Gulf of Mexico Origin, Waters, and Biota: Volume 4, Ecosystem-Based Management

19 Ecosystem- Based Management of Coasta lFisheries in the Gulf of Mexico

337 ≋ Coastal Fishery Catches and Ecological Framework Generally, a clear pattern of factors responsible for variation in fisheries catches from estuarine and coastal shelf systems worldwide does not exist (e.g., Nixon 1982; Kapetsky and Lasserre 1984; Caddy and Sharp 1986; Bayley 1988; Alvarez-Borrego 1994; Pauly and YáñezArancibia 1994; Mann 2000; Chesney and Baltz 2001). But, there are consistent influences of ecological parameters on the production of fish and shellfish in coastal ecosystems , such as 1. River runoff onto the continental shelf (Chapman 1966; Sutcliffe 1973; Yáñez-Arancibia, Soberón Chávez et al. 1985; Caddy and Sharp 1986; Pauly 1986a; FAO 1995; Yáñez-Arancibia et al. 2004). 2. Terrigenous sediments discharge (and organic detritus) onto coastal soft-bottom shelf communities (Caddy and Sharp 1986; Deegan et al. 1986; Pauly 1986a; Cyrus and Blaber 1992; FAO 1995; Yáñez-Arancibia 2006; Sanchez-Gil et al. 2008). 3. Primary production (Nixon 1982; Nixon et al. 1986; Nixon and Buckley 2002; Yáñez-Arancibia et al. 1993; Pauly and Christensen 1995a, 1995b; Weinstein and Kreeger 2000; Deegan 2002; YáñezArancibia et al. 2004, 2007). 4. Coastal wetland vegetated areas (Turner 1977; Zimmerman et al. 1984; Yáñez-Arancibia, Soberón Chávez et al. 1985; Deegan et al. 1986; Pauly and Fisheries are an excuse for doing the right thing. In the public mind, fishes are good for something and adequate justification for resource management policies and actions that also serve other aspects of the public trust. To quote Aldo Leopold (1949), “A thing is right when it tends to preserve the integrity, stability, and beauty of the biotic community. It is wrong when it tends otherwise.” Thus, identifying fish needs and managing for sustainable fisheries advances many cultural, economic, and environmental matters (Pauly and Christensen 1995a). Longterm stewardship of fisheries is more cost effective than short-term profitability (Seijo and Caddy 2000). With a position near the top of the trophic pyramid, the health of fish populations reflects the health of lower trophic levels and influences the health of higher levels (Pauly et al. 1998; Caddy and Garibaldi 2001). To be healthy, sustainable fishery populations need more than clean water, they need to be parts of productive and healthy ecosystems (Karr 1981; Pauly and Christensen 1995b). Proper management to maintain the health of fish populations also has indirect effects on the resilience of ecosystems upon which they and human populations depend (Adger et al. 2005). Therefore, developing knowledge that leads to the wise and sustainable management of fishes through studies that advance our understanding of bioenergetics, habitat requirements, predator–prey interactions, community structure, responses to perturbations, population dynamics , recruitment potential, and fisheries will have farreaching benefits for the region, now and in the future. 19 Ecosystem-Based Management of Coastal Fisheries in the Gulf of Mexico Environmental and Anthropogenic Impacts and Essential Habitat Protection Donald M. Baltz and Alejandro Yáñez-Arancibia 338 ~ Baltz and Yáñez-Arancibia However, estuaries and coastal lagoons do not have uniformly high yields and indeed, the frequency distribution of Kapetsky’s yield data is strongly skewed (Pauly and Yáñez-Arancibia 1994). Some factors leading to this nearly log-normal distribution result from the inclusion of numerous unproductive lagoons: (1) extreme salinity and temperature fluctuations, turbidity, anoxic conditions or toxic discharges (Gunter 1967; Cyrus and Blaber 1992; Araujo et al. 2000; Yáñez-Arancibia et al. 2004; Cowan et al. 2011), (2) very shallow sills that prevent sufficient recruitment (Quasim 1973a,1973b; Pauly and YáñezArancibia 1994; Nagelkerken et al. 2000), and (3) lack of sufficient fishing effort to reveal potential harvestable biomass (Quignard 1984; Bayley 1988). The few extremely productive lagoons highlighted by Kapetsky (1984) may benefit from a number of factors (Pauly and Yáñez-Arancibia 1994): (1) a coastal habitat that supports a large recruitment, (2) fertilization via agricultural runoff or human sewage and through water exchanges with the sea, and (3) a management regime that optimizes the incoming recruitment. Following a synthesis extracted from Day et al. (1989), Alvarez-Borrego (1994), and Mann (2000), in general, estuarine fish productivity is within the range of 10– 100 g m−2 yr−1 wet weight (equivalent to 10–100 t/km2 ). If the carbon content is roughly 10% of the wet weight, this translates into 1–10 g C m−2 yr−1 , derived from primary production in the range of 200–400 g C m−2 yr−1 (Mann 2000). World catches of some important estuarinerelated species have...