NOAA Seasonal Changes in Abundance and Compelling
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302 NOAA First U.S. Commissioner National Marine Fishery Bulletin established 1881 of Fisheries and founder Fisheries Service of Fishery Bulletin Abstract—We used scuba over fixed- width strip transects to monitor sea- Seasonal changes in abundance and compelling sonal abundances of brown rockfish evidence of migration for 2 rockfish species (Sebastes auriculatus) and copper rockfish (S. caurinus) on a nearshore (Sebastes auriculatus and S. caurinus) inhabiting artificial reef in Puget Sound, Wash- ington, over a 7-year period. Spring a nearshore, temperate-water artificial reef and fall abundances were intermedi- ate and marked transitional phases Larry L. LeClair (contact author) between seasons of highest (sum- Ocean Eveningsong mer) and lowest (winter) abundance for both species. Analyses of length Jesse M. Schultz classes indicated that the numbers of seasonal juvenile recruits were Email for contact author: [email protected] not sufficient to account for the marked differences in abundance Washington Department of Fish and Wildlife between summer and winter. For 600 Capitol Way North both species, the proportion of large Olympia, Washington 98501 fish (≥20 cm in total length) to the total number observed in summer and winter was significantly greater during the winter. Late-stage gravid brown rockfish occurred in greatest abundance during the spring and late-stage gravid copper rockfish Understanding fish movement is par- epis) also undergo seasonal migra- were observed only in the summer. amount to the design and implemen- tions (St-Pierre2), and establishment We examined auxiliary data from tation of effective resource conser- of the commercial fishery season by a genetics study of brown rockfish vation and management strategies. the International Pacific Halibut that was conducted concurrently at the reef and interpreted the results, Movement influences the dynamics, Commission is designed in large part along with our survey findings, as demographics, and genetics of popu- to protect offshore spawning popula- providing compelling evidence of lations; the structure and function tions (Loher, 2011). seasonal migrations on and off the of ecosystems; species interactions; Fish movement also has crucial reef. modes of energy transfer; and bio- implications for the design of scien- diversity (Rothschild, 1986; Frank, tific sampling strategies and stock 1992; Merz and Moyle, 2006; Clark et assessments, and movement poses al., 2009; Condal et al., 2012). Known both operational and conceptual chal- patterns of movement are often key lenges for the selection of appropriate considerations in the development temporal and spatial scales in ecolog- of harvest management plans es- ical studies. Inferences about the eco- tablished to protect fish populations logical processes under investigation from overexploitation. For example, may be constrained or confounded in the northeast Pacific Ocean, ling- when, as is often the case, scales of cod (Ophiodon elongatus) are widely operational convenience, rather than believed to participate in seasonal ecological relevance, are incorporated nearshore–offshore spawning mi- into study designs. Failure to identi- grations (Jagielo, 1990, 1995), and fy and integrate fish movement into in some regions (e.g., Puget Sound), study designs can lead to the selec- Manuscript submitted 20 October 2015. recreational fisheries that target tion of temporal or spatial scales of Manuscript accepted 19 April 2016. lingcod are managed to protect near- observation that are ill-fitted to the Fish. Bull. 114:302–316 (2016). shore spawning fish (Palsson et al.1). study objectives, particularly when Online publication date: 6 May 2016. Pacific halibut (Hippoglossus stenol- movement occurs over multiple habi- doi: 10.7755/FB.114.3.4 tat types. Sampling strategies that The views and opinions expressed or 1 Palsson, W. A., T. J. Northup, and M. W. implied in this article are those of the Barker. 1998. Puget Sound Ground- 2 St-Pierre, G. 1984. Spawning loca- author (or authors) and do not necessarily fish Management Plan, 48 p. Washington tions and season for Pacific halibut. Int. reflect t he p osition o f t he N ational Dep. Fish Wildl., Olympia. [Available Pac. Halibut Comm., Sci. Rep. 70, 46 Marine Fisheries Service, NOAA. at website.] p. [Available at website.] LeClair et al.: Seasonal changes in abundance and migration of Sebastes auriculatus and S. caurinus 303 focus on single habitat types are also subject to bias 2003), and presumably improving, these models rarely when based on untested assumptions about habitat incorporate fish movement (but see Attwood and Ben- use, extent of home range, and site fidelity, as reviewed nett, 1995; Roberts