1 Testing ocean warming solutions for red abalone Haliotis rufescens mariculture in San 2 Jeronimo Island, Baja California, Mexico: Effects of depth and diet 3 4 5 Jeremie Bauer1, Rodrigo Beas-Luna1, Julio Lorda*2, Luis Malpica-Cruz3,4, Fabiola Lafarga 6 -De la Cruz5; Fiorenza Micheli6, Ricardo Searcy-Bernal7, Laura Rogers-Bennett8, Miguel 7 Bracamontes-Peralta9. 8 9 1Facultad de Ciencias Marinas, Universidad Autónoma de Baja California, Carretera 10 Ensenada-Tijuana 3917, Fraccionamiento Playitas, 22860 Ensenada, Baja California, 11 México 12 2Facultad de Ciencias, Universidad Autónoma de Baja California, Carretera Ensenada- 13 Tijuana 3917, Fraccionamiento Playitas, 22860 Ensenada, Baja California, México. 14 3Instituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California, 15 Carretera Ensenada-Tijuana 3917, Fraccionamiento Playitas, 22860 Ensenada, Baja 16 California, México. 17 4ECOCIMATI, A.C., Av. del Puerto 2270 Colonia Hidalgo, 22880 Ensenada, Baja 18 California, Mexico. 19 5Departamento de Acuicultura, Centro de Investigación Científica y de Educación 20 Superación de Ensenada, Carretera Ensenada-Tijuana No. 3918, Zona Playitas, CP 22860, 21 Ensenada, Baja California, Mexico. 22 6Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950, USA 23 7Instituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California, 24 Carretera Ensenada-Tijuana 3917, Fraccionamiento Playitas, 22860 Ensenada, Baja 25 California, México (Retired). 26 8California Department of Fish and Wildlife and Bodega Marine Laboratory, University of 27 California, Davis, PO Box 247, Bodega Bay, CA 94923, USA 28 9Sociedad Cooperativa de producción Pesquera “Ensenada”. El Rosario, Baja California, 29 Mexico. 30 *Corresponding author. Email: [email protected] 31 Abstract 32 Wild abalone fishery landings have decreased significantly in past decades as global 33 abalone aquaculture has increased drastically shifting production from fishing to farming. 34 In California (USA) and Baja California (Mexico), multiple climatic stressors and 35 overfishing are thought to be responsible for mass mortalities and the significant decline of 36 abalone resources. One alternative for supporting sustainable abalone fishing is captive 37 propagation and subsequent restocking into the wild. To test, inform, and promote 38 innovative sustainable seafood production strategies in the Northeastern Pacific, we 39 designed an experimental mariculture system at San Jeronimo Island, Baja California in 40 collaboration with the local fishing cooperative. Specifically, the aim was to explore the 41 feasibility of rearing red abalone seed, Haliotis rufescens, on a mariculture setting, to 42 achieve a larger size for future local restocking programs. We tested the effects of two 43 different depths for growing abalone, surface and bottom (5 m) and three different 44 macroalgae diets (Macrocystis pyrifera, Ecklonia arborea and a mixed diet of M. 45 pyrifera/Pelagophycus porra) on the survival and growth of juvenile red abalone (32 ± 3.33 46 mm), inside cages attached to a long line system. The experiment lasted 90 days and the 47 red abalone, mean daily increment in shell length was 87 ± 13 µm d-1. The total mean 48 growth in shell length was 7.86 ± 1.13 mm or 2.62 ± 0.38 mm m-1, with 97% survival 49 rate. Depth did not affect abalone growth or survival. There were no significant differences 50 in growth among abalone fed with the three diets; however, E. arborea fed abalone grew 51 more than those fed with M. pyrifera and the mixed diet. Our results indicate than San 52 Jeronimo Island has the potential for red abalone mariculture and that this strategy may be a 53 useful tool in developing climate-resilient abalone restoration solutions aimed at bolstering 54 seafood production. 55 Introduction 56 Rising sea surface temperature and the increased frequency and severity of storms are 57 stressors for the growth of mariculture around the world (Barange & Perry, 2009). This 58 increases are serious concerns for the development of the abalone aquaculture industry. 59 Wild abalone fisheries have decreased significantly in the past decades, from 20,000 metric 60 tons (mt) in the 1970s to only about 6500 mt in 2016/17 (Cook, 2019). Hence, the current 61 worldwide abalone production has drastically changed to farming, from 50 mt in the 1970s 62 to 160,987 mt in 2016/17 (Cook 2016, 2019). A promising solution to reduce the impact of 63 fisheries is the development of conservation and management actions that diversify 64 production activities, such as aquaculture and mariculture. Indeed, aquaculture is 65 highlighted as a potential solution to the problem of food availability and security in the 66 United Nations 2030 Agenda (UN, 2018). 