Improved growth performance and physiological state in hybrid abalone (Haliotis rufescens and Haliotis fulgens) facing ocean acidification conditions

Abalone (Haliotis spp.) is a valuable global aquaculture resource in Mexican abalone industry, particularly red (Haliotis rufescens) and green (H. fulgens) abalone, showing significant growth. However, climate change -particularly ocean acidification (OA)- threatens production by negatively impacting mollusks, leading to recruitment failures, poor fertilization, malformations, and reduced calcification and growth jeopardizing sustainability and food security. This study aims to assess robustness of a hybrid abalone cross RF (H. rufescens ♀ x H. fulgens ♂) to OA conditions by evaluating biological performance (survival, growth in weight and length) and metabolic response (oxygen consumption, ammonia excretion rate, and atomic O:N ratio). Juveniles from hybrid RF cross and two pure parental crosses (RR, FF) were exposed to three pH levels: control (pH ≈ 8.0) and two reduced pH scenarios (pH 7.8 and 7.5), representing moderate and severe OA conditions. The results showed hybrid cross exhibiting better growth and metabolic response than pure crosses under all conditions. Notably, hybrid length growth was superior under moderate OA conditions (pH 7.8) compared to control (pH 8.0) and intense OA conditions (pH 7.5). Enhanced physiological hybrid status was evidenced by increased oxygen consumption and stable ammonia excretion, reflected in higher atomic O:N ratio. This study demonstrates hybrid cross RF robustness under OA conditions and supports interspecific hybridization as potential mitigation strategy to alleviate negative OA effects for sustainable abalone production. The effects of reduced pH seawater associated to ocean acidification conditions on biological performance and metabolic response. Horizontal lines = neutral effect; red arrows = negative effect; and blue arrows = positive effect. Green box corresponds to survival; blue box correspond to variables related with growth (RGRweight and RGRlength; relative growth rates for wet weight and shell length); and yellow box correspond to variables related with energy metabolism (OCR = oxygen consumption rate; AER = ammonia excretion rate, and O:N; atomic ratio oxygen / nitrogen). [Display omitted] •Hybrid vigor in abalones evaluated under future ocean acidification scenarios.•Hybrid cross abalone show positive heterosis on biological performance.•More robust metabolic response observed in hybrids than in pure abalone crosses.•Higher heterosis for survival and shell growth reached at pH 7.8 conditions.•Int