Jasus Edwardsii Biology And Fishing Industry Biology Essay

Introduction

Fisheries play an important role in the global provision of food, directly accounting for at least 15% of the animal protein consumed by humans (Muir 2012). Human populations are continuing to grow and an increased need for animal protein has led to a higher demand for fish as a source of food. Despite this increased need for fish protein, global marine fisheries catches have declined in recent decades and at least 28% of the world’s fish stocks are described as overexploited or depleted (Mora, Myers et al. 2009). Declining finfish catches have led to increased interest in the enhancement of invertebrate fisheries. Since 1950, the total reported catch of invertebrates has increased 6-fold from 2 to 12 million tons, and 18% of invertebrate fisheries are already fully exploited, 21% over-exploited or restrictively managed, and 13% have collapsed or are currently closed (Anderson, Flemming et al. 2011). In order to prevent further declines in these fisheries and ensure sustainable development of invertebrate fisheries, there is an urgent need for a robust scientific basis upon which to base management recommendations. Global fishing industries need rigorous scientific assessment for precautionary management and sustainable exploitation to ensure the long-term resilience of fished populations and ocean ecosystems.

Jasus edwardsii biology and fishing industry

The southern rock lobster Jasus edwardsii (Hutton 1875) (Palinuridae) inhabits rocky reefs, between 1 m and 200 m depth along the coastlines of southern Australia, Tasmania and New Zealand. In New Zealand, its range extends from Three Kings Islands in the north (34° S, 172° E) to the Auckland Islands in the south (51° S, 166° E), and to the Chatham Islands in the east (44° S, 176° W; Kensler 1967). The lobsters are active after sunset and leave their shelters to feed on urchins, crabs and other crustaceans, as well as gastropods, chitons and bivalves (Fielder 1965). Moulting occurs one to two times a year, in spring and autumn, with mature females only moulting in autumn to winter and mature males generally moulting in spring (Annala & Bycroft 1988). The increase in carapace length at moulting ranges from 2 to 14 mm (McKoy 1985; Annala & Bycroft 1988). Adult lobsters can reach sizes of over 160 mm carapace length (CL) for females and 200 mm CL for males (MacDiarmid 1991). The size at onset of maturity is highly variable between locations, ranging from 72 to 171 mm CL and the age at maturity ranges from 3 to 12 years (Annala, McKoy et al. 1980).

The Jasus edwardsii fishery is currently the most economically valuable inshore fisheries for New Zealand worth over NZ$230 million to the NZ economy (www.fish.govt.nz). The current markets are primarily China, Japan, Hong Kong and Taiwan for live lobsters and the United States for frozen tails. The fishery is divided into 10 CRA zones, which are further divided into 43 statistical zones for stock assessment, but the currently zone management strategy isn’t based on the species biology. Thus, ultimate goal of this PhD project is to support the existing fishery by ensuring the well-being of wild populations. The aims of my PhD are:

To determine population genetic structure and analyze connectivity patterns of Jasus edwardsii by developing a single nucleotide polymorphism (SNP) panel via restriction site-associated DNA sequencing (RADSeq);

To reassess size at onset of maturity in female Jasus edwardsii thought New Zealand and determine changes over time;

To evaluate human-induced evolution caused by selection through selective harvest of desired phenotypes;To assess impact of population density and habitat characteristics on recruitment rates.

Chapter 1: population genetic structure and settlement patterns of Jasus edwardsii

Jasus edwardsii has been shown to have one of the longest-lived larval durations of any marine species – up to 24 months (Booth 1994), which would be expected to support large-scale dispersal and significant gene flow between populations. In order to understand the fluctuations in adult population abundance we must understand mechanisms affecting recruitment variability and larval dispersal (Chiswell and Booth 2008). Drifting with currents was suggested to be the main driver of the early- and mid-stage phyllosoma distribution, however it does not explain the distribution of the late-stage phyllosomas and pueruli (Chiswell and Booth 2005, Chiswell and Booth 2008). Pueruli have been shown to be active swimmers (Jeffs 2001), so once they reach the continental shelf their movements are deliberate and dispersal is affected by numerous factors: underwater sound, water chemistry, eddychemotaxis, osmoreception, salinity, magnetic fields, celestial cues, electrosense and specific behavior (Cobb 1997, Jeffs, Montgomery et al. 2005). Processes affecting larval supply have great effects on adult stocks and subsequently represent great importance to population dynamics and resource management. Modeling of such a complex process is currently beyond the scope of bioinformatics and existing models can’t be used for fine assessment of larval dispersal and settlement. One of the assumptions underlying current management of the rock lobster fishery is that stock is comprised of a single, genetically homogeneous population. However, recently Thomas & Bell (2013) described 3 genetically distinct subpopulations of Jasus edwardsii based on assessment of 7 populations from five CRA zones in New Zealand using 8 microsatellite markers. By using higher resolution methods and conducting more extensive sampling throughout New Zealand we will be able to identify any finer-scale genetic population structure. Thus, there are 3 aims to this project: a) establish a panel of SNP markers for Jasus edwardsii; b) enhance our knowledge of existing stock structure by analyzing samples from approximately 30 different locations around New Zealand; c) analyze population structure of Jasus edwardsii larvae and conduct assignment tests to track potential larval dispersal and model settlement process. Analysis of settlement patterns of RL project involves the development of a panel of SNP markers using ddRADSeq approach (Etter, Bassham et al. 2011). I will analyze up to 30 populations from different sampling locations around New Zealand to define adult subpopulation patterns. In addition, we will analyze larvae subpopulation structure using established SNPs markers and by correlation of this data with adult population structure I will be able to track larval dispersal and settlement process in Jasus edwardsii (Glover, Hansen et al. 2010).

