The search for biomarkers in the growth prediction of the West Coast Rock Lobster, Jasus lalandii

Thesis (PhDAgric)--Stellenbosch University, 2022.ENGLISH ABSTRACT: The West Coast rock lobster (WCRL) Jasus lalandii is a key ecological species and an important fisheries resource in South Africa. The resource is heavily depleted to 1.8% of pristine levels. The fishery is managed according to an operational management procedure to sustainably rebuild the stock, using an annual catch limit and effort control, determined from Catch per Unit Effort, fisheries independent abundance index and growth data. Since these derive from the preceding season, the present research aimed to identify timelier predictors for the next season. The first part of this study analysed biological parameters of male and female WCRL of male commercial size over two years to determine reserve accumulation during two growth (moult) and reproductive (ovarian) cycles. A historically fast-growth- and a slow-growth area were compared - in relation to their annual male somatic growth rate. Moreover, moult stage and biochemistry of hepatopancreas and ovaries were investigated from the fast growth area. The second part specifically investigated reserve accumulation in the high-growth area with a focus on lipid reserves. The study confirmed that annual growth increment in Hout Bay is still about 1 mm higher than at Olifantsbos and inter-annual differences persist within areas. Growth remains at the low level that continues since 1987, indicating that factors for slow growth persist. Results also confirmed seasonal reserve accumulation in male hepatopancreas in preparation for moult/growth in both areas, whereas there was no such seasonality in female hepatopancreas. Concomitant with male hepatopancreas size, female gonad size increased from a minimum in winter to a maximum shortly before spawning. Reserve accumulation varied inter-annually and in extent and timing for both genders. Lipids and proteins accumulated during the moult cycle in male hepatopancreas and in ovaries but not in female hepatopancreas. During the ovarian cycle, reserves accumulated in the ovaries but not in the female hepatopancreas. Some indications of an involvement of the female abdominal muscle in reproduction (ovary maturation) were revealed: It is up to 8% of body size larger than in males and its size declines as ovary cycle progresses. During ovary maturation, females from the Hout Bay area had 42 – 120% more lipids available (total in hepatopancreas and ovaries) than males, meaning that a) females have a higher food consumption rate, b) the area provides sufficient food to support both growth and reproduction, and c) there is surplus food available for males to support optimal somatic growth. In conclusion, females do not need to (completely) prioritise partition of reserve between growth (ovary) and reproduction (hepatopancreas) in this area. The fatty acid profile of male and female hepatopancreas and female gonads did not change during accumulation and no changes in fatty acid profiles occurred during both moult- and reproductive cycles. Presumably, the quality of the available food in the fishing area is unchanged during reserve accumulation and optimal for growth and reproduction. The project aimed at the identification of potential predictors for male somatic growth as an input for annual catch determination. Based on the prerequisite that a potential predictor must display distinct seasonal variation, several parameters were investigated. However, many of them, such as moult stage and fatty acid profile were found unsuitable. Only three sets of data emerged that have the potential to serve as future predictors: 1) lipid accumulation for growth in the male hepatopancreas, 2) reserve accumulation for reproduction in the female gonads and 3) the difference between male and female lobsters in total available lipids. Only 1) correlated well with growth increment during subsequent moult in the area. However, 2) and 3) have strong potential but require additional research. Although these results are not yet robust enough to qualify for the use in stock assessment, they provide important initial information for the development of a predictor for male growth increment in the subsequent moult. The project also produced important information to design a future research strategy to answer remaining questions and provide further advice for fisheries management of the WCRL resource.AFRIKAANSE OPSOMMING: Die Weskus rotskreef (WCRL), Jasus lalandii, is ‘n ekologies sowel as