
43,121 |
|
1992 |
43,201 |
840 |
44,041 |
|
1993 |
42,632 |
685 |
43,317 |
The longline fishery in Mexican waters was initiated in the early 1950s by the expansion of the Japanese longline fishery into the eastern Pacific. High catch rates of tunas, billfishes and other species of big pelagics were made in an area from about the latitude of the Revillagigedo Islands (19° N.) to the southern portion of the Gulf of California, and northwest off Baja California Sur to north of Magdalena Bay (Squire and Muhlia-Melo, 1993). The amount of longline effort within 200 miles of Mexico totalled about 4 million hooks in 1973 (Joseph, 1981). The longline effort declined rapidly off Mexico after the establishment of the 200 nautical mile Exclusive Economic Zone (EEZ) by the government of Mexico in 1976; however, longline effort increased after 1980 with the granting of longline permits to established longline joint-venture operations. Trends of effort in the eastern Pacific from 1956 to 1980 and within Mexico's EEZ limits from 1971 to 1989 are presented in Figure 1. The dominant catch of this fishery in Mexican waters was billfishes and, in lesser proportion, tunas.
1.4 Drift Gillnet Fishery
As a result of the restrictions on the use of longline gear within Mexico's EEZ a new gillnet fishery developed in 1990 with 12 boats. In 1992, 27 permits were authorized by the government of Mexico and about 24 boats were in operation in 1993. Catches of around 1,000 mt of swordfish are estimated to be landed by this fishery annually. The amounts of tunas and other species taken by this drift gillnet fishery are unknown (Squire and Muhlia-Melo, 1993).
2. REGULATIONS
In 1983 the Mexican government established a sportfishery preserve which extended from the coastline to 50 nm offshore along the Pacific coast of Mexico (Anonymous. 1983). Commercial fishing was restricted within this zone, and only Mexican flag vessels could fish the waters outside of the restricted zone out to 200 nm. In 1987 Mexico issued new regulations regarding the inshore limits of longline operations by permit holders (Figure 2 and Anonymous, 1987a). This new limit resulted in an extension of the former prohibited fishing area to a considerable distance offshore. The new regulations established additional protected areas off the southwest coast of Baja California, the entrance of the Gulf of California, and the Tehuantepec Bight (Squire and Muhlia-Melo 1993).
3. INTERACTIONS
3.1 Overlapping Areas of Longline and Purse Seine Fisheries
Geographical distribution of catch of tunas by the longline fishery showed high catches in areas around the west coast of Baja California peninsula and the southern portion of the Gulf of California; low catches were encountered in central areas of Mexico (see Miyabe and Bayliff, 1987 for the period 1971-1980; Nakano and Bayliff, 1992 for 1981-1987; and Maciás-Zamora et al., 1994 for 1980-1990). These areas are also covered by the purse-seine fishery in the eastern Pacific (IATTC, 1987, 1988). A schematic representation of the overlapping areas is shown in Figure 3.
A potential for interaction between longline and purse-seine tuna fisheries exists in Mexican waters. This subject for the eastern Pacific has been discussed by several authors, the more recent works have been presented by Punsly and Nakano (1992) and Nakano and Bayliff (1992). Tuna catches of the longline fishery from 1980 to 1990 ranged between 0 to 18% of the total catch (Anonymous 1987b); geographical distribution corresponds to the areas shown in Figure 3.
Longline fishing in Mexico's EEZ has not been authorized since 1990; however, there is a possibility that longlining may be reactivated in the future.
3.2 Longline and Sportfishing Interactions
The 1987 regulation affected the operation of the longline fishery, but did not affect the operation of purse-seine and baitboat fishing because the regulation does not apply to tunas.
Prior to the establishment of Mexico's EEZ regulation in 1976, fishing effort by the Japanese longline fleet in the eastern Pacific (east of 130° W.) increased to about 85 million hooks (Figure 1). From 1976 to 1988 the joint-venture longline fleet applied an effort within Mexico's EEZ of about 1.9 million hooks (Figure 1). These two periods were compared in relation to the CPUE of sailfish of the sportfishing tournaments in Manzanillo (Maciás- Zamora et al., 1994). A negative trend was noted from 1956 to 1976 followed by a period of relatively stable CPUE (Figure 4). Similar patterns are observed for the striped marlin caught in the sportfishing tournaments held in Baja California Sur (Figure 5). However, these tendencies are not observed for striped marlin taken in areas of Mazatlán and Acapulco. In this case there is no evidence of the increase trends during the second period (Figure 6).