and Sargant, 2002; Berezansky et by Pittman and McAlpine (2003). These authors assert al., 2011). Understanding the frequency, periodicity, and that if information on movement is not available, the scale of fish movement will aid modelers and resource assumption of single habitat use should be considered managers in choosing and scaling MPA sites, and in carefully or rejected entirely. They advocate for an as- constructing MPA networks that adequately serve the sumption of the use of multiple habitats because it al- ecological needs of species targeted for conservation. lows for the consideration of broader-scale movement In this study, we seasonally monitored the abun- and potential linkages among habitat types. Movement dance of 2 demersal rockfish species, brown rockfish patterns, whether over short (e.g., diel) or long (e.g., (Sebastes auriculatus) and copper rockfish (S. cauri- seasonal, annual) temporal scales, rank as one of the nus) over a 7-year period on an artificial reef in Puget most important behavioral sources of bias in fish stock Sound, Washington. Counts for each of the 2 species assessments (Gayanilo and Pauly, 1997; Sparre and were obtained by using scuba-based underwater visual Venema, 1998). Statistical methods for incorporating censuses (UVCs) conducted over fixed-width strip tran- patterns of fish movement into stock assessments are sects. Brown and copper rockfish belong to the subge- advancing (Hilborn and Walters, 1992; Methot, 2011), nus Pteropodus and occur sympatrically in many re- and the integration of known fish behavior parameters, gions of the northeast Pacific Ocean, including much of such as diel and seasonal movements, will likely lead Puget Sound. They share similar life history attributes, to substantial improvements in the accuracy of stock habitat affinities, behavioral characteristics, and food assessment models (Fréon et al., 1993). preferences (Washington et al.3; Lea et al., 1999; Stout Although the potential conservation benefits of indi- et al., 2001; Love et al., 2002) and, in Puget Sound vidual marine protected areas (MPAs) have been dis- there is evidence of hybridization between the species cussed for decades, there is currently a growing world- (Seeb, 1998; Schwenke, 2012). In Washington State, wide interest in establishing coordinated networks of they are managed as “bottomfish” and brown rockfish MPAs that are ecologically joined over broad geographic stock status throughout Puget Sound is classified as regions, and this approach has been advocated for rock- “precautionary,” whereas copper rockfish are classified fishes in the northeast Pacific Ocean (Yoklavich, 1998; as either precautionary (north Puget Sound) or “vul- Parker et al., 2000). Further, understanding migrations nerable” (south Puget Sound), as defined by Palsson et and other movement patterns of adult rockfishes has al.4 been identified as critical for formulating effective re- Although tagging studies involving brown or copper covery plans that may include MPAs for rockfishes in rockfish have occurred throughout much of the range Puget Sound (Wyllie-Echeverria and Sato, 2005). The of these species and have encompassed a variety of in- trend toward MPAs, however, is not without controver- vestigative objectives (Miller et al., 1967; Miller and sy—much of it centering on how to choose and config- Geibel, 1973; Dewees and Gotshall, 1974; Hallacher, ure MPA sites into mosaics that are adequately sized 1977; Walton5; Laufle6; Gowan, 1983; Mathews and and placed to achieve prescribed conservation goals. Barker, 1983; Hueckel et al.7; Matthews, 1985; Mat- The related and equally critical issue of how best to thews et al., 1987; Hartmann, 1987; Matthews, 1990a; assess the performance of such networks once estab- Matthews, 1990b; Lea et al., 1999; Eisenhardt, 2004; lished is also a topic of considerable debate. The size Lowe et al., 2009; Tolimieri et al., 2009; Reynolds et and placement controversy owes much of its genesis to al., 2010; Longabach, 2010; Starr et al.8; Hannah and attempts at applying theories of island biogeography to the design of nature reserves (Diamond, 1975) and 3 continues under what is widely known as the SLOSS Washington, P. M., R. Gowan, and D. H. Ito. 1978. A bio- logical report on eight species of rockfish (Sebastes spp.) from (single large or several small) debate (Simberloff and Puget Sound, Washington, 50 p. Northwest Alaska Fish. Abele, 1982). Fundamental to the debate is the con- Cent. Proc. Rep. Northwest Alaska Fish. Cent., Natl. Mar. cept of source-sink dynamics (Pulliam, 1988) whereby, Fish. Serv., NOAA, Seattle. [Available at website.] 4 under optimal MPA performance conditions, increased Palsson, W. A., T.-S. Tsou, G. G. Bargmann, R. M. Buck- ley, J. E. West, M. L. Mills, Y. W. Cheng, and R. E. Pa- regulatory