67 In Mexico, one of the most economically and culturally important fisheries is abalone. The 68 abalone fishery takes place on the Pacific coast of the Baja California Peninsula in the 69 states of Baja California and Baja California Sur (Morales-Bojórquez et al., 2008). Even if 70 the worldwide trend is an increase in abalone aquaculture rather than harvesting wild 71 populations, in Mexico, the wild abalone fisheries produce ten times more volume than its 72 aquaculture industry (300 vs 23.5 tm/year; Cook, 2019). Although abalone catches in recent 73 years are less than 5% of its historical maximum, the fishery continues to be economically 74 important throughout the Baja California Peninsula (Guzmán-Del Próo et al., 2013, 2017). 75 However, along the entire coast, fishing has deteriorated due to a combination of multiple 76 stressors such as overfishing, diseases, extreme warming events and hypoxia (Micheli et 77 al., 2012; Ben-Horin et al., 2016; Boch et al., 2018; Sanford et al., 2019). These new 78 oceanic conditions resulted in landings of less than 100 mt from 2012 onwards in the state 79 of Baja California (northern state of the Peninsula) (DOF, 2018). This decline suggests that 80 additional conservation and management actions are needed for the recovery of natural 81 populations. The “National Abalone Rescue” program currently promoted by the Mexican 82 Ministry of Fisheries (INAPESCA) highlights that aquaculture is a strategy that could be 83 used to promote population conservation (DOF, 2018). And therefore, there is an 84 opportunity to develop abalone aquaculture programs in Mexico, to support conservation 85 programs. 86 87 In Ensenada, Baja California, red abalone mariculture has been carried out in the past in 88 different areas. In 1990, Searcy-Bernal and Salas-Garza (1990) conducted the first 89 experimental mariculture project to growth red abalone, H. rufescens , in floating cages in 90 Todos Santos Bay. Around the same years, a commercial red abalone mariculture company 91 "Abulones Cultivados" was established in the vicinities of Todos Santos Island (Preece & 92 Mladenov, 1999). However, the company moved to land-based facilities and still operating 93 until now in the area of Ejido Erendira, as the cost and operation for mariculture activities 94 in those years were high (Searcy-Bernal et al., 2010). More recently, Zertuche-González et 95 al. (2014) evaluated the growth performance of red abalone in an integrated multi-trophic 96 aquaculture (IMTA) farm, for one year, in the San Quintin Bay area. This study proves the 97 feasibility to growth out red abalone juveniles in the sea with an alternative fresh diet 98 (Ecklonia arborea). Now, we know more about the Oceanography of the area and we have 99 better technology to do mariculture. In addition, fishing cooperatives have greater work 100 capacity and the mentality towards aquaculture has been changing over time, due to wild 101 resources scarcity. Hence, we are at an ideal moment to carry out mariculture experiments 102 with the intention of enhancing marine resources in Baja California. 103 104 In the northeastern Pacific, abalone farms typically use the giant kelp Macrocystis pyrifera 105 harvested from the wild as feed (Evans & Langdon, 2000; García-Esquivel & Felbeck, 106 2009). However, in the last two decades extreme temperature and wave events, such as 107 ENSO and marine heatwaves, have substantially affected giant kelp in Baja California 108 (Ladah et al., 1999; Arafeh-Dalmau et al., 2019; Cavanaugh et al., 2019). Hence, it is 109 important to explore the effect of other macroalgae as an alternative abalone food source, to 110 cope with future regional giant kelp population variability. For example, the palm kelp E. 111 arborea is capable of surviving in relatively warm waters (>20º C) with low nutrients 112 where other kelps cannot survive (Hernández-Carmona et al., 2000, 2001; Zertuche- 113 González et al., 2014). On the other hand, storms, hypoxia and heatwaves events can affect 114 mariculture systems. One option against this is to move the cages vertically in the water 115 column and be able to submerge them during these events. Mariculture can increase fishers’ 116 communities’ ability to adapt to these changes by reducing the pressure on wild-caught 117 animals while promoting conservation alternatives to help the restoration of natural 118 populations. 119 120 Wild abalone populations have declined in Mexico and there is now uncertainty in recovery 121 due to climate change impacts on mariculture/restoration production in Baja California. To 122 test the potential for abalone mariculture in San Jeronimo Island, Baja California, Mexico, 123 we explored the feasibility of growing red abalone in cages attached to a long-line system. 124 Specifically, we examined 1) the effect of depth, surface and bottom (5 m), and 2) the 125 effect of three different brown macroalgae diets in the growth and survival of red abalone 126 juveniles. Lowering cages in the water column and reducing M. pyrifera are two strategies 127 which could bolster mariculture under ocean warming conditions in the region but which 128 require rigorous testing. 129 130 Materials and methods 131 Experimental study area 132 The study was carried out at San Jeronimo Island located in Ensenada Municipality in the 133 state of Baja California, Mexico (Fig.