The interaction between the commercial longline fishery and the recreational fishery, as determined from the Angler Survey (organized by the Southwest Fisheries Science Center of NMFS in La Jolla) can be seen by examining the striped marlin catches (Squire, 1991). Longline catch rates for striped marlin off Baja California declined from about 18 fish/1,000 hooks fished to about 9 fish/1,000 fished during the period 1963-1976. Angler catch rates, determined by The Annual Billfish Angler Survey showed a decline from about 0.6 fish/day to 0.3 fish/day during the same period. Catch rates increased from 0.36 to about 0.57 fish/angler day during 1977-1980 when longline was prohibited off Mexico (Squire, 1991). During the 1982-1984 period another decline became evident; the decline seemed to coincide with the restarting of the joint-venture longline fishery. From 1985 to 1992 the catch rates of the sportfishery increased up to about 0.6 fish/angler day (Holts, 1994). The CPUE of striped marlin taken in the sportfishing tournaments in Baja California showed a similar pattern of that of sailfish in central Mexico (Squire and Muhlia-Melo, 1993).
From these results we can conclude that increasing tuna/billfish longline effort in areas by recreational fisheries could have a substantial negative impact on the recreational catch, especially the billfishes. Similar situations have been observed in other parts of the world such as the Gulf of Mexico for white marlin in the Atlantic Ocean (Squire, 1991).
It is important to point out that records of the tunas captured by recreational anglers are not obtained on a consistent basis; tuna data are only collected for specific projects. There is a need to establish a data bank, where data collected from all fisheries can be maintained.
According to the distribution of the fisheries in Mexico's EEZ (Figure 3), the sportfishing areas are closest to the longline fishery along the west coast of Baja California peninsula and central-south Mexico. At present it is not possible to find any evidence of tuna interactions between the longline and the recreational fishery in Mexican waters. Tuna/billfish longline fishing permits to operate in Mexico's EEZ have not been issued since 1990.
3.3 Baitboat and Sportfishing
During the period of 1989-1993 the baitboat tuna fleet operating in Mexican waters showed a declining trend in carrying capacity; the decline was from 1,840 mt in 1989 to 685 mt in 1993 (Table 1). There is no evidence of interaction between the baitboat and sportfishing in Mexico despite the overlapping areas of operation of the two fisheries along the west coast of Baja California peninsula and at the southern portion of the Gulf of California. It is generally accepted that the baitboat fishery is capable of targeting tunas, thus, the bycatch of this fishery is very restricted. It should be noted that purse-seining with small tuna boats may be overlapping in operational area with rod-and-reel and baitboat fishing in the same coastal waters of the region.
4. FUTURE RESEARCH
4.1 Interactions
In order to understand the existence of any interaction between these fisheries, it is necessary to establish a standardized data bank system. Sportfisheries within Mexico are very complex and extend along a considerable part of Mexico's coastline. There are about 16,000 sportfishing boats and the number of sportfishing ports is increasing steadily. Interactions may occur in different fishing areas and between different gear types. What can be concluded from this preliminary work is that there are two major areas of research to analyse fisheries interactions. One area of research is the area of high concentration of tunas and billfishes located south of the Gulf of California and northward along the west coast of the Baja California peninsula. In this area the purse-seine, baitboat, gillnet and sportfishing fisheries overlap. This area is restricted to the longline fishing. The second major area is from the north-central Mexico, Mazatlán down to the Gulf of Tehuantepec. This is an important sportfishery area for sailfish.
4.2 Ecological Studies
There are a number of seamounts around the southern portion of the Gulf of California. It has been observed that in these locations big pelagic fishes like tunas, billfishes and sharks are known to aggregate. Studies related to the behaviour of the sharks in these locations have been carried out by Klimbley (1982, 1987); Klimbley and Nelson (1984); Klimbley and Butler (1988); and Klimbley et al., (1988). A research group from the CIBNOR initiated preliminary experiments on the ecological structure of the pelagic communities in 1992. This project involves studies of environmental factors affecting the structure of these communities, specific studies of reproduction, behaviour and food chain. Since seamounts are also important for sportfishing and commercial fishing, the results of these studies may help to understand the availability of the resources and the efficiency of fishing gears applied to fishes.
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