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Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Author's personal copy Fisheries Research 129–130 (2012) 28–37 Contents lists available at SciVerse ScienceDirect Fisheries Research jou rnal homepage: www.elsevier.com/locate/fishres Annual brood number and breeding periodicity of squat lobsters (Decapoda: Anomura: Galatheidae) from the continental shelf of the SE Pacific—Implications for fisheries management a,b,∗ a a b Martin Thiel , Nuxia L. Espinoza-Fuenzalida , Enzo Acuna˜ , Marcelo M. Rivadeneira a Facultad Ciencias del Mar, Universidad Católica del Norte, Larrondo 1281, Coquimbo, Chile b Centro de Estudios Avanzados en Zonas Áridas, CEAZA, Coquimbo, Chile a r t i c l e i n f o a b s t r a c t Article history: The reproductive potential of a population depends on the number of broods that individuals produce Received 3 January 2012 during the annual reproductive season. Determining the annual brood number is especially relevant for Received in revised form 17 April 2012 species that are actively fished. Herein we combined different approaches to estimate the annual brood Accepted 6 June 2012 number of two commercially exploited species of squat lobsters from the Chilean continental shelf and upper slope, Cervimunida johni and Pleuroncodes monodon. Long-term maintenance in the laboratory Keywords: revealed that most females (>70%) produced 3 or more broods during the annual reproductive season. Squat lobsters Incubation of individual broods required about 40 days, which would allow for 3 subsequent broods Trawl fishery during the main reproductive period (June–September). The dynamics of brood release of ovigerous Fisheries management Reproduction females that were collected from the field at approximately monthly intervals supported the estimate Annual brood number of 3–4 annual broods for adult females. Furthermore, these latter data also indicated a high degree of Mating synchrony breeding synchrony among reproductive females. It is suggested that the production of successive broods might be an adaption to the variable oceanographic conditions during the reproductive period, ensuring that at least one larval cohort finds favorable conditions for development and settlement. Based on these results it is recommended that fishing effort is reduced during the main reproductive period of the two squat lobsters. © 2012 Elsevier B.V. All rights reserved. 1. Introduction proportion of the adult population that is reproductive, and fecun- dity and first sexual maturity of females. However, life history traits Fisheries of crustaceans from the continental shelf and slope such as the number of broods produced during the annual repro- have been developed and intensified during the past decades. Some ductive period cannot be easily obtained from catch data. species, such as the Norway lobster Nephrops norvegicus (see Aguzzi Indirect measures such as the relationship between massive et al., 2003) or the rose shrimp Aristeus antennatus (see Sardà et al., molting events and the seasonally changing proportion of oviger- 2003) are exposed to intense trawl fisheries down to about 500 ous females have been used to infer the duration of embryo or 1000 m depth, respectively. Management of these fisheries is incubation and the frequency of brood production (e.g. in Nephrops mainly based on information obtained from commercial catch data. norvegicus – Sardà, 1991). In species where mating occurs dur- While valuable, these data provide little information on feeding ing the intermolt period, this inference is complicated, and direct habits, ecological interactions or the behavior of the respective observations are required to estimate the number of broods a species. However, this biological information is of great importance female can produce during a given reproductive season. Reli- for management decisions. able estimates of annual brood production (together with female One of the least known components of the biology of crustaceans fecundity) are important in order to (i) determine the population from the continental shelf is their reproductive behavior. Infor- reproductive output, and (ii) identify sensitive periods during the mation that is commonly available (because it can be extracted reproductive season. from catch data) is the duration of the reproductive season, the Various approaches have been used to estimate the annual brood number of females. Most studies used field-based samplings and seasonal estimates of the proportion of ovigerous females (e.g. ˇ ∗ Fukui and Wada, 1986; Stevciˇ c,´ 1988; Omori et al., 1997; Kyomo, Corresponding author at: Facultad Ciencias del Mar, Universidad Católica del 2002). Other