CALIFORNIA STATE UNIVERSITY, NORTHRIDGE RECRUITMENT, GROWTH RATES, PLANKTONIC LARVAL DURATION, AND BEHAVIOR OF THE YOUNG-OF-THE-YEAR OF GIANT SEA BASS, STEREOLEPIS GIGAS, OFF SOUTHERN CALIFORNIA A thesis submitted in partial fulfillment of the requirements for the degree of Masters of Science in Biology By: Stephanie A. Benseman December 2017 The thesis of Stephanie A. Benseman is approved by: __________________________________________ ___________________ Michael P. Franklin, Ph.D. Date __________________________________________ ___________________ Mark A. Steele, Ph.D. Date __________________________________________ ___________________ Advisor: Larry G. Allen, Ph.D., Chair Date California State University, Northridge ii ACKNOWLEDGEMENTS I would like to express my gratitude to the following people for making this research possible. To all my family, friends, and loved ones. To all my diver buddies who braved the cold to help me search for hours for a needle in a haystack. To my Biology girls (Leah, Dani, Beth, and Stacey) for always being there to support me. To Larry Allen for your inspirations, Mike Couffer for your dedication, Mike Franklin for the laughs, Richard Yan for your countless hours of otolith work, Chris Mirabal for your confidence in me, Milton Love for your support, CSUN for your generosity, and just because babies. Thank you all. iii DEDICATION This work is dedicated to my family, who drive me crazy but I love and could not image being the person I am today without them. iv TABLE OF CONTENTS Signature Page ii Acknowledgements iii Dedication iv Abstract v Introduction 1 Methods 7 Results 13 Discussion 17 References 27 Appendix: Figures 34 v Abstract Recruitment, Growth Rates, Planktonic Larval Duration, and Behavior of the Young-of-the-Year of Giant Sea Bass, Stereolepis gigas, off Southern California. By: Stephanie A. Benseman Master of Science in Biology Little is known about the life history of Stereolepis gigas due to the over exploitation of their fishery in the early 1900’s, and depressed populations have prevented much research. A completed life history information on an ecologically, and once economically, important species such as the Giant Sea Bass (GSB) is critical for both the continued successful management of that fishery and a baseline for successful scientific studies. Therefore, the goals of this study include 1) determining distribution and general ecology for the YOY of S. gigas populations in the wild, 2) estimating growth rates, based on site aggregations in the wild, and otoliths analysis in the lab, and finally 3) confirming pelagic larval duration and the general temporal scale of their spawning period. One hundred and fifty SCUBA surveys were conducted to census waters with sandy benthos across southern California from 2013-2016. I documented early life ecology, including behaviors such as the “kelping” mimickery, cruising, & resting, as well as their active predator avoidance of burying and their diet of mysids based on field observations & confirmed through gut content analysis. I uncovered a specific distribution pattern spatially along the coast adjacent to underwater canyons, and temporally from July through February. This study was also able to establish a growth rate for the YOY, finally determined their planktonic larval duration vi around 24 days, and the morphological color changes from black to orange. This study is the first of its kind to examine the YOY of this endangered species making it a key component to their life history, and a baseline for future work on S. gigas and similar long-lived and slow-growing species. vii Introduction In most marine ecosystems worldwide, overfishing is obviously the most devastating cause of the removal of large predatory fishes from ecological communities. Knowledge of life history, such as age and growth, of such a target fish species is the starting point for any effective management frame work (King & MacFarlane 2003), and is crucial to the sustainability of that species. Specifically early developmental processes and recruitment patterns are crucial for completing the life history for any species, allowing us to make increasingly intelligent decisions about current fisheries management policies as well as future conservation efforts (Cailliet et al. 1996, Craig et al. 1999, Myers & Worm 2003). Basic life history information is also a staple in the scientific community and necessary before any hypothesis or conclusions can be made through experimentation. Large brown algae such as the giant kelp, Macrocystis pyrifera, dominates in the southern California waters and creates an underwater forest which allows for multitude of species to thrive amongst the numerous niches created (Feder 1974, Graham 2004, Stephens 2006). Giant Sea Bass (GSB), Stereolepis gigas, were once extremely common in these southern California kelp forests (Crooke 1992) and can be seen on occasion, just outside the kelp forest walls as the apex tertiary carnivore of this system (Cross & Allen 1993, Horn & Ferry-Graham 2006, House et al. 2016). GSB feed on a variety of kelp