Aquaculture Nutrition doi: 10.1111/j.1365-2095.2012.00963.x 2013 19; 312–320 .............................................................................................. 1 2 2 1 School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Seward, Alaska, USA; 2 School of Fisheries and Ocean Sciences, Juneau Center, University of Alaska Fairbanks, Juneau, Alaska, USA approaches to meet that demand by enhancing or restoring depressed fisheries (Lorenzen et al. 2010). Progress in crus- We conducted large-scale production trials in Seward, tacean aquaculture has allowed for stock enhancement of Alaska, USA to investigate effects of dietary astaxanthin crab and lobster species worldwide (Bannister & Addison supplementation on survival, growth and shell colouration 1998; Agnalt et al. 1999; Secor et al. 2002; Davis et al. of recently settled juvenile (C1–C4) red king crabs (Para- 2005a; Zmora et al. 2005; Stevens 2006b; Bartley & Bell lithodes camtschaticus). We supplemented a control diet of 2008; Cheng et al. 2008). Despite this progress, applications commercial crustacean feeds with astaxanthin, and fed of hatchery technology to stock enhancement are often lim- these diets to juvenile king crabs at densities of 2000 and ited by challenges including economic feasibility of juvenile À 4000 crabs m 2 for 56 days. We assessed survival and production and post-release survival (Blakenship & Leber growth by counting crabs and individually measuring cara- 1995; Bell et al. 2005; Lorenzen 2008). pace width and weighing crabs at the start and end of the Red king crab (Paralithodes camtschaticus, Tilesius 1815) experiment, and quantified crab colour (hue, saturation, was one of the most important fisheries in Alaska, USA; brightness) in digital photographs. Diets containing asta- however, many populations remain depressed despite fish- xanthin had higher survival, suggesting that astaxanthin ery closures (Stevens et al. 2001; Woodby et al. 2005). may provide nutritional or immune system benefits. Crabs Stock enhancement has been proposed as a possible popu- had lower hue, higher saturation and lower brightness val- lation recovery tool for red king crabs because they are ues when fed diets containing astaxanthin, suggesting that some of the most commercially valuable crustaceans in the red king crab colouration is plastic and responds to diet. world, and recruitment limitation has been proposed to Astaxanthin is likely an important dietary component for explain their lack of recovery in the absence of fishing hatchery or laboratory reared red king crab juveniles, and (Blau 1986). The Alaska King Crab Research Rehabilita- should be considered for aquaculture and other rearing of tion and Biology (AKCRRAB) programme was created in this and possibly other crustacean species. 2006 to assess the feasibility of stock enhancement for king crabs in Alaska and expanded on previous rearing technol- KEY WORDS: astaxanthin, crustacean, Paralithodes camtsch- ogies (Nakanishi & Naryu 1981; Nakanishi 1987, 1988; aticus, red king crab, stock enhancement Epelbaum et al. 2006; Kovatcheva et al. 2006; Stevens 2006a,b). Since its inception, the AKCRRAB programme Received 14 September 2011; accepted 13 March 2012 is the first and only US aquaculture programme to success- Correspondence: Benjamin Daly, School of Fisheries and Ocean Sciences, fully demonstrate that king crabs can be cultured on a University of Alaska Fairbanks, 201 Railway Avenue, Seward, AK large-scale in a hatchery setting (Daly et al. 2009). 99664, USA. E-mail: [email protected] As king crab stock enhancement through hatchery pro- duction becomes a possibility, it is increasingly important to understand ecological competence of artificially reared juvenile red king crab. Artificial rearing conditions (i.e., The growing global demand for seafood has increased pres- artificial substrate, flow conditions, diet, lighting) may sure on fish stocks (Pauly et al. 1998). Aquaculture and impact behaviour and morphology, or reduce brain devel- stock enhancement have been suggested as possible opment as seen in other crustacean species (Sandeman & .............................................................................................. ª 2012 Blackwell Publishing Ltd Sandeman 2000; Davis et al. 2005b). The literature is rich Astaxanthin is ubiquitous in marine environments with examples of behavioural and morphological differ- because it is synthesized by phytoplankton and zooplank- ences between hatchery and wild fish (see Huntingford ton and bio-accumulates throughout the food web (Anders- 2004; Brown & Day 2002 for a review) and crustaceans son et al. 2003; Harmon & Cysewski 2008). Astaxanthin is (Davis et al. 2005b; van der Meeren 2005; Young et al. the predominant carotenoid in many crustaceans (Herring 2008). However, some behavioural or morphological defi- 1972, 1973) and is incorporated into the body tissue as it ciencies may be mitigated through conditioning or moves from the digestive system to the epidermis, which improved rearing conditions (Davis et al. 2005b; van der adds a red hue to the overall shell colour (Chien & Shiau Meeren 2005; Le Vay et al. 2007; Young et al. 2008). 