Approaches to the assessment and management of multispecies skate and ray fisheries using the Falkland Islands fishery as an example

Abstract

Eleven rajid species are taken around the Falkland Islands, with four species, Bathyraja griseocauda, Bathyraja albomaculata, Bathyraja brachyurops, and Raja flavirostris dominating commercial catches and generally occurring together. Catch limits for individual species are not used in management because species are not separated in the catch or reported separately. The catch per unit effort for the mixed rajid assemblage was standardised using generalised linear modelling techniques, and two production models were used to estimate stock size and sustainable yield. Maximum likelihood methods were used to demonstrate that there are two distinct rajid communities, one to the north and one to the south of the Falkland Islands, which have different sustainable yields. Changes in species composition over the 10-year course of the fishery confirm theoretical expectations that the larger, later-maturing B. griseocauda is being replaced in catches by the smaller, earlier-maturing B. albomaculata and B. brachyurops. These changes in composition were evident after only 6 years of directed fishing. The current fishery to the north of the Falkland Islands appears to be stable at an annual catch of about 3000 t, which is between 6.5 and 7.6% of the estimated pre-exploitation biomass.

Age, Growth and Maturity of the Commercial Ray Species from the Irish Sea

“…The affects of long-term exploitation on life history traits through changes in stock structures and relative abundances have also been suggested for a number of other ray fisheries (Anon, 1999b;Agnew et al, 2000;Kulka and Miri, MS 2003). For the Irish Sea it is apparent that historical levels of fishing mortality were too high to sustain the slow growing (K = 0.060) and late maturing (11 yrs) common skate (R. batis), which was commercially extirpated in the 1970s (Brander, 1981).…”

From coexistence to competitive exclusion: can overfishing change the outcome of competition in skates (Chondrichthyes, Rajidae)?

“…The white-dotted skate, Bathyraja albomaculata, and the Patagonian skate, B. macloviana, are two common skates affected by these fisheries. Both species are targeted by the Islas Malvinas rajid fishery (Agnew et al, 2000) and as bycatch in finfish trawlers targeting Argentine hake, Merluccius hubbsi, southern blue whiting, Micromesistius australis, hoki, Macruronus magellanicus (Brickle et al, 2003), and red shrimp, Pleoticus muelleri (Cedrola et al, 2005).…”

Skate-ing on thin ice: molecular ecology of longnose skates in the Southeast Pacific Ocean

“…Management and conservation of skates arise as a necessary duty for fishing countries in order to maintain biodiversity and ecosystem structures (Agnew et al, 2000;Dulvy et al, 2008). This research thesis provides the basic information required to clarify taxonomic and systematic issues within the Family Rajidae.…”

“…The biology and ecology of longnose skates is poorly known and requires further morphological, taxonomic and molecular research in spite of being one of the largest taxa within batoids (Compagno, 1999a;Ebert & Compagno, 2007) and have been subject to intense fishery exploitation (Baum et al, 2003;Myers & Worm, 2005;Myers et al, 2007;Dulvy et al, 2008Dulvy et al, , 2014Ferretti et al, 2008). Intense local fisheries with unmanaged landings are often accompanied by a lack of biological information required to maintain a healthy fishing stock (Ferretti et al, 2008(Ferretti et al, , 2010, and it has been suggested that longnose skates are generally vulnerable to stock collapse even when subjected to low levels of fishing pressure (Agnew et al, 2000). (Casey & Myer, 1998;Francis et al, 2001;Dulvy et al, 2008;Dulvy & Forrest, 2010).…”

“…Although there are basic identification keys and field guides for longnose skates of the southeast Pacific, poor species identification and the lack of specific landing records are big issues for fishery management and quota allocation, impairing conservation management. In particular, these two commercially important species, Z. chilensis and D. trachyderma, have an additional vulnerability as both are endemic to southern South America, occurring in temperate-cold waters (De Buen, 1959;Leible & Stehmann, 1987;Agnew et al, 2000;Menni & Stehmann, 2000;Gomes & Picado, 2001;Bustamante et al, 2014b).…”