forest species from small crustaceans to larger fish species such as the California sheephead, kelp basses, perches, rockfish, small sharks, squid, sargo, ocean whitefish, octopus, spiny lobsters, crabs, snails, cephalopods, and other 1 macroinvertebrates (Eschmeyer et al. 1983, Domeier 2001, Horn & Ferry-Graham 2006, Love 2011). In its adult form, the GSB is the largest near-shore teleost off the southern California coast (Pondella & Allen 2008, Hawk & Allen 2014) (Figure 1) found ranging from depth of 5-46 meters (Love 2011). GSB may look similar to a grouper in the family Serranidae, however they are actually a member of the small family of wreckfishes (Polyprionidae) (Shane et al. 1996). They have a wide range found from Humboldt Bay to Baja California, but can be found in relatively high concentrations south of Point conception, from the Channel Islands south, and along the coast (Miller & Lea 1972, Love 2011, House et al. 2016).They have been historically recorded at over 250 kg (Domeier 2001) and estimated to live up to 76 years old (Hawk & Allen 2014), but recent studies have them reaching a length of almost 275 cm (9 ft.) and a weight 381 kg (839 lbs.) (House et al. 2016). This new information is closer to historical reports of fish living between 90-100 years and weighing over 270 kg (Fitch & Lavenberg 1971), and some even as large as 360 kg (Holder 1910). Historically GSB have been targets for both recreational and commercial fishermen since the 1800’s (Pondella & Allen 2008) due to their massive size and the fact that they can also be observed in large semi-predictable aggregations (Sadovy de Mitcheson et al. 2008). These aggregations --believed to be spawning aggregations-- occur during the summer months (Crooke 1992, House et al. 2016) had often been targeted by fishermen, (Meyers & Worm 2003), landing relatively high catches (Crooke 1992), and even up to 255 fish in three days (Domeier 2001). Targeting aggregations can lead to an “illusion of plenty”, usually ending in a population crash (Sadovy & Domeier 2005, Sadovy de Mitcheson et al. 2008, Erisman et al. 2011). Targeting a 2 species can directly affect the genetic diversity, abundance, and size structure of that species (Pauly et al. 1998, Bianchi et al. 2000, Hauser et al. 2002, Dayton et al. 2003), and the direct removal of these apex predators can cause drastic shifts in the ecosystem’s community diversity (Jackson et al. 2001). The once economically important fishery was soon devastated as their catch rates began to fall dramatically in the early 1900s. In fact, in 1934 the commercial catches were close to 114,000 kg until a rapid decline to less than 15,000 kg not more than two years later (Pondella & Allen 2008) (Figure 2). In 1981 the California State Legislature created a moratorium prohibiting the recreational take and limiting commercial take of GSB, which came into effect in 1982. This essentially closed the commercial and recreational fisheries, except for a two-fish per trip bycatch allowance for commercial fishers, later amended to one in 1988. Additionally, Prop 132, known as the Marine Resources Protection Act, was passed in 1994 to close the gill and trammel net fisheries near shore and eventually the GSB were placed on the International Union for Conservation of Nature red list as critically endangered species (Cornish et al. 2004). The GSB populations remain protected but depressed compared to historical values, however, the population does appear to be recovering slowly (Pondella & Allen 2008, House et al. 2016). Estimations of their effective populations size remain around 500 (Chabot et al. 2015), they have been observed more frequently in the last 15 years (Pondella & Allen 2008), with juveniles continuously being caught and released in the recreational fisheries (Baldwin & Kaiser 2008). It is usually uncommon to find evidence of a slow growing long-lived tertiary carnivore species recovering after such heavy fishing pressure (House et al. 2016), however the quarterly surveys conducted by the Vantuna Research group of Occidental college, finally showed an increase in 3 the population after almost 30 years (Pondella & Allen 2008) (Figure 3). Therefore, S. gigas may be an excellent model of recovery for long lived slow growing fishes when the proper management is implemented. The depressed populations in the wild have hindered the ability to complete numerous aspects of the life history of the GSB. They are believed to reach sexual maturity around 11-13 years (Fitch & Lavenberg 1971), but currently there have not been any studies that confirm this estimation. They are oviparous, broadcast spawners with planktonic eggs (Crooke 1992, M oser 1992), believed to spawn during the warmer water months (Peres & Klippel 2003) and recently there is evidence to suggest they do so in pairs (Hovey 2001, Clark unpublished data). The larvae remain in the plankton for an unknown period of time known as the planktonic larval duration (PLD). After transformation from their larval body morphology, they recruit to near shore areas as young-of-the-year (YOY) (Love 2011).