Oreti Beach 2005 toheroa survey : yield per recruit and review of historical surveys.
Beentjes, M.P.
Oreti Beach 2005 toheroa survey : yield per recruit and review of historical surveys. - Wellington : Ministry of Fisheries, 2006. - 47 p. : figs. ; 30 cm. - New Zealand fisheries assessment report ; 2006/36 .
A survey of Oreti Beach toheroa was carried out between 7 and 11 February 2005 with 60 transects being sampled (17 sieved and 43 non-sieved). A two phase random survey design was used with 50 transects in phase 1 and 10 in phase 2. The population estimates were 583 000 legal-sized/adult toheroa (lO0 mm and over), 401 000 sub-legals (40-99 mm), and 6982 000 juveniles (under 40 rom) with c.v.s of 9%, 19%, and 10%, respectively. The required survey target c.v. for legal-sized toheroa was 20%. The juvenile population estimate was from sieved transects only. Historical population estimates were made for toheroa 80 mm and over and the 2005 estimate was 714 000 with c.v. of II %. The length frequency distribution was characterised by a strong mode of juvenile toheroa, and a less pronounced mode from 100 to 125 mm, with relatively few sub-legal toheroa between these modes. Toheroa were found in all strata. but adults were not found in the middle (east-west) of the beach. and were most abundant in the southeast end. i.e., 90% of adults were found in the first 3 km of the beach. Juveniles were evenly distributed along the entire beach. with a slight southeast bias. The size groups occupied different zones between high and low water with adults and sub-legals about 100 to 200 m (adult mean = 155 m, sub-legal mean = 144 m) below high water. and juveniles wjlh a very wide range from 20 to 320 m (mean = 102 m). Of the 2478 quadrats sampled. 98% has substrate suitable for toheroa (sand or coarse sand).
1175-1584
TOHEROA
FISHERY SURVEYS
ORETI BEACH
ABUNDANCE
STOCK ASSESSMENT
Oreti Beach 2005 toheroa survey : yield per recruit and review of historical surveys. - Wellington : Ministry of Fisheries, 2006. - 47 p. : figs. ; 30 cm. - New Zealand fisheries assessment report ; 2006/36 .
A survey of Oreti Beach toheroa was carried out between 7 and 11 February 2005 with 60 transects being sampled (17 sieved and 43 non-sieved). A two phase random survey design was used with 50 transects in phase 1 and 10 in phase 2. The population estimates were 583 000 legal-sized/adult toheroa (lO0 mm and over), 401 000 sub-legals (40-99 mm), and 6982 000 juveniles (under 40 rom) with c.v.s of 9%, 19%, and 10%, respectively. The required survey target c.v. for legal-sized toheroa was 20%. The juvenile population estimate was from sieved transects only. Historical population estimates were made for toheroa 80 mm and over and the 2005 estimate was 714 000 with c.v. of II %. The length frequency distribution was characterised by a strong mode of juvenile toheroa, and a less pronounced mode from 100 to 125 mm, with relatively few sub-legal toheroa between these modes. Toheroa were found in all strata. but adults were not found in the middle (east-west) of the beach. and were most abundant in the southeast end. i.e., 90% of adults were found in the first 3 km of the beach. Juveniles were evenly distributed along the entire beach. with a slight southeast bias. The size groups occupied different zones between high and low water with adults and sub-legals about 100 to 200 m (adult mean = 155 m, sub-legal mean = 144 m) below high water. and juveniles wjlh a very wide range from 20 to 320 m (mean = 102 m). Of the 2478 quadrats sampled. 98% has substrate suitable for toheroa (sand or coarse sand).
1175-1584
TOHEROA
FISHERY SURVEYS
ORETI BEACH
ABUNDANCE
STOCK ASSESSMENT