studies examined the relationship between gonad Norte, Larrondo 1281, Coquimbo, Chile. E-mail address: [email protected] (M. Thiel). maturation and appearance of ovigerous females (e.g. Minagawa, 0165-7836/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fishres.2012.06.004 Author's personal copy M. Thiel et al. / Fisheries Research 129–130 (2012) 28–37 29 1997; Sardà, 1991; Orsi-Relini et al., 1998; Gelpi et al., 2009). In the May and November). The fishing grounds were on the continental ◦ deep-sea shrimp Aristeus antennatus the close relationship between shelf and upper slope (100–250 m) off Coquimbo, Chile (30 S). Once molting, mating and brood production led to the inference that the catch was on deck, adult individuals were sorted out, placed in females produce at least three broods during the annual repro- large coolers with seawater, and transported to the seawater labo- ductive period (Demestre, 1995). For squat lobsters, Dellatorre ratory of Universidad Católica del Norte, where they were placed in and Barón (2008) elegantly showed that Munida gregaria females large holding tanks with running seawater. Squat lobsters for the incubating advanced embryos also had ovaries in advanced devel- laboratory experiments were usually collected from the last hauls opmental stages, indicating that these females produced two or of the day, in order to reduce handling and transport time as much three subsequent broods. as possible. Individual females can also be maintained throughout the repro- Of each monthly sample we selected 60 ovigerous females ductive period in the laboratory to estimate the annual brood (22–42 mm carapace length CL in both species) and up to 49 non- production. For example, several large decapod species that are ovigerous females (21–37 mm CL in C. johni and 23–34 mm CL in P. commercially exploited were shown in laboratory experiments to monodon); during the peak of the reproductive season most females produce two or more annual broods (Shields et al., 1991; González- were ovigerous and consequently fewer than 60 non-ovigerous Gurriarán et al., 1998; Hines et al., 2003). While providing valuable females (desired number) were available. Furthermore, we main- information, long-term maintenance of females in laboratory tanks tained large males for the mating experiments (25–46 mm CL in C. might influence their brood production. Lack of reproductive males johni, n = 334 males; and 28–43 mm in P. monodon, n = 79 males). and/or sperm could suppress the female reproductive potential Squat lobsters were fed ad libitum with fish remains, clams, ascid- (Hines et al., 2003). On the other hand, ad libitum food supply might ians and other carrion. Food remains were cleaned and replaced generate better feeding conditions for females maintained in lab- with fresh food every 3 days. oratory environments than encountered by females in the natural During the study period, water temperature in the laboratory ◦ ◦ environment, thereby possibly enhancing the brood production of ranged between 11 C and 13 C, which is comparable to the tem- laboratory females. This highlights the importance of comparing peratures on the main fishing grounds in the region (in July 2006 ◦ ◦ the reproductive potential of long-term laboratory inhabitants with temperatures ranged between 11 C and 12 C on the continen- that of females collected in the field (see also Hines et al., 2003). tal shelf off Coquimbo at water depths of 100–200 m, J. Sellanes One of the groups for which annual brood numbers are poorly personal communication). known is squat lobsters (Thiel and Lovrich, 2011). This information, however, is especially relevant for those species that are commer- 2.2. Estimating brood number of females in long-term laboratory cially exploited or prospected for future exploitation. Two squat experiments lobster species (Cervimunida johni and Pleuroncodes monodon) from the continental shelf and upper slope off Chile have been commer- Reproductive (=ovigerous) females from the field were held in cially exploited for about five decades. Dramatic declines of squat the laboratory throughout the entire reproductive period to esti- lobster stocks during the past decades had led to a diverse range of mate the number of annual broods (Fig. 1). We maintained females management measures, including complete or temporal closures of as long as they produced new broods: a female was considered the fisheries (Bahamonde et al., 1986; Roa and Bahamonde, 1993; as having produced its last brood once it had been with males in Acuna˜ et al., 1998). pairing (or mating) tanks for a continuous period of 6 weeks with- The fact that a large proportion (80–100%) of the adult females out producing a new brood.