2005; Tlusty 2005; Tlusty & Hyland 2005; Barclay et al. Hatchery-cultured juvenile red king crabs exhibit colour 2006). Wild red king crabs feed on a wide range of inverte- variation and are generally lighter in colour than wild brate, vertebrate and macroalgae species (Feder et al. 1980; crabs, which are deep orange/red (B. Daly & G. Eckert, Jewett & Feder 1982), suggesting that astaxanthin is likely pers. obs.; Fig. 1). Colour of crustaceans is determined a natural dietary component of juvenile red king crab. Spe- through two pathways, including morphological mecha- cific advantages of dietary astaxanthin for red king crab nisms and a physiological change via chromatophores (Rao remains unknown; however, nutritional benefits (i.e., 1985; Tlusty 2005). Morphological colour change includes improved survival, growth and colouration) may exist as adjustments of pigments within the exoskeleton, and tends observed in fish (Torrissen 1990) and other crustacean to occur over a longer period because of variations in the (Bordner et al. 1986; Howell & Matthews 1991; Dall 1995; amount and distribution of pigment and structure of the Merchie et al. 1998) species. cuticle (Rao 1985; Robison & Charlton 2005). Atlantic Commercial crustacean feeds are not specifically formu- rock crab (Cancer irroratus) and European green crab lated for red king crabs and yield varying survival and (Carcinus maenas) juveniles exhibit ranges of colours that growth rates (Daly et al. 2009). Hatchery diets may lack correspond with surrounding benthic habitat (Palma & Ste- critical nutritional components essential to juvenile red king neck 2001; Todd et al. 2006); however, the mechanism for crabs that are otherwise found in natural diets. An this colour variability remain largely unknown. American improved feeding regime and diet may enhance shell col- lobsters (Homarus americanus) exhibit short-term colour ouration and optimize survival through superior nutrition, response to environmental cues, such as background colour improved immunity (Babin et al. 2010) or decreased canni- and ultraviolet light in laboratory experiments (Tlusty et al. balism by reducing pressure to seek additional nutrients 2009). In addition, lobster shell pigmentation is controlled (Brodersen et al. 1989; Borisov et al. 2007). The objective by carotenoids that occur naturally in their diet (Tlusty of this study was to test the effects of dietary astaxanthin 2005; Tlusty & Hyland 2005). supplementation on survival, growth and shell colouration of juvenile red king crab under typical indoor hatchery grow-out conditions. Twenty ovigerous females were captured with baited com- mercial pots in Bristol Bay, Alaska, during November 2008. Crabs were transported to the Alutiiq Pride Shellfish Hatch- ery in Seward, Alaska and placed in 2000 L tanks containing flow through ambient seawater ranging from 3.3 to 8.3 °C (mean ± SE 4.65 ± 0.07 °C), and fed ad libitum [~20 g chopped herring and squid crabÀ1 twice weekÀ1 (~0.4% body weight dayÀ1)]. Once hatching began, larvae from each female were mixed together and raised in 1200 L cylindrical Figure 1 Colour variation observed for hatchery-cultured and wild tanks for 50 days until the first juvenile instar (C1) stage. red king crabs. Photo by G.L. Eckert. Larvae were fed enriched San Francisco Bay strain Artemia .............................................................................................. Aquaculture Nutrition, 19; 312–320 ª 2012 Blackwell Publishing Ltd nauplii daily. Artemia nauplii were enriched with DC DHA (15 000 lggÀ1), resulting in ~380 lg astaxanthin gÀ1 feed Selco® (INVE Aquaculture, Salt Lake City, UT, USA) (dry weight). This dose is comparable with other studies enrichment media in 100 L cylindrical tanks for 24 h. using dietary astaxanthin supplementation with shrimp and lobsters (D’Abramo et al. 1983; Barclay et al. 2006; Paibulkichakul et al. 2008). The diet mixtures were bound by cooking and then ground; producing moist particles ~400 We initiated the experiment with 15 000 juvenile (C1) red –1000 lm. Proximate composition of the diets was calcu- king crabs, which were reared over a 56-day period starting lated based on reported manufacturer values (Otohime, on 1 June 2009. First juvenile instars (C1) were collected ZeiglerTM, NatuRoseTM) and values from the scientific liter- from larval rearing tanks shortly