Tuesday, February 22, 2011

Elasmobranch fishing in Baja!

Tacos with Manta Ray - apparently still popular.

Upon reading this paper, I was reminded of my first trips to Baja.
That was in the early 80ies aboard Tim Means' venerable Don Jose, and the Baja Explorador. Everybody was there to see the Hammerheads, huge schools of pelagics, Marlin and tame Mantas. We were young, reckless and stupid, the tequila never stopped flowing and life in general was good.
Except for the fact that every restaurant in La Paz had Manta on the menu.

Looks like nothing has changed.
From the paper

The artisanal elasmobranch fishery of the Pacific coast of Baja California, Mexico

Daniel Cartamila, Omar Santana-Morales, Miguel Escobedo-Olvera, Dovi Kacev, Leonardo Castillo-Geniz, Jeffrey B. Graham, Robert D. Rubin and Oscar Sosa-Nishizaki

Artisanal fisheries account for up to 80% of elasmobranch fishing activity in Mexican waters, yet details associated with fishing effort and species composition are generally unavailable.

This paper describes a survey of the artisanal elasmobranch fishery of the Pacific coast of Baja California, Mexico from 2006 to 2008.
The objectives were to determine the geographic extent, size, and targets of the artisanal fishery, and to describe the catch characteristics at Laguna Manuela, an artisanal camp where elasmobranchs are the primary target. For the latter, we used a combination of beach surveys and a novel survey method involving the identification of discarded carcasses. Forty-four artisanal fishing camps were identified, of which 29 (66%) targeted elasmobranchs at least seasonally, using primarily bottom-set gillnets and longlines.

At Laguna Manuela 25 species of elasmobranchs were documented.
Gillnetting accounted for 60% of fishing effort, and the most commonly captured species were Rhinobatos productus, Zapteryx exasperata, and Myliobatis californica. Longline fishing accounted for 31% of fishing effort, and the most commonly captured species were Prionace glauca and Isurus oxyrhinchus.

Catch was composed of mainly juveniles for many species, indicating that the immediately surrounding area (Bahia Sebastian Vizcaino) may be an important elasmobranch nursery habitat. The results of this study will serve as a baseline for determining future changes in the artisanal fishery, as well as changes in species demography and abundance.


4.3. Management implications

Although no base-line data comparable to the present study exist in western BC, interviews with older fishermen suggest that both the abundance and average size of elasmobranchs have declined significantly in recent decades off the western coast of BC.
Many of these declines have been exacerbated by a historic lack of governmental regulation. However, several steps have recently been taken to manage elasmobranch fisheries in Mexican waters. For example, the Mexican National Institute of Fisheries recommended a moratorium on the issuance of new elasmobranch fishing permits in 1993 (Castillo-Geniz et al., 1998), which was implemented in 1998 (Sosa-Nishizaki et al., 2008). This was followed in 2007 by NOM-029-PESCA-2006 (DOF, 2007), a major piece of legislation that includes regulations specific to artisanal fisheries.

Some general predictions as to how NOM-029 will affect artisanal Pacific BC fishers can be made based upon the present study.
Artisanal longline fishers in BC typically deploy up to 500 hooks, while elasmobranch gillnet fishers use multiple gillnets per vessel with mesh sizes of 6–12 cm. NOM-029 guidelines limit artisanal longline fishers to a maximum of 350 hooks, and limit gillnet fishers to the use of one gillnet per vessel with a minimum mesh size of 15 cm. Most longline fishers will not have to dramatically modify fishing practices to conform to NOM-029. Indeed, NOM-029 may be beneficial to artisanal longliners in that it restricts larger commercial longline vessels to waters 20 nautical miles (nm) or more from shore, thus reducing competition with artisanal vessels, which are restricted to only 10nm from shore.

However, gillnet fishers will not only have to greatly reduce the number of gillnets deployed, but the larger mesh size required will result in reduced catch rates of smaller fish.
Although NOM-029 may have a negative economic impact on artisanal gillnetters, it represents an important step towards the conservation of elasmobranchs in Mexico. However, very few fishers interviewed in the survey fully understood the NOM-029 guidelines, and less were in compliance with them (e.g., the mandatory completion of logbooks).

The declines in elasmobranch abundance noted in many parts of Mexico (Bonfil, 1997; Castillo-Geniz et al., 1998; Perez-Jimenez et al., 2005) perhaps justify a decrease in elasmobranch-directed fishing effort by artisanal fisheries.
Given the higher ex-vessel prices for most teleost and invertebrate species harvested by BC artisanal fishers, a shift in effort to these more sustainable resources may be warranted. Vieira and Tull (2008) determined that the cessation of elasmobranch fishing by artisanal fishers in Indonesia did not result in substantial economic hardship, as fishing could be directed towards alternative species. For example, the Humboldt squid is a major longline bycatch that was viewed as a plague by fishers because it would become hooked before sharks but had no ex-vessel value. This species potentially represents a major alternative target for artisanal fishers (Ehrhardt et al., 1983), and an export market is currently in development (Jara, personal communication).

Further studies are necessary to assist management of artisanal elasmobranch fisheries along the Pacific coast of BC.
A continuous monitoring program that provides location-specific catch data is needed to provide realistic estimates of total elasmobranch landings. Biological studies detailing aspects of age and growth, diet, reproduction, and spatial dynamics are required to conduct stock assessments and evaluate sustainability of the most heavily exploited shark and ray species (Gallucci et al., 1996).

Socioeconomic surveys would be useful to identify social and cultural drivers of fishing pressure, and monitor changes in the economic conditions of fishers over time (Bunce et al., 2000; Cinner and McClanahan, 2006; Battaglia et al., 2010).
In addition, alternative avenues of management should be explored, such as the expansion of a limited-access fishing cooperative system, which has been shown to encourage sustainable stewardship of coastal resources (Young, 2001; Basurto, 2005).

The status of elasmobranchs in Mexico is also of concern to U.S. fisheries management, as elasmobranchs are a shared resource of ecological and economic importance to both countries.
Many commercially valuable pelagic shark species, such as the blue, the common thresher, and the mako, have geographical ranges that expose them to fisheries in both the U.S. and Mexico (Hanan et al., 1993; Obrien and Sunada, 1994; Gonzalez, 2008; Escobedo-Olvera, personal communication). Though less understood, the movement patterns of many coastal sharks and batoids likely span the international border as well (Ebert, 2003).

Ultimately, binational management strategies will be required that take into account mortality introduced through the activities of fisheries in both countries to calculate acceptable harvest levels.

As always, it is multifaceted and complicated.
And this without counting the additional threats posed by poachers to Sharks, Turtles and Sea Lions alike - remember this witness account?

I've recently been spending some quality time with fellow marine conservationists and we were commenting about the sheer size of the problem and about how difficult it is to find equitable solutions that whilst protecting vulnerable stocks, also take into account the legitimate concerns and aspirations of all stakeholders.
So true!

The solution?
Sustainability - what else?

Not easy - but slowly slowly, we're getting there!

PS of interest, the bigger Sharks being caught comprise Shortfin Mako, Blue, Smooth HH and Common Thresher and alas, very small GW - but neither Scalloped HH nor Bull.
Go wonder.

1 comment:

BeachNomad said...

Actually saw this presentation at ASIH last year. The pictures he had associated with it were just insane.. Huge fields of carcasses, it was heartbreaking for any elasmo fan