ekonomies belangrike kreefspesie in Suid-Afrika. Huidige getalle van die spesie is slegs sowat 1.8% van die vlakke wat verwag sou word in ongerepte toestande. Die verwydering van die kreefspesie word tans streng bestuur om in ‘n volhoubare poging om getalle van die spesie te laat toeneem. Aangesien jaarlikse limiete bereken word deur gebruik te maak van die vorige jaar se data, is die doel van hierdie navorsing om akkurate voorspellings vir die volgende seisoen te vergemaklik. In die eerste gedeelte van die studie is die biologiese parameters van manlike sowel as wyfie krewe met kommersiële grootte bo 2 jaar ouderdom gebruik om reserwe opeenhoping gedurende twee groei -(dop verwerp) en voortplantingsiklusse te bepaal. Data vanaf histories vinnig sowel as stadige groei areas is vergelyk in verhouding met die jaarlikse manlike somatiese groei tempo. Die groei (dop verwerp) sowel as biochemie van die hepatopankreas en eierstokke in die area met vinnige groei is bestudeer. In die tweede deel van die studie, is spesifiek gefokus op reserwe lipied akkumulasie in die area met vinnige groei. Die studie het bevind dat die jaarlikse toename in die Houtbaai area ongeveer 1 mm hoër is as in die Olifantsbos area. Jaar tot jaar verskille volhard in die verskillende areas. Die lae groeivlakke soos waargeneem sedert 1987 duur voort wat aandui dat die faktore wat ‘n lae groeitempo veroorsaak, nog steeds teenwoordig is. Resultate bevestig ook seisoenale reserwe opeenhoping in manlike hepatopankreas ter voorbereiding vir die groei (dop verwerp) fase. In teenstelling hiermee, is geen seisoenale opeenhoping in die vroulike hepatopankreas waargeneem nie. Jaar tot jaar variasie in die omvang sowel as tydsintervalle van reserwe opeenhoping is in beide geslagte waargeneem. Gedurende die groeifase, is die opeenhoping van lipiede sowel as proteïene in manlike hepatopankreas sowel as vroulike eierstokke waargeneem. Geen opeenhoping is waargeneem in vroulike hepatopankreas nie. Gedurende die ovariale siklus vind reserwe opeenhoping plaas in die eierstokke, maar nie in die vroulike hepatopankreas nie. ‘n Mate van betrokkenheid van die vroulike abdominale spier is waargeneem in voortplanting (rypwording van die eierstokke). Die vroulike abdominale spier is tot 8% groter as by die manlike kreef, en die grootte neem af soos wat die ovariumsiklus vorder. Tydens die ovariumsiklus was die lipiedvlakke by vroulike krewe in die Houtbaai area (totaal in hepatopankreas sowel as eierstokke), 42 – 120% hoër as by manlike krewe. Die hoër vlakke by die vroulike krewe, beteken, a) hoër tempo van voedselopname, b) genoegsame nutriënte in die area om groei sowel as voortplanting te ondersteun, c) surplus voeding vir manlike krewe beskikbaar om optimale somatiese groei te bevorder. Ter afsluiting, blyk dit dat daar minimale noodsaaklikheid is vir die partisie van reserwes tussen ovarium en hepatopankreas by wyfie krewe in die area. Daar was geen verandering in die vetsuurprofiele van mannetjie en wyfie hepatopankreas sowel as eierstokke van die wyfies tydens groei- en voortplantingsiklusse. Die kwaliteit van beskikbare voeding in die area, is waarskynlik onveranderd tydens die opeenhoping van reserwes en is optimaal vir groei en voortplanting. Die doel van die projek was die identifikasie van potensiële voorspellingsmeganismes vir somatiese groei by mannetjie krewe as inset vir die bepaling van jaarlikse vangs limiete. Die voorvereiste vir ‘n potensiële voorspellingsmeganisme is dat daar duidelike seisoenale variasies moet voorkom en daarom is verskeie parameters tydens die studie ondersoek. Daar is egter bevind dat verskeie parameters, soos die groeifase (vervel) sowel as vetsuurprofiele nutteloos was. Drie stelle data is bevind as potensiële toekomstige voorpellingsmeganismes: 1) opeenhoping van lipiede vir groei in manlike hepatopankreas, 2) reserwe opeenhoping vir voortplanting in vroulike geslagskliere en 3) die verskil tussen mannetjie en wyfie krewe in totale beskikbare lipied vlakke. Slegs 1) korreleer goed met ‘n toename in groei gedurende die daaropvolgende dop verwerp fase in die area. Punte 2) en 3) toon goeie potensiaal maar verdere navorsing is nodig. Alhoewel die studie resultate nie robuus genoeg is om gebruik te word vir die voorspelling van getalle nie, is daar voldoende aanvanklike inligting vir die ontwikkeling van ‘n voorspellingsmeganisme vir ‘n toename in groei van die manlike spesie. Die resultate van die projek voorsien ook belangrike inligting vir toekomstige navorsing rakende die bestuur van die Weskus Rotskreef hulpbron.Doctora