Chapter 2: reassessment of size at onset of maturity in female Jasus edwardsii

The size at the onset of sexual maturity (SOM) is an important biological characteristic used in the management of many exploited species. It is important for determining minimum size limits for females in rock lobster fishery to make sure that most animals in the population have the opportunity to breed at least once before being recruited to the commercial fishery (Ryan 1997).

SOM is thought to vary because of a number of factors including temperature, growth rate, age, metabolic rate, population density, food availability, and other environmental factors (Annala, McKoy et al. 1980). Temperature has been implicated as a major influence on SOM of local populations of J. edwardsii (Street 1969, (Annala, McKoy et al. 1980), with larger estimates of SOM in warmer areas with faster growth rates compared with colder environments. SOM has been shown to change not only spatially but also temporally. A substantial decline has been reported in SOM over the past 35 years in the rock lobster Panulirus cygnus, which is closely related to Jasus edwardsii in Australia (Melville-Smith and Lestang 2006). The major goal of this project is to evaluate current SOM in Jasus edwardsii in 10 sampling locations around New Zealand and estimate changes in SOM with time. Females will be considered mature if they are bearing external eggs attached to the pleopods, or if they have developed setae on the endopodites of the pleopods (Annala, McKoy et al. 1980). This data will be compared to SOM examined during the period 1960-1980 to identify any changes over time. Sampling will be conducted with pots and ~ 100 individuals will be assessed per sampling location.

Chapter 3: fishing-induced selection through harvest of desired phenotypes

Long-term harvesting has been shown to cause selective genetic changes. There is a growing body of evidence showing that the harvesting of phenotypically desirable animals from wild populations causes selection that can reduce the frequencies of those desirable phenotypes (Allendorf, England et al. 2008, Allendorf and Hard 2009, Conover, Munch et al. 2009). To sustain the productivity of harvested populations, it is crucial to take into account possible fishing induced selection effects. Marine species populations which are selectively harvested tend to show substantial declines in fecundity, egg quality, larval size, viability and growth rates (Walsh, Munch et al. 2006). For closely-related to Jasus edwardsii species - Panulirus cygnus commercial removal of larger lobsters has been shown to increase the number of undersized lobsters in the population and caused a substantial decline in average size at SOM in over the last 35 years (Melville-Smith and Lestang 2006). With earlier onset of maturity female rock lobsters tend to produce larger amounts of eggs (Melville‐Smith, De Lestang et al. 2009). Thus, our primary concern is that as a result of the smaller amount of sperm produced by smaller lobsters (Butler 1999), fishing-induced selection will result in reduced fertilization and higher egg mortality rates in Jasus edwardsii population. Genome scans with high markers density can be a useful tool for investigating local adaptation in natural populations and identification of candidate genes under selection. To test for fishing-induced selection changes in SOM and average size we will examine allele frequencies for loci under selection. We will obtain DNA from ~30 Jasus edwardsii populations across New Zealand. After processing using RADSeq method tagged sequences will be genotyped and assembled using existing data on Jasus edwardsii and closely related species (Everett, Grau et al. 2011). We will detect candidate genes under selection using outlier tests for Fst (Brieuc and Naish 2011, Narum and Hess 2011). Correlation of allele frequencies of genes under selection in different subpopulations with average size and SOM will help us reveal if any fishing-induced selection effects can be found in population.

Chapter 4: impact of population density and environment on recruitment rates

There is a growing body of national and international research showing that Marine Protected Areas (MPA) can have positive effects on the size and abundance of local marine species and promote the recovery of fished populations, particularly in Jasus edwardsii (Davidson, Villouta et al. 2002, Moland, Olsen et al. 2013). Spillover of individuals into the surrounding area is considered to be one of the main benefits of MPAs to fisheries. Increased abundance of adult and juvenile conspecifics has been proposed to locally reduce larvae density and subsequently settlement through enhanced habitat usage (Phillips and Booth 1994). The main aim of this project is to assess impact of population density and environmental conditions on recruitment rates in fished and protected areas. I will establish a small network of larvae collectors inside and outside of several marine reserves. Groups of 3 crevice-type collectors with a minimum distance of 3 m between them will be placed within 2 km of the shore at depths varying from 1 to 12 m. Fresh water runoff, bottom composition, swells and water clarity will be considered before placement. Population density and environmental conditions will be assessed for every location and correlated with recruitment rates will be assessed (e.g. using PRIMER).

Significance of research

The main aim of my work is to address several major problems that might affect long-term sustainability of Jasus edwardsii fishery. Rigorous analysis of population genetics of adult stocks will inevitably lead to better understanding of stock structure and enable the potential establishment of smaller-scale management strategies for separate subpopulations than are currently used. I hope my research will provide recommendations that can help prevent declines in genetic diversity within the species and ensure its ability to survive in changing environment. A better understanding of larval dispersal and settlement will provide insights into stocks structure and assist with management. I hope to be able to define subpopulations that need enhanced protection as major contributors to the stock and subpopulations contributing less to the next generation. These data might also lead to reevaluation of existing stock boundaries and establishment of individual TACC rates for separate areas. Size at onset of maturity is shown to change in some species over significant time periods and reassessment is needed to prove examine the effects of current management strategies. Analysis of genes that are currently under selection in Jasus edwardsii populations will enable us to assess major factors influencing population’s characteristics on gene level. Finally, I will evaluate the contribution of MPA’s through spillover to the fishing industry and by studying settlement rates in areas with different levels of protection and subsequently different abundance of adult lobsters, I hope to be able to understand if MPAs are enhancing the recruitment process. Results of these projects combined will give a solid scientific basis for precautionary management and continued sustainable exploitation.